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  • Articles  (214)
  • Saccharomyces cerevisiae  (109)
  • immobilization  (109)
  • Process Engineering, Biotechnology, Nutrition Technology  (214)
  • 101
    Electronic Resource
    Electronic Resource
    Lysine inhibition of Saccharomyces cerevisiae: role of repressible L-lysine ε-aminotransferase (1994)
    Springer
    World journal of microbiology and biotechnology 10 (1994), S. 572-575 
    Details
    ISSN: 1573-0972
    Keywords: Growth inhibition ; L-lysine ε-aminotransferase ; nitrogen limitation ; α-oxoadipic acid ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Lysine added to grain mashes under nitrogen-limiting conditions (as in most industrial fermentations) inhibited growth of Saccharomyces cerevisiae. This inhibition was relieved by raising the assimilable nitrogen content. Lysine-induced inhibition is not mediated through accumulation of α-oxoadipic acid, an intermediate of lysine metabolism which accumulates by a back up of intermediates in de novo synthesis. Lysine degradation is regulated by the synthesis of L-lysine ε-aminotransferase, an enzyme that catalyses the first step in one of three possible routes of lysine degradation (not previously reported in S. cerevisiae). Synthesis is repressed under nitrogenlimiting conditions, but derepressed when excess assimilable nitrogen is available. Derepression results in degradation of lysine and decreases inhibitory effects on growth. The toxic compound appears to be lysine itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367670
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  • 102
    Electronic Resource
    Electronic Resource
    Crossflow filtration of yeast broth cultivated in molasses (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 1094-1101 
    Details
    ISSN: 0006-3592
    Keywords: crossflow filtration ; microfiltration ; Saccharomyces cerevisiae ; molasses ; backwashing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A broth of yeast cells cultivated in molasses was crossfiltered with a thin-channel module. The permeation flux gradually decreased at a constant cell concentration. The flux was much lower than that obtained for yeast broth cultivated in yeast extract, polypeptone, and dextrose (YPD) medium during the filtration. The flux did not depend on the membrane pore size (0.45 to 5 μm). The steady-state flux was one-twentieth that calculated for a cake filtration mode from the amount of cake per unit filtration area and the specific resistance of the cake measured in a dead-end filtration apparatus. The lower flux was due to small particles (most of which were less than 1 μm in diameter) in the molasses. The mehanism of crossflow filtration of broths of yeast cells cultivated in molasses was clarified by analysis of the change in flux with time and observations with scanning electron microscopy. At the initial stage of crossflow filtration the yeast cells and particles from the molasses were deposited on the membrane to form the molasses were deposited on the membrane to form a cake in a similar way to dead-end filtration. After the deposition of cells onto the membrane ceased, the fine particles from molasses formed a thin layer, which had higher resistance than the cake formed next to the membrane. The backwashing method was effective to increase the flux. The flux increased low when the pore size was 0.45 to 0.08 μm, but using larger pores of 3 to 5 μm it returned almost to the bases line. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431113
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  • 103
    Electronic Resource
    Electronic Resource
    Ethanol production from nonsterilized carob pod extract by free and immobilized Saccharomyces cerevisiae cells using fed-batch culture (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 189-194 
    Details
    ISSN: 0006-3592
    Keywords: ethanol ; Saccharomyces cerevisiae ; carob pod ; fed-batch culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of ethanol from carob pod extract by free and immobilized Saccharomyces cerevisiae cells in batch and fed-batch culture was investigated. Fed-batch culture proved to be a better fermentation system for the production of ethanol than batch culture. In fed-batch culture, both free and immobilized S. cerevisiae cells gave the same maximum concentration (62 g/L) of final ethanol at an initial sugar concentration of 300 g/L and F = 167 mL/h. The maximum ethanol productivity (4.4 g/L h) was obtained with both free and immobilized cells at a substrate concentration of 300 g/L and F = 334 mL/h. In repeated fed-batch culture, immobilized S. cerevisiae cells gave a higher overall ethanol concentration compared with the free cells. The immobilized S. cerevisiae cells in Ca-alginate beads retained their ability to produce ethanol for 10 days. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430302
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  • 104
    Electronic Resource
    Electronic Resource
    Physicochemical properties of the matrix proteins of three main culture vehicles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 29-37 
    Details
    ISSN: 0006-3592
    Keywords: proteins, contaminant ; Escherichia coli ; Saccharomyces cerevisiae ; mammalian cell culture ; PAGE ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The protein components of three industrial recombinant expression systems: Escherichia coli, Saccharomyces cerevisiae, and a mammalian cell culture supernatant of CHO cells were characterized in terms of their molecular weight, isoelectric point, and relative surface hydrophobicity. Identification of individual proteins was done by reference to their position in protein band profiles by polyacrylamide gel electrophoresis (PAGE) of the crude material. This permitted a rapid and facile assignment of quantitative values for these three parameters to all the major protein components in these materials. Because it is the indigenous proteins in expression systems that will form the bulk of any impurities in the product, once the values of these parameters are known for any target recombinant protein, the data obtained will enable appropriate expression systems to be chosen for minimizing amounts of potential contaminants and reducing downstream processing requirements and costs. The data will also indicate which fractionation steps (i.e., charge, size or hydrophobicity-based) are likely to be best for distinguishing between target and contaminant proteins, thus aiding and early removal of the maximum quantities of undesired protein to bring subsequent bioseparation steps down in scale and cost and up in terms of efficiency. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440106
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  • 105
    Electronic Resource
    Electronic Resource
    Real and pseudo oxygen gradients in Ca-alginate beads monitored during polarographic Po2-measurements using Pt-needle microelectrodes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 617-625 
    Details
    ISSN: 0006-3592
    Keywords: oxygen profiles ; oxygen microprobe ; Po2-microelectrode ; artifacts ; alginate beads ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Polarographic microcoaxial needle electrodes were used to measure internal profiles of dissolved oxygen tension (Po2) within single Ca-alginate beads of different diameter containing entrapped cells of Saccharomyces cerevisiae. For the investigations, single beads coming from variable growing conditions and distinct cultivation stages were fixed in a special holding device. In dependence on microbial growth steep oxygen gradients were observed. The Oxygen penetration depth at steady state lay between 50 and 100 μm. After 8 h of cultivation time, the anaerobic space within the beads (φ 2 mm; cultivation in a packed bed reactor) is beginning at ∼ 130 μm, whereas the anaerobic space within the beads (φ 2 mm) coming from the shaker flask culture is located ∼440 μm below the bead surface. Surprisingly, steep gradients were also observed, when recording profiles from cell-free Ca-alginate beads of different diameter and alginate concentrations. The steep oxygen gradients apparently had to be interpreted as pseudo-Po2-gradients. These results were borne by several effects, such as formation of artifacts and diffusion barriers in front of the electrode tip or oxygen “availability” at the tip and consumption of oxygen by the electrode itself. These phenomena could be documented by microscopic observation and photography. Thus, to obtain real Po2-profiles it is important to be exactly informed about the physical, chemical, and biological properties of the material to be investigated. Furthermore, it is necessary to apply a special stepwise puncture technique with distinct step-in/step-out movements of the electrode: e.g., unidirectional or contradirectional puncture techniques. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440508
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  • 106
    Electronic Resource
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    The use of hollow fiber cross-flow microfiltration in bioaccumulation and continuous removal of heavy metals from solution by Saccharomyces cerevisiae (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1362-1366 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; bioaccumulation ; gel immobilization ; cross-flow microfiltration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cross-flow microfiltration was shown to retain Saccharomyces cerevisiae biomass utilized for heavy metal bioaccumulation. The passage of metal-laden influent through a series of sequential bioaccumulation systems allowed for further reductions in the levels of copper, cadmium, and cobalt in the final effluent than that afforded by a single bioaccumulation process. Serial bioaccumulation systems also allowed for partial separation of metals from dual metal influents. More than one elemental metal cation could be accumulated simultaneously and in greater quantities than when a single metal was present in the effluent (Cu2+ 0.43 mmol, Cu2+ + Cd2+ 0.67 mmol, and Cu2+ + Co2+ 0.83 mmol/g yeast dry mass when the initial concentration of each of the metal species was 0.2 mmol·L-1). Co-accumulation of two different metal cations allowed higher total levels of bioaccumulation than found with a single metal. The flux rate was 2.9 × 102 L·h-2μm-2 using a polypropylene microfiltration membrane (0.1 μm pore size) at 25°C. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260441113
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  • 107
    Electronic Resource
    Electronic Resource
    The release of virus-like particles from recombinant Saccharomyces cerevisiae: Effect of freezing and thawing on homogenization and bead milling (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 736-744 
    Details
    ISSN: 0006-3592
    Keywords: disruption kinetics ; Saccharomyces cerevisiae ; virus-like particles ; recombinant cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant cells of Saccharomyces cerevisiae, expressing virus-like particles (Ty-VLPs), can be readily disrupted in a high pressure homogenizer and show identical disruption kinetics to the untransformed host strain. When the cells are freeze/thawed before disruption, they become about four times more resistant to homogenization. This effect increases with the number of freeze/thaw cycles, but is independent of the time the cells remain frozen. The freeze/thaw effect is observed with cells harvested during both the logarithmic and stationary phase of growth, and occurs with the untransformed host strain as well as the transformed one. Freeze/thawed cells are twice as resistant to disruption in the bead mill as fresh cells. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440610
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  • 108
    Electronic Resource
    Electronic Resource
    Novel protein a affinity matrix prepared from two-dimensional protein crystals (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 321-330 
    Details
    ISSN: 0006-3592
    Keywords: crystalline surface layers ; Protein A ; immobilization ; affinity matrix ; Clostridium thermohydrosulfuricum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this article, we describe a novel type of affinity matrix which was prepared by covalently binding Protein A to crystalline cell surface layers (S-layers) from the gram-positive Clostridium thermohydrosulfuricum L111-69. S-layers were used in the form of cell wall fragments, which were obtained by breaking whole cells by ultrasonification and removing the cell content and the plasma membrane. In these thimble shaped structures, revealing a size of 1 to 2 μm, the peptidoglycan-containing layer was covered on both faces with a hexagonally ordered S-layer lattice composed of identical glycoprotein subunits. After crosslinking the S-layer protein with glutaraldehyde, carboxyl groups from acidic amino acids were activated with carbodiimide and used for immobilization of Protein A. Quantitative determination confirmed that up to two Protein A molecules were bound per S-layer subunit leading to a dense monomolecular coverage of the immobilization matrix with the ligand.Affinity microparticles were capable of adsorbing lgG from solutions of purified preparations, from artificial lgG-albumin mixtures, and from serum. The amount of lgG bound to affinity microparticles corresponded to the theoretical saturation capacity. Under appropriate conditions, up to 95% of the adsorbed lgG could be eluted again. Affinity microparticles were found to have an extremely low Protein A leakage and a high stability toward mechanical forces. Because pores in the S-layer lattice revealed a size of 4 to 5 nm, immobilization of Protein A and adsorption of lgG was restricted to the outermost surface area. This excludes mass transfer problems usually encountered with affinity matrices prepared from amorphous polymers where more than 90% of the ligands are immobilized in the interior. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260430409
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  • 109
    Electronic Resource
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    Blueprint for a lipase support: Use of hydrophobic controlled-pore glasses as model systems (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 934-938 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; nonaqueous enzymology ; esterification ; Rhizomucor miehei lipase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the commercial exploitation of lipase biocatalysis to be successful, it is essential that effective supports are selected for lipase immobilization. In this study hydrophobic controlled-pore glasses have been used as model systems for the immobilization of Rhizomucor miehei lipase. The effect of pore diameter and surface chemistry on enzyme efficiency in a typical esterification reaction under essentially nonaqueous conditions has been examined. It has been found that pore diameters of at least 35 nm are needed for the lipase to be able to utilize the internal volume of the support particles in the immobilization process. Despite the small size of the substrates in the esterification reaction, even larger pores (〉100 nm) are required for the lipase efficiency to become independent of pore diameter; below 100 nm lipase activity and efficiency are markedly reduced. It has also been shown that the chemical nature of the hydrophobic surface plays an important part in catalyst design. Although lipase will adsorb readily to a wide range of hydrophobic groups, the highest catalyst activities are obtained when the glass surface is derivatized to give long alkyl chains; the presence of unsaturated derivatives gonerally leads to a reduction in activity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260431006
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  • 110
    Electronic Resource
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    Increased thermostability of Asn182 → Ala mutant Aspergillus awamori glucoamylase (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 101-105 
    Details
    ISSN: 0006-3592
    Keywords: Aspergillus awamori ; glucoamylase ; kinetic ; thermostability ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asn182 → Ala Aspergillus awamori glucoamylase expressed in Saccharomyces cerevisiae had a first-order thermodeactivation coefficient 40% that of wild-type glucoamylase at pH 4.5 between 60° and 65°C, caused by the elimination of an Asn - Gly sequence subject to deamidation and eventual chain breakage. Above 70°C, and at pHs 3.5 and 5.5, thermodeactivation coefficients of wild-type and mutant enzymes were roughly equal, because the fastest deactivation mechanism was no longer deamidation. The mutation had little effect on the enzyme's optimal pH for activity and subsite map, or on the glucose yield from starch dextrin hydrolysis. During enzyme production by yeast fermentation, highest cell densities and activities of wild-type and mutant glucoamylases were attained after a period of glucose starvation, followed by a second addition of glucose. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430113
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  • 111
    Electronic Resource
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    Long-Term continuous culture of hepatocytes in a packed-bed reactor utilizing porous resin (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 635-644 
    Details
    ISSN: 0006-3592
