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  • Articles  (5,507)
  • American Chemical Society  (3,996)
  • Springer  (1,511)
  • 1995-1999  (5,507)
  • 1997  (5,507)
  • Process Engineering, Biotechnology, Nutrition Technology  (5,507)
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  • Articles  (5,507)
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  • 1995-1999  (5,507)
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  • 1
    Electronic Resource
    Electronic Resource
    Editorial (1997)
    Springer
    Adsorption 3 (1997), S. 5-5 
    Details
    ISSN: 1572-8757
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133002
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  • 2
    Electronic Resource
    Electronic Resource
    Composite materials based on zeolite 4A for adsorption heat pumps (1997)
    Springer
    Adsorption 3 (1997), S. 33-40 
    Details
    ISSN: 1572-8757
    Keywords: adsorption heat pumps ; equivalent thermal conductivity ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Some additives and binders were chosen for the preparation of 4A-zeolite-based composites with high equivalent thermal conductivity for heat pumps application. Additives (SiC, Si3N4, graphite) and binders (PTFE, Al(OH)3) were tested for their effectiveness in terms of equivalent thermal conductivity and maximum water adsorption capacity of the composites. The influence of the equivalent thermal conductivity of the composite adsorbents on the specific power of the heat pump was also calculated. Results show a significant improvement in the equivalent thermal conductivity of the composite samples which are prepared using aluminum hydroxide as binder, over that of zeolite pellet beds. Such composite materials could be used to build adsorption heat pumps with higher specific power and, consequently, with lower investment cost.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133005
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  • 3
    Electronic Resource
    Electronic Resource
    Adsorption of nitrogen, methane, carbon monoxide, and their binary mixtures on aluminophosphate molecular sieves (1997)
    Springer
    Adsorption 3 (1997), S. 7-25 
    Details
    ISSN: 1572-8757
    Keywords: AlPO4 molecular sieves ; nitrogen adsorption ; methane adsorption ; carbon monoxide adsorption ; binary adsorption isotherms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Experimental isotherms describing the adsorption of pure N2, CH4 and CO in AlPO4-11, AlPO4-17, and AlPO4-18 were determined using the volumetric method at 40°C and at 23°C (AlPO4-11 only) over a pressure range up to 123 kPa, and subsequently fitted with the Langmuir or Freundlich equations, as well as the Flory-Huggins Vacancy Solution Theory equation. The capacities for the adsorbates investigated were found to depend on the geometry of the sieve pore size, as well as the molecular dimensions and the polority of the adsorbate involved. At 40°C and over the investigated pressure range, AlPO4-11 and AlPO4-17 adsorbed pure CH4 in the highest amounts, while AlPO4-18 had a slightly higher capacity for pure CO. The model parameters obtained by fitting the experimental pure-component isotherms permitted the prediction of binary adsorption information for the CO−N2, CH4−CO, and CH4−N2 gas mixtures at 101.3 kPa total pressure, using the Extended Langmuir Model, the Ideal Adsorbed Solution Theory, and/or the Flory-Huggins Vacancy Solution Theory for mixtures. An explanation of the behaviour predicted by each model for each adsorption system is attempted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133003
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  • 4
    Electronic Resource
    Electronic Resource
    Zeolites modified by CuCl for separating CO from gas mixtures containing CO2 (1997)
    Springer
    Adsorption 3 (1997), S. 27-32 
    Details
    ISSN: 1572-8757
    Keywords: CO adsorbent ; CO2 adsorption ; zeolite modification ; monolayer dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Although zeolites such as NaY and 13X adsorb CO2 much more than CO, the adsorption amount of CO2 and CO can be reversed if the zeolites are modified with CuCl. When zeolite NaY or 13X is mixed with CuCl and heated, high CO adsorption selectivity and capacity can be obtained. Isotherms show the adsorbents have CO capacity much higher than CO2. This is because CuCl has dispersed onto the surface of the zeolites to form a monolayer after the heat treatment and the monolayer dispersed CuCl can provide tremendous Cu(I) to selective adsorb CO and inhibit the CO2 adsorption. The monolayer dispersion of CuCl is confirmed by XRD and EXAFS studies. The loading of CuCl on the zeolites has a threshold below which the CuCl forms monolayer after heating and crystalline phase of CuCl can not be detected by XRD. An adsorbent of CuCl/NaY with CuCl content closed to the monolayer capacity shows very high CO selective adsorbability for CO2, N2, H2 and CH4. At temperature higher than room temperature, the adsorbent has even better CO selectivity for CO2. Using the adsorbent, a single-stage 4 beds PSA process, working at 70°C and 0.4 MPa to 0.013 MPa, can obtain CO product with purity 〉99.5% and yield 〉85%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133004
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  • 5
    Electronic Resource
    Electronic Resource
    Convection-diffusion of solutes in dynamic media (1997)
    Springer
    Adsorption 3 (1997), S. 41-54 
    Details
    ISSN: 1572-8757
    Keywords: liquid crystals ; moving bed system ; simulation ; purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We investigate convective-diffusive transport of a solute through a medium with properties that can be externally modulated in space and time. In particular, we focus on the effect of a front—a sharp transition in the convective velocity (v) and diffusivity (D)—on the evolution of the solute concentration profile. Numerical results show that by suitably moving the front during the process an anti-dispersive effect may be realized, in which the solute accumulates in a thin region close to the moving boundary. Our computations take into account the realistic case of a front having a small but finite thickness, and we find that the width of the concentration profile scales as $$\left( {1/\sqrt {Pe} } \right)$$ , where Pe is the Péclet number. This is in sharp contrast to the 1/Pe scaling observed for the ideal case of the singular front assumed in previous work. The effect of the thickness of the front and the magnitude of the drop inv andD, on the solute concentration profile has also been studied. These results are relevant in order to implement and optimize protocols that apply an externally controlled moving boundary for the purpose of separation. We also present experimental results characterizing solute transport across a stationary front, expected to display many features needed in a model for moving fronts. The concentration profile of electrophoretically mobile BSA-FITC within the boundary layer at a polyacrylamde gel-buffer interface were visualized by epifluorescence microscopy. Measured boundary layer thickness exceeded that predicted for even a finite interface, indicating that the length scale associated with real boundaries is relevant to the modeling problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133006
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  • 6
    Electronic Resource
    Electronic Resource
    Adsorbents from Waste materials (1997)
    Springer
    Adsorption 3 (1997), S. 81-91 
    Details
    ISSN: 1572-8757
    Keywords: activated carbon ; solid organic waste
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The possibility of using pyrolyzed wastes produced in already working incineration plants, as adsorbents for waste water treatment, was studied. Showing very poor adsorption properties, they were improved by steam activation technique used in the conventional activated carbon manufacturing. It is concluded that various organic waste materials can be converted to carbonaceous final products with a character similar to activated carbon. Their adsorption properties and pore size distribution are determined by the structure of the starting material. Although most of these samples have a low specific surface area, their pore volume is not negligible in the meso-and micropore range. Adsorption tests with model waste waters confirmed that adsorption properties are strongly influenced by the character of the suface. The adsorption capacity of these samples can be utilized for the treatment of strongly polluted industrial waste waters. Considering that the raw material ‘needed’ to manufacture these adsorbent is produced permanently and the adsorbents do not have to be regenerated, it might be worthwhile using these kinds of adsorbents in the primary treatment of industrial waste waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133009
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation and characterization of bimodal porous carbons derived from a styrene-divinylbenzene copolymer (1997)
    Springer
    Adsorption 3 (1997), S. 67-79 
    Details
    ISSN: 1572-8757
    Keywords: porous carbons ; activation ; oxidation ; surface oxygen groups ; LTPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A styrene/divinylbenzene copolymer has been used as precursor for making porous carbons with bimodal pore size distributions (i.e., with both microporosity and mesoporosity). Pretreatment of the as-received copolymer by mild oxidation in air, significantly increased the carbon yield after carbonization. Reactivity studies of the polymer-based chars to CO2 clearly show the influences of some important factors such as carbonization temperature, heating rate, soak time on char reactivities. Bimodal porous carbons were prepared by carbonization of the preoxidized styrene/divinylbenzene copolymer in N2, followed by activation in CO2 at different temperatures to different levels of burnoff. The pore structures of the porous carbons produced have been characterized by various techniques such as gas adsorption and mercury porosimetry. The surfaces of the porous carbons produced, and a commercial carbon adsorbent, have been modified with HNO3 and H2O2 treatment at various conditions. Characterization of the surface oxygen functionality, both quantitatively and qualitatively, has been achieved using techniques such as Linear Temperature Programed Desorption (LTPD) and selective neutralization of bases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133008