    Keywords: hepatocytes ; artificial liver ; long-term culture ; packed-bed reactor ; porous resin ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As part of our attempt to develop a hybrid artificial liver support system using cultured hepatocytes, we investigated the long-term metabolic function of hepatocytes incubated in a packed-bed type reactor using reticulated polyvinyl formal (PVF) resin as a supporting material. Long-term (up to 1 week) perfusion culture experiments using the packed-bed reactor (20 mm i.d.) loaded with 500 PVF resin cubes (mean pore size 250 μm, 2 × 2 × 2 mm), together with conventional monolayer culture experiments as controls, were performed in serum-free or serum-containing medium. Ammonium metabolism and urea synthesis activities were evaluated quantitatively based on reaction kinetic analyses. Initial rates of ammonium metabolism and urea-N synthesis, as well as GPT enzyme activities, were adopted as indexes of the metabolic performance of the reactor and activities of the cultured hepatocytes.When serum-free medium was used in the perfusion cultures, ammonium metabolic and urea-N synthetic rates showed significant decay with elapse of the culture period, being less than 10% of those measured on day 1. This loss of activity was more prominent in the perfusion culture than in the monolayer cultures using this medium. In contrast, when serum-containing medium was used, approximately 50% of these activities obtained on day 1 were maintained even at the end of the cultures both in the perfusion and monolayer culture experiments.We concluded that the packed-bed reactor using PVF resin enabled high-density culture of hepatocytes, and showed a satisfactory ability to maintain the metabolic function of immobilized hepatocytes for relatively long periods of up to 1 week. This type of reactor is thus considered to represent a breakthrough in overcoming the difficulties involved in the development of a hybridtype artificial liver support system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260430713
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  • 112
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    Production of lignin peroxidase by Phanerochaete chrysosporium immobilized on porous poly(styrene-divinylbenzene) carrier and its application to the degrading of 2-chlorophenol (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 79-86 
    Details
    ISSN: 0006-3592
    Keywords: lignin peroxidase ; Phanerochaete chrysosporium ; white-rot-fungus ; polymers ; immobilization ; 2-chilorophenol ; biodegradation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Porous poly(styrene-divinylbenzene) carriers, for the immobilization of white rot fungus Phanerochaete chrysosporium have been prepared by the concentrated emulsion polymerization method. The concentrated emulsion consists of a mixture of styrene and divinylbenzene containing a suitable surfactant and an initiator as the continuous phase, and water as the dispersed phase. The polymerization of the monomers of the continuous phase generated the polymer carrier with a porcus structure. The white rot fungus Phanerochaete chrysosporium has been immobilized on porous poly(styrene-divinylbenzene) carriers and used for the batch production and the repeated batch production of lignin peroxidase in shake cultures based on a carbon-limited medium containing veratryl alcohol. The best results were achieved when a spore inoculum was used for immobilization instead of 1-day-old mycelial pellets, for both the batch production and the repeated batch production. The porous poly(styrene-divinylbenzene) immobilized Phanerochaete chrysosporium and freely suspended mycelial pellets were used as biocatalysts for the degradation of 2-chilorophenol in a 2-L bioreactor. The porous poly(styrene-divinylbenzene) particle (diameter ≅ 0.2 cm) immobilized spores exhibited a much higher activity in the degradation of 2-chlorophenol than the freely suspended mycelial pellets. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440112
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  • 113
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    Diffusion of acetophenone and phenethyl alcohol in the calcium-alginate-bakers' yeast-hexane system (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1217-1227 
    Details
    ISSN: 0006-3592
    Keywords: acetophenone ; phenethyl alcohol ; Saccharomyces cerevisiae ; diffusion coefficient ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The intrabead diffusion coefficients of acetophenone and phenethyl alcohol were measured at 30°C in the triphasic immobilized yeast-water-hexane system. Saccharomyces cerevisiae cells were deactivated with hydrochloric acid and entrapped in calcium-alginate beads. Measurements of dry cell loss during deactivation, shrinkage of the beads during deactivation and the final porosity of the beads were made for various cell loadings. Final concentrations of wet cells in the beads ranged from approximately 0.25 to 0.30 g/mL. Mass transfer in the hexane phase, external to the beads, was eliminated experimentally. The estimated error of 5% to 10% in the diffusion coefficients is within the experimental error associated with the bead method. The effect of significant sampling volumes on the diffusivities was estimated theoretically and accounted for experimentally. The intrabead concentration of acetophenone and phenethyl alcohol was 150 to 800 ppm. The deactivated cells were shown to be impervious to acetophenone so that the measured diffusivities are extracellular parameters. The cell volume fraction in the beads ranged from 0.70 to 0.90, significantly higher than previously reported data. The effective diffusion coefficients conform to the random pore model. No diffusional interaction between acetophenone and phenethyl alcohol was observed. The addition of 2 vol% ethanol or methanol slightly increased the diffusivities. The thermodynamic partition coefficients were measured in the bead-free water-organic system and found to be an order of magnitude lower than the values calculated from the analysis of the diffusion data for the organic-bead system, suggesting that bead-free equilibrium data cannot be used in triphasic systems. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260441009
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  • 114
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    Immobilization of “Disguised” yeast in chemically crosslinked chitosan beads (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1083-1088 
    Details
    ISSN: 0006-3592
    Keywords: chitosan ; crosslinking ; yeast immobilization ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new simple method for the preparation of chemically crosslinked chitosan beads is presented. It consists of the dropwise addition of 2-3% (w/v) low molecular weight chitosan solution containing 2% (w/v) glyoxal in 1% (w/v) tetrasodiumdiphosphate, pH 8.0. Immobilized viable baker's yeast (Saccharomyces cerevisiae) could be obtained via gel entrapment within the new beads when means preventing their direct contact with soluble chitosan were provided, “disguising” the cells until gelation and crosslinking were completed. Such means included cell suspension in castor oil or mixing with carboxymethyl-cellulose powder. Application of these means was shown to be necessary, as cells exposed to soluble chitosan immediately lost their viability and glycolytic activity. Yeast disguised in castor oil was also protected from bead reinforcement by glutaraldehyde treatment, significantly strengthening bead stability while operating under acidic conditions. This capability was demonstrated by continuous ethanol production by chitosan entrapped yeast. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260440909
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  • 115
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    Immobilization of milk-clotting proteases (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 139-144 
    Details
    ISSN: 1573-0972
    Keywords: Cheese ; immobilization ; milk-clotting enzymes ; proteases ; rennet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Traditionally, cheese manufacturing is a batch process and current practice is to use a milk-clotting enzyme in a soluble form. Immobilization of proteases for milk coagulation has received renewed interest and potential applications have recently been reported. Use of immobilized proteases would permit renneting of milk as a continuous process. In addition, it should be possible to recover and re-use the enzyme for coagulation of further batches of milk. This review elaborates on the recent developments in the area of immobilized proteases and their application in cheese-making.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327823
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  • 116
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    Genetic recombination of homologous plasmids catalysed by cell-free extracts of topo-isomerase mutant strains of Saccharomyces cerevisiae (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 583-586 
    Details
    ISSN: 1573-0972
    Keywords: Cell-free extracts ; plasmids ; recombination ; Saccharomyces cerevisiae ; topo-isomerase mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cell-free extracts of the yeast Saccharomyces cerevisiae can be used to catalyse the recombination of bacterial plasmids in vitro. Recombination between homologous plasmids containing different mutations in the gene encoding tetracycline resistance is detectable by the appearance of tetracycline-resistance following transformation of the recombinant plasmid DNA into Escherichia coli DH5. This in vitro recombination system was used to determine the involvement of eukaryotic topo-isomerases in genetic recombination. Cell-free extracts prepared from a temperature-sensitive topo-isomerase II mutant (top2-1) of S. cerevisiae yielded tetracycline-resistant recombinants, when the recombination assays were performed at both a non-restrictive temperature (30°C) and the restrictive temperature (37°C). This result was obtained whether or not ATP was present in the recombination buffer. Extracts from a non-conditional topo-isomerase I mutant (top1-1) of S. cerevisiae yielded tetracycline-resistant recombinants, as did a temperature-sensitive double mutant (top2-1/top1-8) at the restrictive temperature. The results of this study indicate that neither topo-isomerase I nor topo-isomerase II was involved in the recombinational activity examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386299
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  • 117
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    Biosynthesis of invertase by Saccharomyces cerevisiae with sugarcane molasses as substrate (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 662-663 
    Details
    ISSN: 1573-0972
    Keywords: Biosynthesis ; invertase ; molasses ; Saccharomyces cerevisiae ; yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Biosynthesis of invertase by Saccharomyces cerevisiae 01K32 was inversely proportional to the concentration of sugarcane blackstrap molasses included in the medium. In a fermenter, an intracellular invertase activity of 440 U/g dry cells was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369576
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  • 118
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    A possible application of ale brewery strains ofSaccharomyces cerevisiae in lager beer production (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 70-72 
    Details
    ISSN: 1573-0972
    Keywords: Beer ; brewing ; non-head forming ale yeast ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The physiological characteristics of two strains of brewery ale yeasts,Saccharomyces cerevisiae, with sedimentation abilities, were investigated to see if the strains were suitable for lager beer production. Compared with typical industrial ale strains ofS. cerevisiae and lager strains ofS. uvarum (nowS. cerevisiae), the investigated strains differ in fermentation dynamics, as well as in biological properties. The differences, however, particularly between the two strains and the lager brewing yeasts, were not significant.
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    URL: http://dx.doi.org/10.1007/BF00656520
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    Influence of culture density, pH, organic acids and divalent cations on the removal of nutrients and metals by immobilized Anabaena doliolum and Chlorella vulgaris (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 196-201 
    Details
    ISSN: 1573-0972
    Keywords: Anabaena doliolum ; calcium ; Chlorella vulgaris ; heavy metals ; immobilization ; magnesium ; organic acids ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The potential of alginate-immobilized Anabaena doliolum and Chlorella vulgaris was assessed for removal of nutrients (NO inf3 sup- and NH inf4 sup+ ) and metals (Cr2O inf7 sup2- and Ni2+) at different biomass concentrations (0.05, 0.1, 0.25, 0.49 and 1.22 g dry wt l-1) and pH values (4 to 10). Though uptake of all these substances was higher in concentrated algal beads (0.25, 0.49 and 1.22 g dry wt l-1), their rate of uptake was significantly (P〈0.001) lower than that of low (0.05 g dry wt l-1) cell density beads. For A. doliolum, there was no significant difference in uptake rates for beads having densities of 0.05 and 0.1 g dry wt l-1. Chlorella vulgaris, however, showed maximum efficiency at 0.1 g dry wt l-1. Uptake of both the nutrients and the metals was maximal at pH 7 followed by pH 8, 6, 9, 10, 5 and 4. Of the different substances (organic acids and divalent cations) used, humic acid was most efficient in decreasing metal uptake. Mg2+ was, however, more efficient than Ca2+ in decreasing Ni2+ uptake. Immobilized algae with a cell density of 0.1 g dry wt l-1 were the most efficient for nutrient and metal removal at pH 6 to 8.
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    URL: http://dx.doi.org/10.1007/BF00327836
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    Properties of Aspergillus japonicus β-fructofuranosidase immobilized on porous silica (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 216-220 
    Details
    ISSN: 1573-0972
    Keywords: Aspergillus ; β-fructofuranosidase ; fructo-oligosaccharide ; immobilization ; porous silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract β-Fructofuranosidase from Aspergillus japonicus MU-2, which produces fructo-oligosaccharides (1-kestose: O-β-D-fructofuranosyl-(2 → 1)-β-D-fructofuranosyl α-D-glucopyranoside); and nystose: O-β-D-fructofuranosyl-(2 → 1)-β-D-fructofuranosyl-(2 → 1)-β-D-fructofuranosyl α-D-glucopyranoside) from sucrose, was immobilized, covalently with glutaraldehyde onto alkylamine porous silica, at high efficiency (64%). Optimum pore diameter of porous silica for immobilization of the enzyme was 91.7 nm. After immobilization, the enzyme's stabilities to temperature, metal ions and proteolysis were improved, while its optimum pH and temperature were unchanged. The highest efficiency of continuous production of fructo-oligosaccharides (more than 60%), using a column packed with the immobilized enzyme, was obtained at 40% to 50% (w/v) sucrose. The half-life of the column during long-term continuous operation at 55°C was 29 days.
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    Immobilization of Zymomonas mobilis 2716, for the protection of cellular activity (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 366-371 
    Details
    ISSN: 1573-0972
    Keywords: Alginate ; freeze-substitution ; immobilization ; Zymomonas mobilis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Alginate-immobilized Zymomonas mobilis cells produced 17.8% (v/v) ethanol in less than 24 h, with an ethanol yield of 97%, compared with 88% for free cells, using a fed-batch cultivation technique. The substrate, glucose, was added intermittently in powder form to foster nucleation of the CO2 formed. Repeated-batch cultivation led to complete utilization of approximately 200 g glucose/l in 7.5 h with a 98% conversion efficiency to ethanol. Free cells used the glucose less efficiently (conversion efficiency of 78%), and even after 100 h the glucose was not fully consumed. Freeze-substitution electron microscopy studies showed that immobilized cells generally displayed lesser blebbing and membrane disruption than free cells. These studies further suggest that membrane blebbing may be due to an effect of high initial glucose levels, and not due to the accumulation of end-products ethanol and CO2.
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    URL: http://dx.doi.org/10.1007/BF00383082
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    Degradation of nitriles and amides by the immobilized cells of Pseudomonas putida (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 483-486 
    Details
    ISSN: 1573-0972
    Keywords: Acetonitrile ; amides ; biodegradation ; immobilization ; nitriles ; Pseudomonas putida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pseudomonas putida, capable of utilizing acetonitrile as a sole source of C and N, was immobilized in calcium alginate and the rates of degradation of nitriles, including acetonitrile, and their respective amides were studied. All the organic nitriles and amides tested were converted into NH3 and CO2.
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    Potential applications of viable, immobilized fungal cell systems (1993)
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 495-502 
    Details
    ISSN: 1573-0972
    Keywords: Fungi ; immobilization ; potential applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Immobilized cell technology attracts considerable attention because of the many advantages it offers over conventional suspended-cell fermentations. Important advances continue to be made in the potential use of immobilized cells as biocatalysts. This review is mainly devoted to the analysis of recent literature on the applications of immobilized fungal cell systems, ranging from the production or transformation of useful compounds (e.g. organic acids, enzymes, antibiotics, steroids, etc.) to wastewater treatment. The problems and future industrial applications are also discussed.