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  • 8
    Electronic Resource
    Electronic Resource
    Activated carbon membrane for water treatments: Application to decolorization of coke furnace wastewater (1997)
    Springer
    Adsorption 3 (1997), S. 93-98 
    Details
    ISSN: 1572-8757
    Keywords: activated carbon ; membrane ; carbon membrane ; water treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An activated carbon membrane to be used in water treatments was developed and the decolorization of the coke furnace wastewater was successfully demonstrated as a model case. The activated carbon membrane was prepared by carbonizing poly-vinydenchloride (PVdC) and poly-vinylalcohol (PVA) microspheres aggregating on and within a ceramic pipe. The membrane developed in this work was suspected to have a bidispersed structure, which made it possible to play the roles of both a porous membrane having the molecular weight cut-off of about 10,000 and an activated carbon bed where the dissolved organics with low molecular weight could be adsorbed. The activated carbon membrane developed in this work appears to be useful for compact water treatment processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133010
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the micropore volume distribution function of activated carbons by gas adsorption (1997)
    Springer
    Adsorption 3 (1997), S. 55-65 
    Details
    ISSN: 1572-8757
    Keywords: activated carbons ; characterization of structure ; equilibrium ; heat of adsorption ; theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A new method for the determination of the micropore volume distribution function of activated carbons is presented. It is based on the treatment of pure gas adsorption isotherms by a theoretical model derived from the Hill-de Boer theory. Adsorption data (isotherms and heat curves) for carbon dioxide, ethane and ethylene on activated carbon (F30/470 CHEMVIRON CARBON) have been provided by a thermobalance coupled to a calorimeter (TG-DSC 111 SETARAM) at different temperatures (233, 273, 303 and 323 K) for pressures up to 100 kPa. Adsorption isotherms of carbon dioxide and ethane at 303 and 323 K have been used for the determination of the micropore volume distribution function of the activated carbon of interest. The knowledge of its structure has then allowed the simulation of adsorption isotherms and heats for the same adsorbates at the same temperatures as those experimentally studied. Similar calculations have been conducted for ethylene. Whatever the adsorbate (carbon dioxide and ethane used for the determination of the micropore volume distribution function or ethylene), the mean deviation between experimental and calculated isotherms does not exceed 4% at quasicritical and supercritical temperatures (303 and 323 K). In the same temperature conditions, discrepancies between calculation and experiment reach about 10% for adsorption heats. For both isotherms and heats, large discrepancies appear at low temperature (233 and 273 K). This method allows the determination of the micropore volume distribution function of activated carbons. The validity of the results is insured using several isotherms of several adsorbates and taking into account the calorimetric effect of the phenomenon. That is the reason why this method can also be seen as a new possible model for pure gas adsorption data prediction. This paper also presents a brief summary of the state of the art in this field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133007
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  • 10
    Electronic Resource
    Electronic Resource
    Fifty years of the theory of the volume filling of micropores (1997)
    Springer
    Adsorption 3 (1997), S. 187-188 
    Details
    ISSN: 1572-8757
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650129
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  • 11
    Electronic Resource
    Electronic Resource
    Theoretical basis for the Dubinin-Radushkevitch (D-R) adsorption isotherm equation (1997)
    Springer
    Adsorption 3 (1997), S. 189-195 
    Details
    ISSN: 1572-8757
    Keywords: Dubinin-Radushkevitch equation ; Dubinin-Astakhov equation ; adsorption ; micropore adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Dubinin-Radushkevitch (D-R) equation, which was originally proposed as an empirical adaptation The Polanyi adsorption potential theory, has been the fundamental equation to quantitatively describe the adsorption gases and vapors by microporous sorbents. The equation, based on the postulate that the mechanism for adsorption in micropores is that of pore-filling rather than layer-by-layer surface coverage, generally applies well to adsorption systems involving only van der Waals forces and is especially useful to describe adsorption on activated ???. The ability of the D-R equation to describe gas adsorption on porous materials has inspired many to undertake studies, both experimental and theoretical, to explain the source of the success of the D-R equation in ??? of molecular properties at the gas-solid interface. In many cases, these studies have led to extensions or modifications of the original D-R equation. Many of these attempts and the resulting extensions are reviewed and discussed here. Recently, an isotherm equation was derived for adsorption of gases and vapors on microporous ??? from statistical mechanical principles. It was shown that the D-R equation is an approximated form of this potential theory isotherm. This development is also reviewed and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650130
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  • 12
    Electronic Resource
    Electronic Resource
    An analytical method of micropore filling of a supercritical gas (1997)
    Springer
    Adsorption 3 (1997), S. 197-208 
    Details
    ISSN: 1572-8757
    Keywords: micropore filling ; supercritical gas ; carbon micropore ; nitrogen monooxide ; methane ; molecular assembly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The supercritical gas adsorbed in the micropore having a strong molecular field was presumed to transform into the quasi-vapor to be filled in the micropore (quasi-vaporization adsorption mechanism). The Dubinin-Radushkevitch (DR) equation for micropore filling of vapor was extended to the quasi-vaporized supercritical gas using the quasi-saturated vapor pressureP 0 q and the inherent micropore volumeW L . The reason why the concepts ofP 0q andW L were introduced was explained with the molecule-pore interaction potential theory which is based on the Lennard-Jones interaction. The extended DR equation was named the supercritical DR equation. TheW L was evaluated by the Langmuir plot of the adsorption isotherm for a supercritical gas and both ofP 0q andW L provided the single reduced adsorption isotherms of supercritical NO, N2, and CH4 on activated carbon fibers and high surface area carbons were analyzed by the supercritical DR plots. The wide applicability of the reduced adsorption isotherm to these adsorption data was explicity shown. The two phase model of the organized and confined fluids was proposed in order to improve the quasi-vaporization adsorption mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650131
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  • 13
    Electronic Resource
    Electronic Resource
    Critical discussion of simple adsorption methods used to evaluate the micropore size distribution (1997)
    Springer
    Adsorption 3 (1997), S. 209-219 
    Details
    ISSN: 1572-8757
    Keywords: carbons ; porous structure ; Horvath-Kawazoe method ; Dubinin-Astakhov equation ; gas adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The well-known simple adsorption methods used to evaluate the micropore size distribution from low pressure adsorption isotherms were examined by employing model isotherms for slit-like graphite micropores obtained from nonlocal density functional theory. It was shown that in the range of pore sizes from about 0.4 to 0.9 nm, the Horvath Kawazoe (HK) method satisfactorily reproduces the shape of the micropore size distribution, but the pore sizes are underestimated. In the case of micropores wider than 0.9 nm, the method fails as the formation of the monolayer on the pore walls produces a peak corresponding to 0.6 nm micropores on the HK pore size distribution. Therefore, the HK method indicates the presence of microporosity even for nonporous samples. The Dubinin-Astakhov adsorption isotherms were also examined and it was shown that their application to represent local adsorption isotherms for homogeneous pores is questionable. However, the adsorption potential distributions seem to be promising for micropore analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650132
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  • 14
    Electronic Resource
    Electronic Resource
    On the porous structure of coals: Evidence for an interconnected but constricted micropore system and implications for coalbed methane recovery (1997)
    Springer
    Adsorption 3 (1997), S. 221-232 
    Details
    ISSN: 1572-8757