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    URL: http://dx.doi.org/10.1007/BF00386282
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    Factors affecting the performance of crossflow filtration of yeast cell suspension (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 617-624 
    Details
    ISSN: 0006-3592
    Keywords: crossflow filtration ; microfiltration ; baker's yeast ; Saccharomyces cerevisiae ; molasses ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Factors affecting the performance of crossflow filtration were investigated with a thin-channel module and yeast cells. In crossflow filtration of Saccharomyces cerevisiae cells cultivated with YPD medium (Yeast extract, polypeptone, and dextrose) and suspended in saline, a steady state was attained within several minutes when the cell concentration was low and the circulation flow rate was high. The steady-state flux and the change in flux during the initial unsteady state were explained well by conventional filtration theory, with the amount of cake deposited and the mean specific resistance to the cake measured in a dead-end filtration apparatus used in calculation. When the circulation flow rate was lower than a critical value, a part of the channel of the crossflow filtration module was plugged with cell cake, and thus the steady-state flux was low. In crossflow filtration of suspensions of commercially available baker's yeast, the flux gradually decreased, and the flux after 8 h of filtration was lower than the value calculated by filtration theory. Fine particles contaminating the baker's yeast was responsible for the decrease. A similar phenomenon was responsible for the decrease. A similar phenomenon was observed in crossflow filtration of a broth of S. cerevisiae cells cultivated in molasses medium, which also contains such particles, had no effect of the permeation flux during crossflow filtration. © 1993 John Wiley & Sons, Inc.
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    Bioconversion of lactose/whey to fructose diphosphate with recombinant saccharomyces cerevisiae cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 398-400 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; bioconversion ; fructose diphosphate production ; whey ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Genetically engineered Saccharomyces cerevisiae strains that express Escherichia coli β-galactosidase gene are able to bioconvert lactose or whey into fructose-1,6-diphosphate (FDP). High FDP yields from whey were obtained with an appropriate ratio between cell concentration and inorganic phosphate. The biomass of transformed cells can be obtained from different carbon sources, according to the expression vector bearing the lacZ gene. We showed that whey can be used as the carbon source for S. cerevisiae growth and as the substrate for bioconversion to fructose diphosphate. © 1993 John Wiley & Sons, Inc.
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    Immobilization of enzyme onto cellulose-titanium oxide composite fiber (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 394-397 
    Details
    ISSN: 0006-3592
    Keywords: cellulose ; immobilization ; fiber ; titanium oxide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fibers of a cellulose-TiO2 composite were prepared by the reaction of cellulose with titanium iso-propoxide. Enzymes were immobilized on the fibers easily and simply under mild conditions. The fibers were stable in common solvents, high ionic solutions, and over a wide range of pH values 3-10. © 1993 John Wiley & Sons, Inc.
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    Enhancement of cloned gene product synthesis via autoselection in recombinant Saccharomyces cerevisiae (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 801-810 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; autoselection ; plasmid stability ; cloned gene expression ; medium enrichment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Saccharomyces cerevisiae autoselection strains with mutations in the ura3, fur1, and urid-k genes have been obtained through a sequential isolation procedure. This autoselection system is an extension of one described by Loison et al. The mutations effectively block both the pyrimidine biosynthetic and salvage pathways and in combination are lethal to the host. Therefore, a plasmidencoded URA3 gene is essential for cell viability regardless of the growth conditions, and complex (traditionally nonselective) media can be employed without the risk of plasmid loss. The effects of medium enrichment on growth and cloned gene product synthesis were examined in batch culture for two autoselection strains. The plasmid gene product β-galactosidase was under the control of the yeast GAL1 promoter, and two methods of induction were employed; one strain was induced via temperature shift while the other was induced by galactose addition. Three nutrient media were investigated: a lean selective medium (SD), a richer semidefined medium (SDC), and a rich complex medium (YPD). The results demonstrated the improvements in cloned gene productivity possible when the growth medium is enriched, with up to 10-fold increases in β-galactosidase productivity observed. Plasmid instability and mutation reversion were not problems for the autoselection strains, even in uracil-containing medium. Short-term plasmid stabilities were approximately 90% in all three media tested. During continuous culture of the autoselection temperature-sensitive strain, long-term plasmid stability was excellent and β-galactosidase expression remained high after more than 25 residence times under inducing conditions. In contrast, both β-galactosidase specific activity and plasmid stability decreased linearly with time for an analogous nonautoselection strain. The introduced fur1 and uridk mutations were very stable; after more than 50 generations of growth in complex medium, stability values of 99-100% were measured. © 1993 Wiley & Sons, Inc.
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    Morphological characterization of yeast by image analysis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1352-1359 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; image analysis ; electronic particle counter ; viability test ; alcoholic fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semiautomatic image analysis method, with minimal operator intervention, has been developed to characterize the morphology of yeast cells under the assumption that they have an ellipsoidic shape. The cells are observed by optical microscopy and the surface and the minor and major half-axes of the projection of the ellipsoid on the image plane are determined. Using this method, yeast size distributions and population kinetics (single and budding cells, cell clusters) are determined during alcoholic fermentations. Combination of image analysis with a methylene blue viability test is examined but the staining procedure induces a change in the size of the cells. © 1993 John Wiley & Sons, Inc.
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    Application of gravitational sedimentation to efficient cellular recycling in continuous alcoholic fermentation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 361-369 
    Details
    ISSN: 0006-3592
    Keywords: gravitational sedimentation ; sedimentation ; fermentation ; continuous ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model for the sedimentation velocity in an inclined parallel plate sedimenter is proposed. The parameters of the alcoholic fermentation broth (cell density of Saccharomyces cerevisiae, density of the fermentation medium, viscosity of the broth at various alcohol and biomass contents) were determined experimentally. The sedimentation velocities were predicted under the various operational conditions and parameters, both of the broth (the alcohol concentration and cell content) and the sedimenter prototype (length, distance between the plates, and slope). The proposed model for the sedimentation velocity presented a good correlation with the experimental results of continuous sedimentation. These sedimenter prototypes were assembled and tested for efficiency of separation of yeast cell under conditions considered for interest for continuous alcoholic fermentation. A selective filter for the overflow composed of calcium alginate gel improved operation. A high operational stability, high separation efficiency (over 98%), and adequate settler residence times (about 20 min) were attained. The operational results permitted the operation of continuous alcoholic fermentation with cellular recycling effected exclusively by gravitational sedimentation, this characterizing a process of enormous industrial interest because of the operational simplicity and low operational and maintenance costs. © 1993 John Wiley & Sons, Inc.
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    Regeneration of NADH in a bioreactor using yeast cells immobilized in alginate fiber: I. Method and effect of reactor variables (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 43-49 
    Details
    ISSN: 0006-3592
    Keywords: calcium alginate reactor ; NADH regeneration ; Saccharomyces cerevisiae ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Saccharomyces cerevisiae cells immobilized in a calcium alginate fiber reactor were used as a source of alcohol dehydrogenase for the NAD+-to-NADH reaction. The reaction was catalyzed by enzyme in cells on the surface of the fiber. Internal diffusional effects were present. The enzyme cell concentration was optimized by harvesting cells finally grown under anaerobic conditions. The results were expressed as an apparent reaction rate constant that was independent of NAD+ and excess ethanol concentration, was slightly affected by flow rate above a minimum value, and increased with immobilized cell concentration in the fiber. The reaction was complete after 6 to 7 h under optimal conditions of 36°C and 9.5 pH. The latter was 0.5 pH units above the free enzyme optimum, indicating that microenvironmental effects were in evidence. © 1993 John Wiley & Sons, Inc.
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    Improved protein synthesis and secretion through medium enrichment in a stable recombinant yeast strain (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 95-102 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; secretion ; MFα1 ; autoselection ; plasmid stability ; medium enrichment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two Saccharomyces cerevisiae strains were employed to investigate the effects of medium enrichment on the expression and secretion of a recombinant protein. One was a stable autoselection strain with mutations in the ura3, fur1, and urid-k genes. The combination of these three mutations blocks both the pyrimidine nucleotide biosynthetic and salvage pathways and is lethal to the cells. Retention of the plasmid, which carries a URA3 gene, was essential for cell viability. Therefore, all media were selective, allowing cultivation of the strain in complex medium. The second strain was a nonautoselection (control) strain and is isogenic to the first except for the fur1 and urid-k mutations. The plasmid utilized contains the yeast invertase gene under the control of the MFα1 promoter and leader sequence. The expression and secretion of invertase for the autoselection strain were examined in batch culture for three media: a minimal medium (SD), a semidefined medium (SDC), and a rich complex medium (YPD). Biomass yields and invertase productivity (volumetric activity) increased with the complexity of the medium; total invertase volumetric activity in YPD was 100% higher than in SDC and 180% higher than in SD. Specific activity, however, was lowest in the SDC medium. Secretion efficiency was extremely high in all three media; for the majority of the culture, 80-90% of the invertase was secreted into the periplasmic space and/or culture medium. A glucose pulse at the end of batch culture in YPD facilitated the transport of residual cytoplasmic invertase. For the nonautoselection strain, invertase productivity did not improve as the medium was enriched from SDC to YPD, and plasmid stability in the complex YPD medium dropped from 54% to 34% during one batch fermentation. During long-term sequential batch culture in YPD, invertase activity decreased by 90% and the plasmid-containing fraction dropped from 56% to 8.8% over 44 generations of growth. The expression level for the autoselection strain, however, remained high and constant over this time period, and no reversion at the fur1 or urid-k locus was observed. © 1993 John Wiley & Sons, Inc.
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    Comparison of glucose fermentation by suspended and gel-entrapped yeast cells: An in vivo nuclear magnetic resonance study (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 647-653 
    Details
    ISSN: 0006-3592
    Keywords: yeast ; continuous-flow 31P NMR ; intracellular pH ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phosphorus-31 nuclear magnetic resonance (31P NMR) was used to compare the anaerobic metabolism of glucose by suspended and gel-entrapped Saccharomyces bayanus cells. The fermentation of glucose was carried out in a reaction system with continuous circulation through the NMR sample tube. The intracellular pH and the levels of some phosphorylated compounds were the levels of some phosphorylated compounds were noninvasively monitored by 31P NMR while glucose, fermentation products, and biomass were determined by analytic techniques comparisons showed that no significant differences are observed in the relative concentrations in the spectra, but distinct profiles for the variation of both intracellular and extracellular pH are found. The internal pH of immobilized cells is maintained at a constant value throughout the fermentation as opposed to freely suspended cells for which a steady decrease in the internal pH occurs. A faster and stronger acidification is also observed in the external medium of the assays with suspended cells. Furthermore, higher yields for ethanol and biomass production and lower yields of fermentation by-products are obtained with immobilized cells. It is concluded that the higher intracellular pH achieved in the presence of the gel matrix had a regulatory effect on the metabolism which favored the ethanol production pathway. © 1993 John Wiley & Sons, Inc.
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    Cadmium biosorption by Saccharomyces cerevisiae (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 826-829 
    Details
    ISSN: 0006-3592
    Keywords: biosorption ; biosorbent ; Saccharomyces cerevisiae ; cadmium biosorption ; metal uptake ; brewer's yeasts ; baker's yeasts ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium-bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal-sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min. © 1993 Wiley & Sons, Inc.
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    The adsorptive immobilization of phospholipids D mediated by calcium ions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 833-836 
    Details
    ISSN: 0006-3592
    Keywords: phospholipase D ; adsorptive immobilization ; calcium ; stabilization ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization of phospholipase D from cabbage was studied with the aim of stabilizing the enzyme for its use in synthesis of phospholipids. It was shown that phospholipase D can be immobilized by adsorption to polymeric carriers containing long chain anchor groups such as octadecyl, octyl, or other alkyl residues. Starting from the crude enzyme, phospholipase D activity is preferentially bound (up to 100%) in competition with contaminating proteins. A prerequisite of high binding rates is the presence of calcium ions, which play a mediating role in the adsorption process. The maximum activity of the carrier-enzyme complexes depends upon the calcium concentration in the immobilization process and the carrier material (≥10mM CaCl2 with octadecyl-Si40, ≥40 mM CaCl2 with octyl-sepharose and butyl-fractogel). Immobilization of phospholipase D to octyl-sepharose was shown to result in a distinctly increased storage stability and an enlarged pH-optimum range for the catalytic activity. Operational stability of different phospholipase D-carrier complexes was compared. © 1993 Wiley & Sons, Inc.
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    A bioassay of thyrotrophin by photografted mammalian cells onto polymeric supportsPart 28 of the series “Photosynthetic Membranes.” (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 255-259 
    Details
    ISSN: 0006-3592
    Keywords: thyroid cells ; immobilization ; photografting ; photocatalyst ; thryrotrophin bioassay ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Viable and functionally responsive human thyroid follicular cells, suspended in a commercial polyester acrylate diluted with tripropyleneglycol diacrylate, photoinitiated, and photocatalyzed with a proprietary photocatalytic system based on a synergic mixture of vanadium (V) t-butoxide and i-propoxide, have been immobilized as monolayers onto polystyrene plates. Bioassay of thyrotrophin in immobilized cell cultures yielded, by log-log plot of the dose-response curve, a slope (0.92 ± 0.02) in close agreement with that (0.91) reported for cells immobilized by physical adsorption. The decisive role of photocatalyst in the photografting procedure has also been shown experimentally. A mechanism is suggested by which cells are anchored, rapidly and with stable chemical bonds, onto one of the two acrylate functions of the monomer-prepolymer mixture, the other one being simultaneously responsible for photochemical grafting onto the support. © 1993 John Wiley & Sons, Inc.
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    Analytical effectiveness calculations concerning the degradation of an inhibitive substrate by a steady-state biofilm (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 267-278 
    Details
    ISSN: 0006-3592
    Keywords: biocatalyst ; immobilization ; analytical effectiveness factor ; substrate inhibition ; phenol degradation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A reaction engineering model for the degradation of an inhibitory substrate by a steady-state biofilm is presented. The model describes both the metabolic rate controlling behavior of this substrate in the biofilm and the effect of diffusion limitation caused by an arbitrary substrate on the active biofilm thickness. An analytical expression for the biocatalyst effectiveness factor is presented on the basis of Pirt kinetics for cell maintenance, first order substrate inhibition kinetics, and zero order substrate consumption kinetics. The proposed expression for the biocatalyst effectiveness factor is much more convenient to incorporate into a macroreactor model than the numerical alternatives. Simple criteria are presented to check the applicability of the model in case of true Monod kinetics. The analytical solution is expected to be particularly applicable to processes where a low soluble organic substrate controls the biomass growth, a situation which is often met in wastewater purification processes of industrial importance. The degradation of phenol by Pseudomonas sp. is treated as an example. © 1993 John Wiley & Sons, Inc.