    Keywords: coalbed methane ; coal (porous structure, micropores) ; adsorption (of xenon, carbon dioxide, methane) ; Xe-129 NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An experimental and theoretical study of adsorption and diffusion of carbon dioxide and methane in coals of widely varying rank was carried out. Low pressures adsorption isotherms of CO2 were obtained and analyzed using Dubinin's theory of volume filling of micropores. High-pressure adsorption isotherms of CH4 were obtained and analyzed using tracer pulse chromatography in conjunction with an appropriate adsorption/diffusion model. A preliminary129Xe NMR analysis of chemical shifts experienced by xenon atoms in particles of different sizes is also reported. The heretofore undocumented and/or underestimated effects of activated diffusion of CO2 at 273–298 K complicate the elucidation of the true microporous structure of coals, especially its dependence on coal rank. Activated diffusion of both CO2 and methane at room temperature does not allow reliable estimates of coalbed gas content to be made. A model of an interconnected network of pores which includes randomly distributed, numerous and ultramicroporous constrictions (at any size scale) is consistent with all these experimental and theoretical findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650133
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  • 15
    Electronic Resource
    Electronic Resource
    Steam-carbon gasification catalyzed by calcium: Assessment of the porous structure of active carbons from plum stones and synthetic active carbons (1997)
    Springer
    Adsorption 3 (1997), S. 233-242 
    Details
    ISSN: 1572-8757
    Keywords: natural active carbons ; synthetic active carbons ; porous structure ; pore size distribution ; modification of active carbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A need for an elaboration of the methods for synthesis and characterization of activated carbons with a requisite porous structure has existed for a long time. One of the methods giving possibility for creating controlled mesopore and micropore structures deals with the steam gasification of various carbon materials. In this work the effects of calcium catalyst on the catalytic steam gasification of active carbons from plum stones and porous polymers are presented. Determination of micropores capacity and specific adsorption in mesopores have been performed by means of theα s method, but adsorption on the heterogeneous solids was described by the integral equation with various local isotherms. This equation has been solved by the regularization method. Based on this method the changes in structural parameters of active carbons depending on the amount of calcium catalyst were estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01650134
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  • 16
    Electronic Resource
    Electronic Resource
    Equilibria and kinetics characterisation of two different structured nutshell-derived activated carbons (1997)
    Springer
    Adsorption 3 (1997), S. 267-275 
    Details
    ISSN: 1572-8757
    Keywords: characterisation ; equilibria ; kinetics ; micropore size distribution ; n-butane ; nutshell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Adsorption equilibria and dynamics ofn-butane on two activated carbon samples prepared from the physical activation of nutshell are studied in this paper. The micropore size distribution (MPSD) is considered as the main source of solid heterogeneity. Lennard-Jones' potential theory and Dubinin's theory (TVFM) are used in the equilibria data to derive the MPSD, which is well fitted by a Gamma distribution function. The adsorption energy distribution derived from the MPSD is very asymmetric for both the samples studied, and this energy distribution used in the HMSD/HMSMD kinetics models for the study of adsorption dynamics ofn-butane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01653629
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  • 17
    Electronic Resource
    Electronic Resource
    Adsorption of normal and branched paraffins in faujasite zeolites NaY, HY, Pt/NaY and USY (1997)
    Springer
    Adsorption 3 (1997), S. 251-265 
    Details
    ISSN: 1572-8757
    Keywords: multicomponent equilibrium ; zeolite ; chromatography ; paraffins ; heat of adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of chain length and branching of paraffins (from C6 to C12) on adsorption and diffusion in zeolites NaY, Pt/NaY, HY and USY has been investigated using the chromatographic method at 275–400°C. The Henry constants of the paraffins increase exponentially with the chain length (with a factor two per extra carbon group), the heats of adsorption increase with circa 7 kJ/mol per extra carbon group. Multicomponent sorption experiments reveal that longer chains are adsorbed preferentially over shorter chains, even at higher loadings. The multicomponent adsorption can be reasonably well described by an extended Langmuir adsorption isotherm, in which the stronger adsorption of the longer chains is reflected by their higher Henry constants. The molecular shape and zeolite type within this FAU group has only a small influence on the adsorption properties. Mass transfer in the pellets as used in catalytic conditions seems to be limited by macropore diffusion, rather than by micropore diffusion, which cannot be measured with the chromatographic method. Increasing the Si/Al-ratio of the zeolite reduces the adsorption capacity, but does not influence the relative adsorption properties.
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    URL: http://dx.doi.org/10.1007/BF01653628
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  • 18
    Electronic Resource
    Electronic Resource
    Influence of analysis conditions on low pressure adsorption measurements and its consequences in characterization of energetic and structural heterogeneity of microporous carbons (1997)
    Springer
    Adsorption 3 (1997), S. 277-282 
    Details
    ISSN: 1572-8757
    Keywords: surface heterogeneity ; nitrogen adsorption ; micropore analysis ; microporous carbon ; low pressure adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Nitrogen adsorption isotherms on nonporous and microporous carbons were thoroughly studied at low relative pressures. For nonporous carbons low pressure measurements seem to be unaffected by analysis conditions. However, these measurements on microporous solids may be affected by analysis conditions at relative pressures below 10−4. It was shown that selection of proper equilibration time is crucial for correct measurements of equilibrium pressures during adsorption on microporous carbons. The isotherm shift induced by insufficient equilibration of the system may affect the surface heterogeneity and microporosity analysis. A comparison of the adsorption energy and pore volume distribution functions calculated from low pressure nitrogen adsorption isotherms measured at different equilibration times on a microporous carbon shows that this effect is smaller than it was expected.
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    URL: http://dx.doi.org/10.1007/BF01653630
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  • 19
    Electronic Resource
    Electronic Resource
    Review of time lag permeation technique as a method for characterisation of porous media and membranes (1997)
    Springer
    Adsorption 3 (1997), S. 283-312 
    Details
    ISSN: 1572-8757
    Keywords: time lag ; porous media ; membrane ; Frisch's method ; permeation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The time lag permeation technique has proven to bean effective method for characterisation. Because of the simple nature of the permeation experiment, transport parameters can be directly obtained from experimental data hence avoiding the intensive mathematical treatment required by other techniques. The method has historically been applied to diffusion and adsorption in porous membranes and diffusion in polymer membranes. Since its origins in 1920, interest in the time lag method has expanded because of its value in characterising simple permeation processes and also complex systems of diffusion with simultaneous adsorption and surface diffusion. This review focuses on presenting the asymptotic solution of the mass balance diffusion equations and includes applications of time lag analysis, in order to give a critical and broad perspective of this method as a tool for characterisation. It includes much of the previously published literature in order to show that for most cases the asymptotic solution of the transport equations is simple, and for more complex cases that an analytical solution is possible hence avoiding cumbersome numerical techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01653631
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  • 20
    Electronic Resource
    Electronic Resource
    Synthesis of alternatingly 6-O-methylated cellulose via enzymatic polymerization of a substituted cellobiosyl fluoride monomer catalyzed by cellulase (1997)
    Springer
    Cellulose 4 (1997), S. 161-172 
    Details
    ISSN: 1572-882X
    Keywords: alternatingly 6-O-methylatedcellulose ; enzymatic polymerization ; cellulase ; 6-O-methyl-β-cellobiosyl fluoride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Novel cellobiose derivatives, 6-O-methyl, 6′-O-methyl, 6,6′-di-O-methyl- β-cellobiosyl fluorides, have been prepared and their hydrolytic behaviour as well as polymerizability by a purified cellulase from Trichoderma viride were investigated. Among these compounds, 6-O-methyl-β-cellobiosyl fluoride was found to polymerize by the cellulase catalysis in a mixed solvent of acetonitrile and acetate buffer (pH 5.0), giving rise to an alternatingly 6-O-methylated cellulose derivative. The stereoselective formation of the β(1 ← 4) glycosidic bond is explained by a mechanism involving double inversion at the C1 carbon of the substrate. Another cellobiose derivative, 6′O-methyl-β-cellobiosyl fluoride, gave a mixture of low molecular weight oligomers. The difference in the observed polymerizability was explained by assuming a difference in steric repulsions between the methyl groups and an amino acid residue at the enzyme catalytic site