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    Stability of antibody productivity is improved when hybridoma cells are entrapped in calcium alginate beads (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1131-1135 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; instability ; immobilization ; monoclonal antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Loss of monoclonal antibody (MAb) productivity in long-term, free-suspended cell culture is often attributed to the appearance of a nonproducing population of hybridoma cell (NP) in the culture which has a growth advantage over the producing population (P). However, when an NP appears in long-term culture of entrapped cells, it may not be able to take over the whole culture in a short period of time due to the limited growth of the entrapped cells. In order to examine the hypothesis that entrapped cells can have improved stability of MAb productivity due to limited cell growth, free-suspended cell culture and calcium alginate-entrapped cell culture with inocula consisting of a P and an NP were compared with regard to stability of MAb productivity in a repeated fed-batch culture. In free-suspended cell culture, the NP appeared to take over the whole culture within three batches, and thereby MAb production completely disappeared. In entrapped cell culture, an NP appeared to outgrow the P rapidly only during an exponential growth phase, resulting in a significant decrease in specific MAb productivity, qMAb, from 11.58 μg/106 cell/day to 2.76 μg/106 cell/day. However, when the cell growth was limited in entrapped cell culture, the NP no longer outgrew the P rapidly, as indicated by the stable value of qMAb. In addition, when the cells recovered from the alginate beads by citrate buffer treatment were subcultured in free-suspended cell culture, MAb production rapidly deteriorated and completely disappeared within two batches. Thus, the P present at a small fraction of viable cell concentration in the beginning of the free-suspended cell culture, which were previously entrapped in alginate beads, seemed to be outgrown rapidly by the NP. Taken together, the results obtained from these experiments support the hypothesis that the limited cell growth in entrapped cell culture, which keeps an NP from taking over the whole culture, is responsible, in part, for the improved stability of MAb productivity. © 1993 John Wiley & Sons, Inc.
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    Modeling and optimization of cloned invertase expression in Saccharomyces cerevisiae (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 1066-1074 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; SUC2 ; mathematical model ; conjugate gradient optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The aim of this study is to determine the medium feeding strategy to maximize the invertase productivity of recombinant Saccharomyces Cerevisiae using a fed-batch mode of operation. The yeast contains the plasmid, pRB58, which contains the yeast SUC2 gene, coding for the enzyme invertase. The expression of this gene is repressed at high glucose levels. A Goal-oriented model is development to describe the kinetics of fed-batch fermentations. This simple model could quantitatively describe previous experimental results. A conjugate gradient algorithm is then used, in conjunction gradient algorithm is then used, in conjunction with this mathematical model, to compute the optimum feed rate for maximization of invertase productivity. The optimal feeding procedure results in an initial high cell growth phase followed by a high invertase production phase. © 1993 Wiley & Sons, Inc.
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    Immobilization of lipase for effective interesterification of fats and oils in organic solvent (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 204-210 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; interesterification ; cocoa butter equivalent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to investigate quantitatively the interesterification reaction, triolein and stearic acid were used as substrates and eight commercially available lipases were tested for their suitability for the reaction. Three fungal lipase preparations were found to be suitable. The hydrolytic activity of the commercial lipases was tested with olive oil, and it 2was noted that there was no correlation between their hydrolytic and interesterification activities. Among the lipases tested, Mucor miehei lipase was chosen for further study because of it high protein content and its relatively high hydrolytic and interesterification activities, both of which are required for effective interesterification. The effect of water activity of the interesterification reaction was investigated. interesterification activity was shown to be maximum at the water activity of 0.25. As the water activity of the lipase increased, hydrolysis of triglyceride was accelerated. At zero water activity, high conversion was achieved, although interesterification activity was relatively lower than that at the water activity of 0.25. A new and simple immobilization method was developed in order to render hydrophobicity to the lipase and hence to improve the interesterification activity of the lipase. The lipase was immobilized covalently with glutaraldehyde or with six alkyl chains as spacers onto Florisil (magnesium silicate, a inorganic matrix). Interesterification activity of the immobilized lipase with the hydrophobic spacers were increased against that of re lipase. The increase of activity was up to 8-fold that of the original activity of free lipase when the spacer was 7-aminoheptanoic acids. Relatively high stability of the immobilized lipase was shown in a continuous packed bed column reactor with a half-life of 97 days. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260410206
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    Improved activity retention of enzymes deposited on solid supports (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 171-178 
    Details
    ISSN: 0006-3592
    Keywords: enzyme stabilization ; additive ; immobilization ; support material ; organic media ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzymes deposited on solid support usually show good stability when operated in organic solvents. Decreased stability of the enzyme preparations was noticed when low enzyme loadings were used (e.g., with Celite as support; less than 1 mg enzyme/g). It was possible to avoid the activity loss by the addition of an additive which protects the enzyme during the immobilization. Proteins (such as albumin, gelatin, and casein) and poly(ethylene glycol) were effective additives whereas amino acids, monomeric carbohydrates, and polysaccharides had no effect. The amount of additive needed for stabilization was shown to depend on the structure of the support, more additive being required for a support with high porosity. The stabilizing effect was investigated in a series of glyceryl-controlled-pore glass (CPG) with varying specific surface areas (9.5-180 m2/g). The minimum addition of albumin, giving full stabilization, on the different supports correlated to a monolayer coverage of the surface, approximately 2-3 mg protein/m2. The effect of the additive was less pronounced when increasing amounts of enzyme were immobilized (5-40 mg enzyme/g Celite). The effect of the additives was studied using mandelonitrile lyase, but α-chymotrypsin and lipase P were also shown to be stabilized. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260410202
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    Removal of phenols from wastewater by soluble and immobilized tyrosinase (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 854-858 
    Details
    ISSN: 0006-3592
    Keywords: phenol ; tyrosinase ; immobilization ; chitosan ; immobilized enzyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An enzymatic method for removal of phenols from industrial wastewater was investigated. Phenols in an aqueous solution were removed after treatment with mushroom tyrosinase. The reduction order of substituted phenols is catechol 〉 p-cresol 〉 p-chlorophenol 〉 phenol 〉 p-methoxyphenol. In the treatment of tyrosinase alone, no precipitate was formed but a color change from colorless to dark-brown was observed. The colored products were removed by chitin and chitosan which are available abundantly as shellfish waste. In addition, the reduction rate of phenols was observed to be accelerated in the presence of chitosan. Tyrosinase, immobilized by using amino groups in the enzyme on cation exchange resins, can be used repeatedly. By treatment with immobilized tyrosinase, 100% of phenol was removed after 2 h, and the activity was reduced very little even after 10 repeat treatments. © 1993 John Wiley & Sons, Inc.
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    Whole cell yeast biotransformations in two-phase systems: Effect of solvent on product formation and cell structure (1992)
    Springer
    Journal of industrial microbiology and biotechnology 10 (1992), S. 169-177 
    Details
    ISSN: 1476-5535
    Keywords: l-Phenylacetyl carbinol ; Biotransformations ; Two-phase systems ; Whole cells ; Saccharomyces cerevisiae ; Cell structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Biotransformation of benzaldehyde and pyruvate to (R)-phenylacetyl carbinol bySaccharomyces cerevisiae was investigated in two-phase aqueous-organic reaction media. With hexane as organic solvent, maximum biotransformation activity was observed with a moisture content of 10%. Of the organic solvents tested, highest biotransformation activities were observed with hexane and hexadecane, and lowest activities occurred with chloroform and toluene. Biocatalyst samples from biphasic media containing hexane, decane and toluene manifested no apparent cell structural damage when examined using scanning electron microscopy. In contrast, cellular biocatalyst recovered from two-phase systems containing chloroform, butylacetate and ethylacetate exhibited damage in the form of cell puncturing after different incubation periods. Phospholipids were detected in reaction media from biocatalytic systems which exhibited cell damage in electron micrographs. Phospholipid release was much lower in the two-phase systems containing toluene or hexane or in 100% aqueous biocatalytic system.
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    Influence of the curing of the killer phenotype inSaccharomyces cerevisiae wine strains on their fermentative behaviour (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 147-150 
    Details
    ISSN: 1573-0972
    Keywords: Curing ; fermentative behaviour ; killer ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Fermentative behaviour and cell growth have been studied in grape juice inoculated either with two killerSaccharomyces cerevisiae wild strains or with their Acridine Orange-cured isogenic counterparts. The number of viable cells/ml at the beginning of the fermentation, as well as during exponential growth, were higher in grape juices inoculated with the cured strains. The CO2 production, fermentative rate and ethanol and acetic acid production were also higher in the cured strains, particularly during the stage of active fermentation. These differences, however, were minimal at the end of the fermentations.
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    Nystatin and killer toxin sensitivity of free and immobilizedSaccharomyces cerevisiae (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 192-195 
    Details
    ISSN: 1573-0972
    Keywords: Covalent linkage ; immobilization ; killer toxin ; nystatin ; Phospholipids ; Signal transduction ; sterols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The inhibitory effect of nystatin and killer toxin on the growth of free and covalently-immobilizedSaccharomyces cerevisiae cells was studied. The resistance of immobilized cells to both agents was accompanied by increased amounts of phospholipids and sterols. The possible relationship between these changes in the membrane composition and the transduction of a signal across the cytoplasmic membrane is discussed.
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    Production of higher alcohols, ethyl acetate, acetaldehyde and other compounds by 14Saccharomyces cerevisiae wine strains isolated from the same region (Salnés, N.W. Spain) (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 539-541 
    Details
    ISSN: 1573-0972
    Keywords: Aroma ; compound ; Saccharomyces cerevisiae ; wine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Fourteen strains of the yeastSaccharomyces cerevisiae were isolated from three wineries in the Salnés wine region (N.W. Spain) at the three different periods of the natural fermentation. Each wild yeast was screened for production of acetaldehyde, ethyl acetate, isobutanol,n-propanol, amylic alcohol and other important enological compounds during laboratory scale fermentations of grape juice. After 25 days at 20°C, the analytical results evidenced variations in the production of acetaldehyde (from 13.1 to 24.3 mg/l), isobutanol (from 27.7 to 51.1 mg/l), amyl alcohols (from 111 to 183 mg/l) and ethyl acetate (from 19.3 to 43.7 mg/l). Although isolated from the same wine region, differences in the wine composition were observed depending on the particular yeast strain used for the vinification experiments.
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    Stimulative effect of non-parenchymal liver cells on ability of tyrosine aminotransferase induction in hepatocytes (1992)
    Springer
    Cytotechnology 10 (1992), S. 25-31 
    Details
    ISSN: 1573-0778
    Keywords: bioartificial liver ; calcium alginate ; hepatocytes ; immobilization ; non-parenchymal liver cell ; tyrosine aminotransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Hepatocytes and non-parenchymal liver cells were isolated from adult rat liver and co-cultured for 48 hours as a monolayer on polystyrene culture dishes. The ability of tyrosine aminotransferase (TAT) induction in hepatocytes was examined in the presence of dexamethasone and dibutyryl cAMP. Non-parenchymal cells greatly enhance the ability of TAT induction of hepatocytes. A soluble factor with molecular weight of more than 10,000 is responsible for this enhancement, because conditioned medium prepared from non-parenchymal cells is also stimulatory. Non-parenchymal cells restored the ability in hepatocytes damaged with the addition of D-galactosamine. Conditioned medium prepared from non-parenchymal cells treated with D-galactosamine had higher activity of enhancement than the medium from normal cells. The soluble factor might be released in response to some signal of injury. Hepatocytes and non-parenchymal cells were immobilized within Ca-alginate, and although immobilized hepatocytes rapidly lost the ability to induce TAT, hepatocytes co-immobilized with non-parenchymal cells maintained the ability during 4 days of culture. These results indicated that non-parenchymal liver cells, as well as hepatocytes, could be used to construct a bioartificial liver support system.
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    α-Glucosidase synthesis in batch and continuous culture ofSaccharomyces cerevisiae (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 42-44 
    Details
    ISSN: 1573-0972
    Keywords: Saccharomyces cerevisiae ; maltose induction ; catabolite repression ; chemostat ; α-glucosidase ; permease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Glucose prevented maltose utilization in batch culture ofSaccharomyces cerevisiae whereas in a mixed carbohydrate-limited system, maltose and glucose were consumed simultaneously. The specific activity of α-glucosidase depended on the dilution rate as well as the proportion of maltose in the mixture. The chemostat provides a way of reaching the low residual concentrations of glucose in the broth that are necessary to release catabolite repression and permit maltose induction of α-glucosidase.
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    Phenotypic character of the lipid hydroperoxide-resistant mutant: Positive relationship between flocculation and resistance against lipid hydroperoxide inSaccharomyces cerevisiae (1992)
    Springer
    World journal of microbiology and biotechnology 8 (1992), S. 296-300 
    Details
    ISSN: 1573-0972
    Keywords: Flocculation ; linoleic acid hydroperoxide ; lipid hydroperoxide ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A lipid hydroperoxide-resistant mutant was isolated from a strain ofSaccharomyces cerevisiae. The mutant was resistant to 1.5mm tert-butylhydroperoxide and 1.0mm linoleic acid hydroperoxide. It flocculated in a Ca2+-dependent manner and the resistance against lipid hydroperoxide was suppressed by mannose, which also inhibited flocculation. A positive relationship between the acquirement of, the flocculent phenotype and resistance against lipid hydroperoxide is suggested. A protein with a molecular weight of 33 kDa was found on the surface of the mutant cell.
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    Surface immobilization of anchorage-dependent mammalian cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 697-706 
    Details
    ISSN: 0006-3592
    Keywords: anchorage-dependent mammalian cells ; immobilization ; fibers ; bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anchorage-dependent HeLa cells were successfully cultured on two fibrous materials (A07 and R100) with porosities of 75-125 and 40 μm, void fractions of 92% and 81%, and fiber diameters of 7.6 and 10.2 μm, respectively, in 100-mL spinner flasks and 2-L stirred tank bioreactors. The matrix was formed into a fixed vertical spiral configuration. All cultures displayed rapid (≤2-3 h) attachment of inoculated cells (≥95%) to the matrix, uniform coverage of the immobilizing area with viable cells, and no significant amount of cell debris in the medium. Spinner flask cultures indicated that the denser material R100 showed better results in terms of final cell density. The growth of HeLa cells on material R100 in both culture systems was similar to that observed in tissue culture dishes (specific growth rate ∼0.03-0.04 h-1, maximum cell density of 8 × 106-9 × 106 cells · mL-1, and yields of 0.4 × 108 cells · mM-1 on glucose and 2 × 108-3 × 108 cells · mM-1 on glutamine). Scale-up of this culture technique in a 2-L bioreactor under perfusion with pH and dissolved oxygen (DO) control yielded cell densities of up to 1.6 × 106 cells · mL-1. Two other anchorage-dependent mammalian cells (ADC) known to be cultured with difficulty in roller bottles or with micro carriers were easily grown on material R100 in spinner flasks. The performance of this culture technique was compared to other ADC culture systems.
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    Inner mitochondrial membranes bound to concanavalin A-sepharose display succinate dehydrogenase, ATPase, and cytochrome oxidase activity (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1080-1085 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; mitochondrial membranes ; cytochrome oxidase ; ATPase, concanavalin A-Sepharose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fraction (15-20% of the total protein) of a preparation of bovine submitochondrial particles (SMPs) binds to concanavalin A-sepharose. The bound membranes displayed succinate dehydrogenase, cytochrome oxidase, and ATPase activity, which, as in SMPs, were inhibited by malonate, cyanide, and oligomycin, respectively. These results indicate that the bound membranes are inner mitochondrial membranes and that they contain a glycoprotein which was recognized by concanavalin A. It was possible to repeatedly perform the three enzyme assays, one after the other, in the same gel with the bound membranes. Long-term stability tests (22 days) showed that cytochrome oxidase was much more stable in the membranes bound to the gel than in SMPs, while the ATPase activity decayed at a similar rate in the two conditions. Thus, inner mitochondrial membranes bound to ConA-Sepharose appear to be a potentially interesting model for the study of immobilized multienzymatic complexes.
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    Effect of feed zone in fed-batch fermentations of Saccharomyces cerevisiae (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 235-246 
    Details
    ISSN: 0006-3592
    Keywords: Fed-batch fermentation ; concentration fluctuations ; mixing effects ; Saccharomyces cerevisiae ; circulation time distribution ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In production-scale, fed-batch fermentations, feed is often added to a single point at the top of the fermentor, which, combined with poor mixing, results in formation of a “feed zone” rich in nutrients. Frequent exposure of the culture to high concentrations of nutrients in the feed zone for sufficient duration can produce unexpected effects on its performance. The effect of the feed zone was evaluated by conducting aerobic fed-batch fermentations of Saccharomyces cerevisiae with both complex and defined media. The broth was recirculated between a recycle loop and a bench-scale fermentor, and feed was intermittently added into the recycle loop to simulate the circulation of cells through the feed zone. Experiments were carried out for a range of residence times in the recycle loop from 0.5 to 12 min. Biomass yields from the complex-media fermentations were not affected by exposure to high nutrient levels in the recycle loop for residence times up to 12 min. Ethanol consumption was reduced by as much as 50% for residence time in the loop up to 3 min. Very long exposure of yeast cells to excess nutrient levels (12 min) gave acetic acid formation. In a defined medium, the simulated feed zone effect increased biomass yield by up to 10%, but had no effect on ethanol levels. This study indicates that the feed zone effect on biomass yield in yeast fermentation, using complex substrates, will be negligible under fully aerobic conditions.
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    Effects of high product and substrate inhibitions on the kinetics and biomass and product yields during ethanol batch fermentation (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 289-297 
    Details
    ISSN: 0006-3592
    Keywords: batch alcoholic fermentation ; enthanol ; product inhibition ; substrate inhibition ; biomass yield ; product yield ; Saccharomyces cerevisiae ; lag time ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In ethanol fermentation, instantaneous biomass yield of the yeast Saccharmoyces cerevisiae was found to decrease (from 0.156 to 0.026) with increase in ethanol concentration (from 0 to 107 g/L), indicating a definite relationship between biomass yield and product inhibition. A suitable model was proposed to describe this decrease which incorporates the kinetic parameters of product inhibition rather than pure empirical constants. Substrate inhibition was found to occur when substrate concentration is above 150 g/L. A similar definite relationship was observed between substrate inhibition and instantaneous biomass yield. A simple empirical model is proposed to describe the declines in specfic growth rate and biomass yield due to substrate inhibition. It is observed that product inhibition does not have any effect on product yield whereas substrate inhibition significantly affects the product yield, reflecting a drop in overall product yield from 0.45 to 0.30 as the initial substrate concentration increases from 150 to 280 g/L. These results are expected to have a significant influence in formulating optimum fermentor design variables and in developing an effective control strategy for optimizing ethanol producitivity.
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    Protein immobilization to alumina supports: I. Characterization of alumina-organophosphate ligand interactions and use in the attachment of papain (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1319-1327 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; chemical adsorption ; alumina ; phosphate ; papain ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The chemical adsorption of organic phosphate compounds to alumina has been used to create surface linkers for protein immobilization. A number of particulate alumina supports were screened for their physical properties and ability to bind organic phosphate compounds. Two aluminas, termed C1 and CPC, were selected based on their suitability for subsequent testing as protein immobilization supports. Papain was successfully immobilized to these supports when derivatized with phosphate compounds containing free terminal carboxyl groups. Protein binding was enhanced when support carboxyl groups were activated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The level of papain immobilization was dependent upon the length of the linker used and the mass of protein exposed to the support. © 1992 John Wiley & Sons, Inc.
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    A computer-aided measuring system for the characterization of yeast populations combining 2D-image analysis, electronic particle counter, and flow cytometry (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 343-350 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; 2D-image analysis ; flow cytometry ; electronic particle counter ; comparison of size distributions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An integrated measuring system was developed that directly compares the shape of size distributions of Saccharomyces cerevisiae populations obtained from either microscopic measurements, electronic particle counter, or flow cytometer. Because of its asymmetric mode of growth, a yeast population consists of two different subpopulations, parents and daughters. Although electronic particle counter and flow cytometer represent fast methods to assess the growth state of the population as a whole, the determination of important cell cycle parameters like the fraction of daughters or budded cells requires microscopic observation. We therefore adapted a semiautomatic and interactive 2D-image processing program for rapid and accurate determination of volume distributions of the different sub-populations. The program combines the capacity of image processing and volume calculation by contour-rotation, with the potential of visual evaluation of the cells. High-contrast images from electron micrographs are well suited for image analysis, but the necessary air drying caused the cells to shrink to 35% of their hydrated volume. As an alternative, hydrated cells overstained with the fluorochrome calcofluor and visualized by fluorescence light microscopy were used. Cell volumes calculated from length, and diameter measurements with the assumption of an ellipsoid cell shape were underestimated as compared to volumes derived from 2D-image analysis and contour rotation, because of a deviating cell shape, especially in the older parent cells with more than one bud scar. The bimodal volume distribution obtained from microscopic measurements was identical to the protein distribution measured with the flow cytometer using cells stained with dansylchloride, but differed significantly from the size distribution measured with the electronic particle counter. Compared with the flow cytometer, 2-D image analysis can thus provide accurate distributions with important additional information on, for instance, the distributions of subpopulations like parents, daughters, or budded cells.
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    Reductive biotransformations of organic compounds by saccharomyces cerevisiae: Study of oxidoreductases involved using electrophoretic zymograms (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 457-461 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; biotransformations ; zymograms ; carbonyl reduction ; baker's yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The role of oxidoreductases in reduction of carbonyl compounds was investigated by application of zymogram techniques. Eight bands were observed using ethanol with nicotinamide adenine dinucleotide (NAD) as coenzyme. Bands observed with lactic acid and (R)-(-)-phenyl-1,2-ethanediol with nicotinamide adenine dinucleotide phosphate (NADP) had similar Rm values. 2-Hydroxyvalerate and malate manifested bands having similar Rm values and were active with both NAD and NADP. Based on their structural similarity and identical Rm values, oxidation of 1,4-cyclooctanediol (band #2) and cis-1,5-cyclooctanediol may be due to a common enzyme. The PAGE-zymogram technique may be used on a preparative scale to facilitate purification and full characterization on the observed stained bands.
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    Protein immobilization to alumina supports: II. Papain immobilization to alumina via organophosphate linkers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1328-1336 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; papain ; alumina ; kinetics ; fluorescence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particulate aluminum oxides (alumina) were examined as supports for the immobilization of the proteolytic enzyme papain. Two alumina supports termed C1 and CPC were derivatized using organic phosphate linkers to create free carboxyl groups using a two-step process. Papain binding to these derivatized aluminas was performed using the water soluble carbodiimide 1-ethyl-3-(dimethylaminopropyl) carbodiimide. Reactions were optimal at 10 mM carbodiimide. The immobilized protein showed similar kinetic constants when compared to the solution protein. The pH dependence and thermal stability were essentially identical. The immobilized papain showed a blue shift in the intrinsic fluorescence emission maxima. Papain modified with the active site-specific fluorescent probe acrylodan showed overlapping emission maxima. These results are interpreted as retention of the hydrophobic environment of the active site with a perturbation in the structure of the rest of the protein caused by its association with the negatively charged surface. © 1992 John Wiley & Sons, Inc.
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    Cultivator for NMR studies of suspended cell cultures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1359-1366 
    Details
    ISSN: 0006-3592
    Keywords: NMR studies ; cell cultures ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When nuclear magnetic resonance (NMR) spectroscopy is employed for physiological experiments with suspended cells, providing for adequate nutrient and oxygen delivery is particularly important, because the inherent insensitivity of NMR requires that concentrated cell suspensions be used. In addition, it is desirable to be able to manipulate the growth rate of cells during a NMR experiment. To address these concerns, a continuous cell cultivator that provides convective oxygen and nutrient transport has been constructed for NMR experiments. The NMR detector coil is located within the cultivator volume. The location is advantageous because the rapid exchange of cells in and out of the coil leads to a small apparent spin lattice relaxation time, thus allowing for rapid pulsing and fast signal averaging. In this article we present the physical principles on which the cultivator's design is based. 31P spectra showing the response of continuously cultivated Saccharomyces cerevisiae cultures to a phosphate bolus and growth rate shift are then given. © 1992 John Wiley & Sons, Inc.
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    Lactose/whey utilization and ethanol production by transformed Saccharomyces cerevisiae cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 799-805 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; lactose/whey ; biomass and ethanol production ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Strains of Saccharomyces cerevisiae transformed with a multicopy expression vector bearing both the Escherichia coli β-galactosidase gene under the control of the upstream activating sequence of the GAL1-10 genes and the GAL4 activator gene release part of β-galactosidase in the growth medium. This release is due to cell lysis of the older mother cells; the enzyme maintains its activity in buffered growth media. Fermentation studies with transformed yeast strains showed that the release of β-galactosidase allowed an efficient growth on buffered media containing lactose as carbon source as well as on whey-based media. The transformed strains utilized up to 95% of the lactose and a high growth yield was obtained in rich media. High productions of ethanol were also observed in stationary phase after growth in lactose minimal media.
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    Activity and stability of an entrapped-cell system for the Δ1-dehydrogenation of steroids in organic media (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1123-1127 
    Details
    ISSN: 0006-3592
    Keywords: steriod Δ1-dehydrogenation ; immobilization ; Arthrobacter simplex ; polyurethane ; organic media ; thermostability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Whole Arthrobacter simplex cells entrapped in κ-carra-geenan or in two types of polyurethane foam, or adsorbed on silanized Celite, were tested for the Δ1-dehydrogenation of hydrocortisone and its derivatives in organic media. Catalytic activity and stability levels were evaluated for the immobilized cells in buffer with 2.5% (vol/vol) methanol, and in three buffer-saturated solvents (n-octan-1-ol, n-decan-1-ol, and chloroform). The addition of glutamate to the immobilization support stabilized the activity of the immobilized cells in the tested organic media. The system with polyurethane (HYPOL6100)-entrapped cells (with coimmobilized glutamate) in n-decan-1-ol provided the highest long-term activity levels. Several factors involved in the polyurethane-entrapment procedure were also studied. © 1992 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260400918
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    Reductive biotransformation by wild type and mutant strains of Saccharomyces cerevisiae in aqueous-organic solvent biphasic systems (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 870-876 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; benzyl alcohol ; reductive biotransformation ; biphasic systems ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Whole cells of Saccharomyces cerevisiae analyzed the conversion of benzaldehyde to benzyl alcohol in aqueous-organic biphasic media. Reaction rate increased dramatically as moisture content of the solvent was increased in the range 0% to 2%. The highest biotransformation rates were observed when hexane was used as organic solvent. Benzaldehyde was also converted to benzyl alcohol by a cell-free crude extract in biphasic systems containing hexane, although the rate of product formation was much lower. Mutant strains of S. cerevisiae lacking some or all of the ADH isoenzymes, ADH I, II, and III, manifested similar rates for bioconversion of benzaldehyde to benzyl alcohol in both aqueous and two-phase systems. In general, conversion rates observed in aqueous media were 2 to 3 times higher than those observed in hexane containing 2% moisture.
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    Fermentation kinetics of recombinant yeast in batch and fed-batch cultures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 103-109 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; pRB58 ; invertase expression ; fed batch ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fed-batch cultures of recombinant microorganisms have attracted attention as they can separate cell growth stage from cloned-gene expression phase during fermentations. In this work, the effect of different glucose feeding strategies on cell growth and cloned gene expression was studied during aerobic fed-batch fermentations of recombinant yeast, containing the plasmid pRB58. The plasmid contains the yeast SUC2 gene, which codes for the enzyme invertase. Some feeding policies resulted in a constant glucose concentration inside the fermentor, while others deliberately introduced a cyclic variation. The cell mass yield was found to be higher at low glucose concentrations, thus indicating a shift to the more energy-efficient respiratory pathway. The SUC2 gene expression was derepressed at glucose levels below 2 g/L. The response of specific invertase activity to changes in the medium glucose concentration was found to be almost immediate.
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    Anomeric specificity of glucose uptake systems in Lactococcus cremoris, Escherichia coli, and Saccharomyces cerevisiae: Mechanism, kinetics, and lmplications (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 137-146 
    Details
    ISSN: 0006-3592
    Keywords: anomeric specificity ; mechanism of glucose uptake ; Lactococcus cremoris ; Escherichia coli ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mechanism and kinetics of the glucose uptake systems of three representative microorganisms are studied during cultivation in a chemostat. The three microorganisms are Lactococcus cremoris, Escherichia coli, and Saccharomyces cervisiae. Two models describing respectively competitive and independent uptake of the two glucose anomers are tested on experimental data where α- and β-glucose are determined by flow injection analysis after pulse addition of the pure anomers to a chemostat. The very accurate experimental results are used to give a convincingly clear model discrimination for all three microorganisms. The uptake of glucose by S. cervisiae occurs by a competitive mechanism with preference for α-glucose (Kα = 32 mg/L and Kβ = 48 mg/L). Surprisingly, the glucose uptake by the two bacteria is shown to be mediated by anomer specific transport systems with no competitive inhibition from the other glucose anomer. This novel finding has not been described in the literature on the phosphotransferase system. In L. cremoris the relative uptake rates of the glucose anomers match the equilibrium composition exactly (36% α-glucose). In E. coli the relative uptake rate of α-glucose at glucose unlimited growth is 26%, which means preference for β-glucose. However, the saturation constants of the two sites in E. coli are Kα = 2 mg/L and Kα = 15 mg/L, and a preference for α-glucose is exhibited at very low glucose concentrations. The results are of considerable improtance in relation to enzyme based on-line measurements during fermentations as well as to the modeling of glucose limited growth and product formation.
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    URL: http://dx.doi.org/10.1002/bit.260400119
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    Optimization of accessible catalase activity in polyacrylamide gel-immobilized Saccharomyces cerevisiae (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 638-642 
    Details
    ISSN: 0006-3592
    Keywords: catalase ; Saccharomyces cerevisiae ; polyacrylamide gel ; immobilization ; permeabilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The permeabilization of Saccharomyces cerevisiae (baker's yeast), either before or after immobilization in polyacrylamide gel (PAG), has been examined as a means to increase the catalase activity of PAG-immobilized yeast cells. Prior permeabilization of the cells resulted in large losses of catalase activity during immobilization, but permeabilization after immobilization produced increases in the catalase activity of yeast/PAG particles. A dependence of the accessible catalase activity on the concentration of polyacrylamide in permeabilized yeast/PAG particles, and on the method of permeabilization of the immobilized cells, was observed. Optimal levels of stable catalase activity (1000-2000 IU/g PAG particles; ca. 5%-10% of total available activity) were obtained by immobilizing yeast cells (0.5 g wet cells/mL gel) in 10% (w/v) PAG, followed by permeabilization of the entrapped cells with either cetyltrimethylammonium bromide, Triton X-100 and one freeze-thaw, or five freeze-thaw cycles. © 1992 John Wiley & Sons, Inc.
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    Application of polystyrene-bound invertase to continuous sucrose hydrolysis on pilot scale (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 997-1003 
    Details
    ISSN: 0006-3592
    Keywords: invertase ; sucrose hydrolysis ; polystyrene resin ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Invertase from baker's yeast (Saccharomyces cerevisiae) covalently bound to a macroporous polystyrene anion-exchange resin via glutaraldehyde was applied to continuous sucrose hydrolysis in packed bed-reactors. The process was scaled up from 3-mL laboratory reactors via 0.3-L reactors to pilot-scale 50-L reactors without significant loss of efficiency. The described process allows the production of a wide spectrum of invert sugar syrups with high purity in continuous procedure. The 50-L reactor was used under process conditions 1 year without significant loss of productivity at a temperature of 40°C. A productivity of 760 g/h was obtained with 1 L invertase-polystyrene complex using a 2.5M sucrose solution as substrate. © 1992 John Wiley & Sons, Inc.
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    Continuous hydrolysis of olive oil by immobilized lipase in organic solvent (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 748-752 
    Details
    ISSN: 0006-3592
    Keywords: lipase ; immobilization ; DEAE-sephadex ; organic solvent ; continuous hydrolysis reaction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipase (EC 3.1.1.3) from Candida rugosa was immobilized with DEAE-Sephadex A50, Sephadex G50, Sephadex LH-20, Amberlite IRA94, and Amberlite XAD-7. The enzye immobilized with DEAE-Sephadex A50 was found to be most effective for continuous hydrolysis of olive oil in isooctane. For the continuous reaction, 0.2 g of dry immobilized enzyme was swollen with predetermined amount of water, and packed in a glass column reactor. When the organic solvent (Isooctane) containing olive oil substrate was cocurrently fed with aqueous buffer, the two phases were evenly distributed throughout the packed bed without surfactant supplement or prior mixing of the two phases. A small amount of the surfactant (AOT) was used only in packing procedure, and no additional surfactant was necessary thereafter. Effects of initial water content of the swollen gel, buffer types, and strength were examined in the continuous reaction. Our results suggest that the operational half-life was affected by desorption of the bound enzyme. Under the conditions of 20% olive oil in isooctane and 25 mM triethanolamine buffer (pH 7.0), operational half life was 220 h at 30°C. The reactor was also operable with n-hexane, but the operational stability of the immobilized enzyme in n-hexane was only half of that in isooctane. Our results indicate that various enzyme carrier having hydrophilic or amphiphilic properties could be used for two-phase continuous reaction in packed-bed column, reactor without any surfactant supply or prior dispersion of the two immiscible phases. © 1992 John Wiley & Sons, Inc.
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    Kinetic studies on urea hydrolysis by immobilized urease in a batch squeezer and flow reactor (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1203-1209 
    Details
    ISSN: 0006-3592
    Keywords: urease ; immobilization ; polyurethane foam ; biofilm reactor model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The immobilization of urease on the reticulated polyurethane foam, and the kinetic phenomenon of urea hydrolysis by the resulting immobilized urease in both batch squeezer and circulated flow reactors were studied. Urease was immobilized with bovine serum albumin and glutaraldehyde on polyurethane foam support of 7 to 15 μm thickness. The residual apparent activity of urease after immobilization was about 50%. The good hydrodynamic property and flexibility of polyurethane foam were retained in solution after immobilization. A modified biofilm reactor model was used to describe the kinetic phenomenon of urea hydrolysis in both batch squeezer and circulated flow reactors. The characteristic parameters of the reactor model for both bioreactors were obtained by combining the Rosenbrock optimization method, the Rungs-Kutta method, and the Newton-Raphson method. The best-fit results were in good agreement with the experimental data. This study suggests another application of polyurethane foam in enzyme immobilization and immobilized enzyme reactors, which offers potential for practical applications in various bioreactors. © 1992 John Wiley & Sons, Inc.
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    Studies of the cell-wall properties of Saccharomyces cerevisiae during fermentation (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1309-1318 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; fermentation ; cell wall ; surface electrochemistry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cell-wall properties of three strains of the yeast Sacharomyces cerevisiae have been experimentally studied at various times during fermentation. The cell walls have been characterized by electrophoretic mobility measurements, from which zeta potentials may be calculated. They have also been characterized by computerized pH titration, which gives direct information on the number and nature of groups in the yeast cell wall. The data have been quantitatively analyzed in three ways. First, a simplified analysis of the electrokinetic data of a type used by previous workers has been applied. Second, such a simplified analysis of the electrokinetic data has been developed more rigorously by means of a two-dimensional site-dissociation model of the outer cell wall-solution interface. Third, a description of the yeast cell-wall electrochemical properties in terms of a three-dimensional gel model incorporating site dissociation has been developed. The advantages and disadvantages of the three analyses are discussed. Only the three-dimensional gel model can account simultaneously for both the electrokinetic and pH surface titration data. It provides new insights into the changes that occur to the yeast cell wall during fermentation. © 1992 John Wiley & Sons, Inc.
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    Continuous production of fructose syrup and ethanol from hydrolysed Jerusalem artichoke juice (1991)
    Springer
    Journal of industrial microbiology and biotechnology 7 (1991), S. 131-135 
    Details
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Jerusalem artichoke ; High-fructose syrup ; Ethanol ; Immobilized yeast cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The results from this study showed that Jerusalem artichoke juice can be used for the production of very enriched fructose syrup by selective conversion of glucose to ethanol in a continuous process using immobilized cells ofSaccharomyces cerevisiae ATCC 36859. The product contained up to 99% of the total carbohydrates as fructose compared to 76% in the feed. Using Jerusalem artichoke juice supplemented with some glucose a product was obtained with 7.5% w/v ethanol which made ethanol recovery economically favourable. It was found that some fructose was consumed in these continuous processes; the glucose/fructose conversion rate ratio was regulated by the glucose concentration in the product stream.
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    Analytical differentiation of wine fermentations using pure and mixed yeast cultures (1991)
    Springer
    Journal of industrial microbiology and biotechnology 7 (1991), S. 181-189 
    Details
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Torulaspora delbrueckii ; Aroma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Thirty-three fermentations of Pedro Ximénez grapes, collected in three degrees of ripeness, were carried out by inoculation with three types of inoculum: pure cultures ofSaccharomyces cerevisiae races and ofTorulaspora delbrueckii, indigenous yeasts, and mixed cultures of indigenous yeasts enriched with the pure cultures. By means of variance analysis 21 compounds were determined whose final concentrations in the wines significantly depended on the musts, the inocula or both. Eleven products that depended significantly on the inocula were subjected to a discriminant analysis in which most of the pure cultures gathered in a discriminant space area different from that occupied by the indigenous yeasts. The centroids corresponding to most of the mixed cultures were shifted to the central area of the discriminant space, moved away from their corresponding pure cultures and approached the indigenous yeasts. The results show a high similarity between the fermentations carried out with mixed cultures with the addedS. cerevisiae races and those fermentations carried out with the indigenous yeasts, with regard to those compounds which were significantly dependent on the inocula.
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    High density cultivation of BSK cells on sintered alumina ceramic foam support (1991)
    Springer
    Cytotechnology 5 (1991), S. 233-241 
    Details
    ISSN: 1573-0778
    Keywords: high cell density ; ceramic ; BHK ; perfusion system ; immobilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A perfusion system which utilizes a porous ceramic core has been tested for the cultivation of transformed BHK cells which produce human transferrin. A design is presented in which cells are immobilized within the porous ceramic particle and are fed by continuous perfusion of batch liquid medium. It was found that more than 5×109 BHK cells could be supported within the 40 mL ceramic matrix, a ten-fold increase in cell density per unit surface area over the standard roller bottle cultures or a five-fold increase in volumetric cell density over suspension cultures. The cell specific productivity of human transferrin was similar to that observed in suspension culture. The system offers the advantages of significant reduction in serum requirements and the potential for scale-up.
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    URL: http://dx.doi.org/10.1007/BF00556293
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    Increased protein productivity from immobilized recombinant yeast (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1029-1036 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; protein production ; continuous culture Saccharomyces cerevisiae ; plasmid stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Saccharomyces cerevisiae strain Mc16/p520 has an unstable plasmid, p520, which directs production of a wheat α-amylase. The effects of immobilizing this microorganism on the plasmid stability and the specific productivity of the secreted α-amylase were investigated. Small gelatin beads were used as the support in both fluidized and packed bed configurations, and the yeast cells were attached by covalent cross-linking with glutaraldehyde. These data were then compared to those for nonimmobilized, suspension cells.Plasmid stability was increased for the immobilized cells during continuous culture at dilution rates both above and below washout. Continuous suspension cultures were not stable and rapidly lost the plasmid. Immobilization caused an increase in specific and volumetric productivity during continuous culture, with a packed bed design resulting in the highest specific productivity.
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    Oxygen uptake by entrapped hybridoma cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1050-1053 
    Details
    ISSN: 0006-3592
    Keywords: hybridomas ; immobilization ; oxygen ; respiration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxygen consumption by hybridoma cells immobilized in 1- and 3.9-mm-diameter calcium alginate beads was measured. The entrapped cells consumed oxygen at about 10 μmol/min per 109 cells, regardless of the bead size and cell loading. In contrast, the same cells in suspension culture respire at specific rates of 3-8 μmol/min per 109 cells (depending on the cell density). The growth rate of the immobilized cells was significantly reduced, while specific antibody production was comparable to that of free cells.
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    Optimization of pro-urokinase secretion from recombinant Saccharomyces cerevisiae (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 869-875 
    Details
    ISSN: 0006-3592
    Keywords: scu-PA ; pro-urokinase ; yeast ; respiratory quotient ; fermentation ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Secretion of a nonglycosylated form of human pro-urokinase, also known as single-chain urinary plasminogen activator (scu-PA), from Saccharomyces cerevisiae is described. A “supersecreting” yeast strain harboring multiple copies of integrated plasmids was grown batchwise and at constant respiratory quotient (RQ) in 20-L fermenters. Because the promoters used to drive expression of the pro-urokinase genes are not tightly regulated, secretion into the culture supernatant was growth associated. Although the final cell density achieved in the perturbed-batch fermentation (45 g dry wt/L) was less than that observed in the RQ-controlled culture (77 g dry wt/L), the scu-PA titer in the perturbed-batch fermentation (1863 IU/mL) was nearly twice that attained at constant RQ (1108 IU/mL). The effects on cell growth and scu-PA titer of other process variables (pH, temperature, phosphate concentration, and medium composition) are also discussed.
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    Diffusion of lactose in k-carrageenan/locust bean gum gel beads with or without entrapped growing lactic acid bacteria (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1041-1049 
    Details
    ISSN: 0006-3592
    Keywords: diffusion ; lactose ; get matrix ; immobilization ; growing cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effective diffusion coefficients (De) of lactose in κ-carrageenan (2.75% wt/wt)/locust bean gum (0.25% wt/wt) (LBG) gel beads (1.5-2.0-mm diameter)with or without entrapped lactic acid bacteria (LAB) were determined at 40°C. The effects of lactose concentration, bacteria strain (Streptococcus salivarius subsp. thermophilus and Lactobacillus casei subsp. casei) and cell content at various steps of the fermentation process (after immobilization, pre-incubation of the beads and successive fermentations) were measured on De as a first step for process modelling. Results were obtained from transiend concentration changes n well-stirred lactose solutions in which the beads were suspended. A mathematical model of unsteady-state diffusion in a sphere was used, and De was obtained from the best fit of the experimental data. Diffusivity of lactose in cell-tree beads was significantly lower than in pure water mainly because of the obstruction effect of the polymer chains and the hydration region. Furthermore, effective diffusivity and equilibrium partition factor were independent of lactose concentration in the range from 12.5 to 50 g/L. No significant difference was found for De (effective diffusivity) and Kp (partition) coefficients between beads entrapping S. thermophilus (approximately 5 × 109 CFU/mL) and cell-free beads. On the other hand higher cell counts obtained with L. casei (close to 1.8 × 1011 CFU/mL) increased mass transfer resistance resulting in lower effective diffusivities and Kp. Finally, the effects of the type of bacteria and their distribution in the beads on the diffusivity were also discussed.
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    URL: http://dx.doi.org/10.1002/bit.260380913
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    Growth and immobilization of tripterygium wilfordii cultured cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1285-1291 
    Details
    ISSN: 0006-3592
    Keywords: Tripterygium Wilfordii ; plant cell culture ; suspension ; medium ; immobilization ; bioreactor culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The plant Tripterygium wilfordii produces di- and triterpenes of interest for male contraception and treatment of arthritis and skin disorders. Cell line TRP4a obtained form this plant in 1981 was reported to produce these valuable compounds at yields (∼0.04% of the biomass dry weight) higher than found in the plant (0.001%). In order to improve this production, studies were carried out to determine the feasibility of eliminating the troublesome component of coconut milk originally used to culture this cell line. A defined formulation suitable for growth ad maintenance has been developed. This medium consisted of Gamborg's PRL4 or B5 medium supplemented with 2 mg L-1 2,4-dichlorophenoxyacetic acid and 20 g L-1 sucrose. Furthermore, monitoring of carbohydrate uptake revealed that T. wilfordii cells, contrary to many plant cell species, did not hydrolyze sucrose extra-cellularly before uptake. Replacement of this disaccharide by glucose or fructose increased specific growth rate from 0.15 to 0.25 day-1. As tripdiolide is reported to be present in broth extract in significant amounts, plant cell immobilization technology offers a promising alternative to suspension cultures, especially in view to on line harvesting of the product. Surface immobilized T. wilfordii cell cultures were successfully carried out in 2-L bioreactors. Their biomass production and carbohydrate uptake were comparable to those observed for shake flask grown suspension cultures. Higher nitrate and ammonium uptake were found in immobilized cultures.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260381105
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    Lipase kinetics: Hydrolysis of triacetin by lipase from Candida cylindracea in a hollow-fiber membrane reactor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 727-732 
    Details
    ISSN: 0006-3592
    Keywords: lipase kinetics ; Candida cylindracea ; hydrolysis of triacetin ; hollow-fiber membrane reactor ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The aptitude of a hollow-fiber membrane reactor to determine lipase kinetics was investigated using the hydrolysis of triacetin catalyzed by lipase from Canadida cylindracea as a model system. The binding of the lipase to the membrane appears not to be very specific (surface adsorption), and probably its conformation is hardly altered by immobilization, resulting in an activity comparable to that of the enzyme in its native form. The reaction kinetics defined on the membrane surface area were found to obey Michaelis-Menten kinetics. The specific activity of the lipase in the membrane reactor was found to be significantly higher than in an emulsion reactor. The activity and stability of the enzyme immobilized on a hydrophilic membrane surface seem not to be influenced significantly by the choice of the membrane material. The hollow-fiber membrane reactor is a suitable tool to assess lipase kinetics in a fast and convenient way.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260380706
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  • 177
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    Use of microcalorimetric monitoring in establishing continuous energy balances and in continuous determinations of substrate and product concentrations of batch-grown Saccharomyces cerevisiae (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 447-458 
    Details
    ISSN: 0006-3592
    Keywords: energy balances ; Saccharomyces cerevisiae ; fermentation ; microcalorimetric monitoring ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Energy balance calculations were performed for different physiological states during batch growth of Saccharomyces cerevisiae with glucose as carbon and energy source. For the different physiological states, energy recoveries close to one were obtained, which permitted a continuous control that the constantly changing growth process was quantified accurately. During the respiro-fermantative phase of growth, during which glucose served as the carbon and energy source, a low-heat-yield value (ΔQx) of -8.6 kJ/g dry biomass formed was obtained. This low-heat-yield value was due to the mainly fermentative metabolism during the middle of this phase of growth. After a transition phase, the ethanol produced during the respiro-fermentative growth was respired. During this respiratory phase, the heat yield values increased markedly, resulting in a lowest value of -42.7 kJ/g. The low-heat-yield values of the respiro-fermentative growth is not a reflection of the most efficient metabolism of S. cerevisiae. On the contrary, during the middle of this phase, 74% of the energy input was dissipated as ethanol, 6% was dissipated as heat, and the energy conserved as biomass was just 13%, while during the early respiratory phase, 69% of the energy input was dissipated as heat, and 22% of the energy input was conserved as biomass. By mathematical modeling and direct monitoring on-line of the rate of heat production, continuous calculations of (1) glucose consumption, and (3) biomass production were performed, and were shown to correlate closely with measured values for the continuously changing growth process.
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    URL: http://dx.doi.org/10.1002/bit.260380503
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  • 178
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    Studies of the reductive biotransformation of selected carbonyl compounds by whole cells and extracts of baker's yeast, Saccharomyces carevisiae (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1280-1284 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; biotransformation ; oxidoreductases ; carbonyl ; stereospecific ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The progress of reductive biotransformations of a variety of earbonyl compounds by whole cells of baker's yeast was monitored with time. Biotransformations rates ranged from 0.11 to 112.12 mg product formed per g dry yeast per h. While rapid biotransformations of citronellal and ethyl benzoylformate were observed, complete conversion of substrate to product did not occur. Reductive conversions of ethyl- and methyl-acetoacetate went to completion in 6 and 12 h respectively. Ethyl mandelate was produced stereoselectively, favoring the (R)- stereoisomer and ethyl and methyl-3-hydroxybutyrate were produced with (S)-enantiospecificity. Yeast crude extract and resuspended presence of NAD(P)H. Ethyl benzoylformate and methyl-and ethyl-acetoacetate were preferentially reduced by yeast crude extract as compared to resuspended pellet and, in the case of the former two substrates, the reaction manifested a preference for NADPH over NADH.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260381104
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  • 179
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    Analysis of mass transfer for immobilized cells in an extractive lactic acid fermentation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 544-550 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; extractive fermentation ; Lactobacillus delbrueckii ; k-carrageenan ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of immobilization in extractive lactic acid fermentation by Lactobacillus delbrueckii is preferred. In this article, the mathematical simulations to examine the influences of substrate and product transport were performed to assess the overall performance. The simulations showed that transport of the substrate in k-carrageenan beads was not a rate limiting factor. However, the model observed significant buildup of inhibitory product in large beads. The model was validated through comparisons with the experimental results. Finally, the model was used to predict the performance of the extractive fermentation under different operating strategies.
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    URL: http://dx.doi.org/10.1002/bit.260370608
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    Methanol biosynthesis by covalently immobilized cells of Methylosinus trichosporium: Batch and continuous studies (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 551-556 
    Details
    ISSN: 0006-3592
    Keywords: Methylosinus trichosporium ; methanol biosynthesis ; immobilization ; batch and continuous studies ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The DEAE-cellulose linked cells of Methylosinus trichosporium displaying high specific methane mono-oxygenase activity (66 μmol methane oxidized/h mg cells) were used for methanol biosynthesis from biogas derived methane in a batch and a continuous cell reactor. The optimum cell-to-carrier ratio was determined to be 0.5 g cells/g dry weight cellulose. Batch experiments indicated that 100 mM phosphate ion concentration was necessary to inhibit further oxidation of methanol; excess oxygen supply favored methanol accumulation with an increase in methane conversion efficiency to 27%. A pulse of 40 mM sodium formate at the end of 6 h resulted in restoration of methanol accumulation by regenerating NADH2 required for the sustained activity of methane mono-oxygenase. Maximum methanol level of 50 μmol/mg cells was obtained in the batch reactor. In a standard 50-mL ultrafiltration continuous reactor, the covalently linked cells produced methanol at a continuous rate of 100 μmol/h for the first 10 h, after which the methanol accumulation rate fell low due to the depletion of NADH2. The methanol accumulation could be stimulated by supplying sodium formate (40 mM) in either 20 or 100 mM phosphate buffer. Maximum methanol accumulation rate of 267 μmol/h was obtained when 20 mM formate was supplied in the feed stream containing 100 mM phosphate ions, and this level of biosynthesis was maintained for over 72 h. The stoichiometric balance made at various points of formate addition indicated that the molar amount of methanol generated at steady state is dependent on the equimolar addition of sodium formate to the feed. The half-life t1/2 and thermal denaturation rate constant Kd were computed to be 108 h and 6.42 × 10-3 h-1, respectively.
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    URL: http://dx.doi.org/10.1002/bit.260370609
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    Characterization of the biochemical behavior of glucose oxidase entrapped in a polypyrrole film (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 854-858 
    Details
    ISSN: 0006-3592
    Keywords: Polypyrrole ; glucose oxidase ; immobilization ; autoinactivation ; thermodesactivation ; stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article reports the characterization of the biochemical behavior of glucose oxidase entrapped in polypyrrole. The immobilization of glucose oxidase in a polypyrrole film was performed by entrapment during the electropolymerization of pyrrole at a platinum electrode poised at 0.65 V vs. SCE in aqueous solution in a one-compartment electrochemical cell. Thin films of polypyrrole (0.11 μm) were obtained and the entrapped enzyme obeyed Michaelis kinetics, indicating no diffusional constraints of the substrate. Our results indicate that the entrapped glucose oxidase is more resistant to denaturation conditions such as alkaline pH and temperature (50 and 60°C) than the soluble form of the enzyme. The autoinactivation constant for the entrapped enzyme was also determined in presence of 0.25M of glucose and was 6.19 × 10-4 min-1, i.e., corresponding to a half-life value of 20 h. The results reported here show clearly that polypyrrole matrix has a strong stabilizing effect on the stucture and on the activity of glucose oxidase.
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    URL: http://dx.doi.org/10.1002/bit.260370909
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    Production of L-phenylacetyl carbinol by biotransformation: Product and by-product formation and activities of the key enzymes in wild-type and ADH isoenzyme mutants of Saccharomyces cerevisiae (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 493-498 
    Details
    ISSN: 0006-3592
    Keywords: L-phenylacetyl carbinol ; ADH isoenzymes ; ethanol ; benzyl alcohol ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The capacities of yeast wild-type and mutants strains known to lack specific ADH isoenzymes to produce L-phenylacetyl carbinol (PAC) and benzyl alcohol in biotransformation trials were also investigated. Pyruvate decarboxylase activity, responsible for PAC formation and ADH activity, which can participate in reduction of benzaldehyde to benzyl alcohol, was also determined in each strain. In addition, the capacity of each strain to produce ethanol was investigated. Mutant strains lacking all of the isoenzymes, ADH-I, ADH-II, and ADH-III, still exhibited some ADH activity and were capable of production of benzyl alcohol and ethanol.
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    URL: http://dx.doi.org/10.1002/bit.260380507
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    Development of a kinetic model for the alcoholic fermentation of must (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 742-748 
    Details
    ISSN: 0006-3592
    Keywords: alcohol ; fermentation ; ethanol ; Saccharomyces cerevisiae ; model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We Propose a kinetic expression which accounts for the temperature dependence of ethanol yield losses in batch alcoholic fermentation. Moreover, the characteristic parameters of the microbial growth equation have been calculated for Saccharomyces cerevisiae under typical wine industry conditions. A substrate consumption equation is established which minimizes possible model deviations in the latter process stages. Experimental data were obtained in the laboratory and the proposed equations were then applied at an industrial level (2.5 × 104 L) where they described the data well.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260380708
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    Production of monoclonal antibody using free-suspended and immobilized hybridoma cells: Effect of serum (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 821-830 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; immobilization ; serum ; flow cytometry ; antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of serum on cell growth and monoclonal antibody (MAb) productivity was studied in a repeated fedbatch mode using both free-suspended and immobilized S3H5/γ2bA2 hybridoma cells. In the suspension culture, serum influenced the cell growth rate but not the specific MAb productivity. The average specific growth rate of the suspension culture in medium containing 10% serum was approximately 0.99 ± 0.12 day-1 (±standard deviation), while that in medium containing 1% serum was approximately 0.73 ± 0.12 day-1. The specific MAb productivity was almost constant at 3.69 ± 0.57 μg/106 cells/day irrespective of serum concentration reached a maximum at ca. 1.8 × 106 cells/mL of medium in 10% serum medium, and the cell concentration was gradually reduced to 1%. The specific MAb productivity of the immobilized cells was more than three times higher than that of the free-suspended cells. The amount of serum in the medium did not influence the specific MAb production rate of the immobilized cells. The maintenance of high cell concentration and the enhanced specific MAb productivity of the immobilized cell culture resulted in a higher volumetric MAb productivity. In addition, MAb yield in the immobilized cell culture with medium containing 1% serum was 2.2 mg/mL of serum, which was approximately three times higher than that in the suspension culture.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260380804
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    Biomass axial distribution in airlift bioreactor with yeast and plant cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1325-1330 
    Details
    ISSN: 0006-3592
    Keywords: biomass distribution ; bioreactor, loop airlift ; Saccharomyces cerevisiae ; Phaseolus vulgaris ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study was aimed at determining the degree of biomass homogeneity in the various parts of an internal loop airlift bioreactor, thus verifying the assumption, often made in bioreactor studies, of a well-mixed liquid-biomass system. Following characterization of the hydrodynamics of the vessel with water, the axial biomass distribution in the riser and downcomer was determined for plant and yeast cell suspensions of 5.8, 8.5, and 12.5 g DW/L Phaseolus vulgaris and of 30 and 46 g DW/L Saccharomyces cerevisiae. The airlift bioreactor with a surface ratio AD/AD of 1.04 and aspect ratio of 4.95 was investigated under various aeration rates. The yeast cells were found to be distributed practically uniformly throughout the vessel at the aeration rates of 0.1-1.45 vvm. However, in the case of the denser and cluster-forming plant cells, a clear trend of a gradual bio-mass accumulation in the downcomer, a slightly lower but uniform biomass loading in the riser, and a slightly higher biomass concentration in the gas-liquid separator was observed at the lower aeration rates of 0.1-0.61 vvm. In the case of powderized calcium carbonate (55g/L) often used in fermentations of organic acids, a slight trend of a gradual accumulation of solids towards the bottom parts in both the downcomer and riser was observed. A better representative sampling location, in terms of solids and biomass loading, seems to be in the middle part of the vessel. It is suggested that airlift bioreactors with higher aspect ratios (〉5) may be prone to a more significant inhomogeneity of solids (biomass and particles).
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    URL: http://dx.doi.org/10.1002/bit.260381110
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    Biotransformation of aromatic aldehydes bySaccharomyces cerevisiae: Investigation of reaction rates (1989)
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 49-53 
    Details
    ISSN: 1476-5535
    Keywords: l-Phenylacetyl carbinol ; Saccharomyces cerevisiae ; Yeast ; Benzaldehyde ; Biotransformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The rate of production ofl-phenylacetyl carbinol bySaccharomyces cerevisiae in reaction mixtures containing benzaldehyde with sucrose or pyruvate as cosubstrate was investigated in short 1 h incubations. The effect of yeast dose rate, sucrose and benzaldehyde concentration and pH on the rate of reaction was determined. Maximum biotransformation rates were obtained with concentrations of benzaldehyde, sucrose and yeast of 6 g, 40 g and 60 g/l, respectively. Negligible biotransformation rates were observed at a concentration of 8 g/l benzaldehyde. The reaction had a pH optimum of 4.0–4.5. Rates of bioconversion of benzaldehyde and selected substituted aromatic aldehydes using both sucrose and sodium pyruvate as cosubstrate were compared. The rate of aromatic alcohol production was much higher when sucrose was used rather than pyruvate.o-Tolualdehyde and 1-chlorobenzaldehyde were poor substrates for aromatic carbinol formation although the latter produced significant aromatic alcohol in sucrose-containing media. Yields of 2.74 and 3.80 g/l phenylacetyl carbinol were produced from sucrose and pyruvate, respectively, in a 1 h reaction period.
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    High solids fermentation of hydrolysates of wheat starch B in a continuous dynamic immobilized biocatalyst bioreactor (1989)
    Springer
    Journal of industrial microbiology and biotechnology 4 (1989), S. 81-84 
    Details
    ISSN: 1476-5535
    Keywords: Ethanol fermentation ; Wheat starch ; Saccharomyces cerevisiae ; immobilization ; Continuous dynamic immobilized biocatalyst bioreactor ; Biocatalyst bioreactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A simple and efficient method of conversion of wheat starch B to ethanol was investigated. Employing a two-stage enzymatic saccharification process, 95% of the wheat starch was converted to fermentable sugars in 40 h. From 140 g/l total sugars in the feed solution, 63.6 g/l ethanol was produced continuously with a residence time of 3.3 h in a continuous dynamic immobilized biocatalyst bioreactor by immobilized cells ofSaccharomyces cerevisiae. The advantages and the application of this bioreactor to continuous alcoholic fermentation of industrial substrates are presented.
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    URL: http://dx.doi.org/10.1007/BF01569698
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    Production of erythropoietin by BHK cells growing on the microcarriers trapped in alginate gel beads (1989)
    Springer
    Cytotechnology 2 (1989), S. 141-145 
    Details
    ISSN: 1573-0778
    Keywords: alginate ; erythropoietin ; high-density ; immobilization ; microcarrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Baby hamster kidney (BHK) cells engineered to produce recombinant human erythropoietin (EPO) were cultured at high density on microcarriers entrapped by calcium alginate gel particles. In this system, the BHK cells proliferated not only on the microcarriers but also in vacant spaces in the alginate gel particles. These spaces contributed greatly to high-density cultivation of the cells and a high productivity of EPO.
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    URL: http://dx.doi.org/10.1007/BF00386147
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    Osmotic pressure effects and intracellular accumulation of ethanol in yeast during fermentation (1988)
    Springer
    Journal of industrial microbiology and biotechnology 2 (1988), S. 365-372 
    Details
    ISSN: 1476-5535
    Keywords: Osmotic pressure ; Intracellular ethanol ; Yeast ; Nutrient ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The intracellular accumulation of ethanol in yeast and its potential effects on growth and fermentation have been topics of controversy for the past several years. The determination of intracellular ethanol based on the exclusion of [14C]sorbitol to estimate aqueous cell volume was used to examine the question of intracellular ethanol accumulation. An intracellular accumulation of ethanol inSaccharomyces cerevisiae was observed during the early stages of fermentation. However, as fermentation continued, the intracellular and extracellular concentrations of ethanol became similar. Increasing the osmotic pressure of the medium with glucose or sorbitol was observed to cause an increase in the intracellular ethanol concentration. Associated with this was a decrease in yeast growth and fermentation rates. In addition, increasing the osmotic pressure of the medium was observed to cause an increase in glycerol production. Supplementation of the media with excess peptone, yeast extract, magnesium sulfate and potassium phosphate was found to relieve the detrimental effects of high osmotic pressure. Under these conditions, though, no effect on the intracellular and extracellular ethanol distribution was observed. These results indicate that nutrient limitation, and not necessarily intracellular ethanol accumulation, plays a key role during yeast fermentations in media of high osmolarity.
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    An immobilized hybridoma culture perfusion system for production of monoclonal antibodies (1988)
    Springer
    Cytotechnology 1 (1988), S. 331-337 
    Details
    ISSN: 1573-0778
    Keywords: hybridoma ; immobilization ; monoclonal antibodies ; perfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A fixed bed perfusion system for hybridoma cell immobilization is presented. The system consists of a culturing vessel (300 ml total volume) in which polyurethane (PU) sponges in the form of small cubes of about 5 mm sides are packed. Cells are immobilized by physical entrapment in the foam matrix. By entrapment of the cells in the pores of the matrix high cell concentration can be maintained in a mechanically protected environment. Medium is continuously circulated by an airlift pump mounted in the cell-free chamber (700 ml total volume). Medium flow rate, feeding rate, dissolved oxygen, pH, nutrient uptake and waste product formation can be easily monitored and controlled. Steady state conditions are established with medium dilution rates of 1.0–1.5 reactor volume per day. The steady state is characterized by a constant cell density, constant culture volume and constant glucose and lactate levels. Cell-free supernatant is collected continuously in a cold room adjacent to the 37°C culture room. Monoclonal antibodies (MAb) are produced at a concentration of 150–200 μg/ml for several weeks. An important feature of the system is the capacity to maintain a population of cells after the growth phase in a non-proliferating state for extended time periods expressing high titers of MAb.
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    URL: http://dx.doi.org/10.1007/BF00365078
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    Selection in yeast I: Assessing genetic stability and relative fitness of commercial yeasts (1987)
    Springer
    Journal of industrial microbiology and biotechnology 2 (1987), S. 159-165 
    Details
    ISSN: 1476-5535
    Keywords: Yeast ; Genetic stability ; Saccharomyces cerevisiae ; Selection ; Reproductive fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The potential for changes in allele frequencies in yeast populations by selection was examined. Cells from the wine yeastSaccharomyces cerevisiae (strain Montrachet) were grown over a large number of generations using two different culturing techniques, each with two variations: serial transfers on WLN agar plates with and without UV irradiation, and continuous culture in autoclaved and in filter-sterilized grape must. A low frequency of variant isozyme patterns was found in samples taken at the end of the experiment. Growth rates in must and on agar plates were also examined, and it was found that all samples were faster-growing than the original strain, to varying degrees. Applications for the selection system developed are discussed.
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    URL: http://dx.doi.org/10.1007/BF01569423
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    Selection in yeast II: The fitness distribution of new mutations inSaccharomyces cerevisiae and its use in a computer simulation (1987)
    Springer
    Journal of industrial microbiology and biotechnology 2 (1987), S. 167-174 
    Details
    ISSN: 1476-5535
    Keywords: Selection ; Yeast ; Fitness distribution ; Mutation ; Saccharomyces cerevisiae ; Computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The fitness distribution of new mutations inSaccharomyces cerevisiae strain Montrachet was determined for cells on agar irradiated for four periods of time with ultraviolet light. The fitness distributions were obtained by converting a large number of colony diameters into relative fitnesses. The distributions were then used to perform a computer simulation with the purpose of predicting the potential of a stock culture to increase in general fitness through selection, given a frequency and magnitude of mutations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569424
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  • 193
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    Optically monitoring Baker's yeast (Saccharomyces cerevisiae) growing in an air-fluidized/expanded potato starch matrix (1987)
    Springer
    Journal of industrial microbiology and biotechnology 2 (1987), S. 187-193 
    Details
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Fermentation ; Air-fluidized fermentation ; Semi-solid fermentation ; Yeast cell concentration in starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In order to study cell behavior in solid fermentation processes, model systems using gelatin and starch have been developed to track Baker's yeast growth. The difficulty in estimating the cell concentration within solid materials arises because both the solid material and the cellular material contribute to the measurement (such as optical resistance). In general, however, the two materials cannot be easily separated, hence the need to measure the cells along with the solid supporting material. A simple spectrophotometric method has previously been shown to work well in both aerated submerged batch cultures and aerated static solid cultures. The optical approach is applied here to monitor a more complex solidified system: cell growth in a novel air-fluidized/expanded bed of yeast growing on a starch matrix. Conventional assays for reducing sugar, total extracellular protein, and extracellular lysine were also applied to monitor yeast behavior in this new system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569427
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  • 194
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    Biosynthesis of superoxide dismutase and catalase inSaccharomyces cerevisiae: effects of oxygen and cytochromec deficiency (1986)
    Springer
    Journal of industrial microbiology and biotechnology 1 (1986), S. 187-193 
    Details
    ISSN: 1476-5535
    Keywords: Saccharomyces cerevisiae ; Cytochromec ; Superoxide dismutase ; Catalase ; Oxyradicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two strains ofSaccharomyces cerevisiae were used to study the synthesis of superoxide dismutase. One strain (cytochromec-deficient) contained 5–10% of the normal amounts of total cytochromec, while the other strain was a wild type. The cytochromec-deficient mutant had lower specific growth rate, growth yield, and oxygen uptake than the wild type. The superoxide dismutase and catalase activities, in both strains, were significantly lower under anaerobic than under aerobic conditions. Furthermore, under aerobic conditions the mutant contained higher levels of superoxide dismutase than the wild type which may be attributed to the higher intracellular flux of superoxide radicals caused by the cytochromec deficiency. The mutant also showed a lower level of catalase which was due to glucose repression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569271
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  • 195
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    Immobilization and characterization of Saccharomyces cerevisiae in crosslinked, prepolymerized polyacrylamide-hydrazide (1982)
    Springer
    Applied microbiology and biotechnology 16 (1982), S. 75-80 
    Details
    ISSN: 1432-0614
    Keywords: Immobilization of yeast ; Saccharomyces cerevisiae ; Ethanol production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Baker's yeast (Saccharomyces cerevisiae) was immobilized in gels made of prepolymerized, linear, water soluble polyacrylamide, partially substituted with acylhydrazide groups. Gelation was effected by the addition of controlled amounts of dialdehydes (e.g. glyoxal). The immobilized yeasts retained full glycolytic activity. Moreover, the entrapped cells were able to grow inside the chemically corsslinked gel during continuous alcohol production. Glyoxal was found to be the most favourable crosslinking agent for this system. the system employed allowed for the free exchange of substrate and products. The gel surrounding the entrapped cells had no effect on temperature stability profile. On the other hand, substantial enhancement in survival of cells in presence of high ethanol concentrations was recorded for the entrapped yeast. The capability of the immobilized yeast to carry out continuous conversion of glucose to ethanol was demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500730
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  • 196
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    Uptake of cadmium and zinc by yeast: Effects of co-metal ion and physical/chemical treatments
    Amsterdam : Elsevier
    Bioresource Technology 50 (1994), S. 113-117 
    Details
    ISSN: 0960-8524
    Keywords: Cadmium ; Saccharomyces cerevisiae ; antagonism ; non-interaction ; physical/chemical treatment ; synergism ; zinc
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0960-8524(94)90062-0
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  • 197
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    Continuous glycerol production in a packed-bed bioreactor with immobilized cells of Saccharomyces cerevisiae
    Amsterdam : Elsevier
    Bioresource Technology 49 (1994), S. 209-212 
    Details
    ISSN: 0960-8524
    Keywords: Saccharomyces cerevisiae ; glycerol ; immobilized cells
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0960-8524(94)90041-8
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  • 198
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    Losses and transformation of nitrogen during composting of poultry manure with different amendments: An incubation experiment
    Amsterdam : Elsevier
    Bioresource Technology 47 (1994), S. 265-273 
    Details
    ISSN: 0960-8524
    Keywords: Ammonia volatilization ; ammonification ; composting ; elemental sulphur ; immobilization ; poultry manure ; zeolite
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0960-8524(94)90190-2
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  • 199
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    A strain of Saccharomyces cerevisiae which grows efficiently on starch
    Amsterdam : Elsevier
    Enzyme and Microbial Technology 7 (1985), S. 220-224 
    Details
    ISSN: 0141-0229
    Keywords: Saccharomyces cerevisiae ; Saccharomyces diastaticus ; Starch ; amylolytic enzymes ; biomass ; yeast
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/S0141-0229(85)80006-5
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  • 200
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    Computer-aided modeling and optimization for capsaicinoid production by immobilized Capsicum frutescens cells
    Amsterdam : Elsevier
    Enzyme and Microbial Technology 15 (1993), S. 710-715 
    Details
    ISSN: 0141-0229
    Keywords: Capsicum ; capsaicinoids ; elicitors ; growth regulators ; immobilization ; optimization ; response surface methodology
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0141-0229(93)90074-C
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