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    Crystalline forms of cellulose in the silver tree fern Cyathea dealbata (1997)
    Springer
    Cellulose 4 (1997), S. 269-279 
    Details
    ISSN: 1572-882X
    Keywords: nuclear magnetic resonance ; cellulose Ialpha ; cellulose Ibeta ; fern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Solid-state 13C NMR spectroscopy was used to characterize fibrous material cut from the midrib of a fern frond. Signals associated with cellulose crystallites were separated from those associated with the lignin--hemicellulosic matrix by exploiting differences in proton rotating-frame relaxation time constants. Heights of signals at 90.2 and 88.5 ppm, assigned to C-4 in cellulose Iα and Iβ, indicated similar proportions of the two crystalline forms. This observation conflicts with a suggestion that plant celluloses can be grouped into the two categories of Iα-rich and Iβ-rich.
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    The effect of Trichoderma reesei cellulases and hemicellulases on the paper technical properties of never-dried bleached kraft pulp (1997)
    Springer
    Cellulose 4 (1997), S. 329-339 
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    ISSN: 1572-882X
    Keywords: cellulases ; hemicellulases ; kraft pulp ; properties ; refining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Four purified cellulases, a xylanase and mannanase from Trichoderma reesei were used to treat never-dried bleached pine kraft pulp prior to refining, and the effects on pulp properties were evaluated. The enzymatic treatments hydrolysed up to 0.8% of pulp dry weight. The results demonstrated that the individual cellulases have profoundly different modes of action in modifying pulp carbohydrates. This is especially clear when comparing their effects at the same level of hydrolysis. Pretreatment with cellobiohydrolases I (CBH I) and II (CBH II) had virtually no effect on the development of pulp properties during refining, except for a slight decrease in strength properties. On the contrary, endoglucanase I (EG I) and endoglucanase II (EG II) improved the beatability of the pulp as measured by Schopper--Riegler value, sheet density and Gurley air resistance. Of the endoglucanases, EG II was most effective in improving the beating response. The combinations of CBH I with EG I and EG II had similar effects on the pulp properties as the endoglucanases alone, although the amount of hydrolysed cellulose was increased. Pretreatments with xylanase or mannanase did not appear to modify the pulp properties. The same enzyme treatments which improved the beatability, however, slightly impaired the pulp strength, especially tear index at the enzyme dosages used. When compared at a given level of cellulose hydrolysis, the negative effect of EG II on strength properties was more pronounced compared with EG I. Thus, the exploitation of cellulases for fibre treatments requires careful optimization of both enzyme composition and dosage. Since the endoglucanases had no positive effect on the development of tensile strength, it is suggested that the explanation for the increased beating response is increased fibre breakage and formation of fines, rather than improved flexibilization.
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    Benzylated pulps from sugar cane bagasse (1997)
    Springer
    Cellulose 4 (1997), S. 21-31 
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    ISSN: 1572-882X
    Keywords: bagasse pulp ; benzylation ; Tg ; cellulosicthermoplastics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An optimized ethanol/water process has been employed for the pulping of fibres from sugar cane bagasse. After pretreatment with aqueous NaOH, unbleached pulps were subjected to benzylation at 110 °C for different periods of time. The resulting purified products were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and infrared spectroscopy (IR). The results showed that benzylation proceeded to various extents depending on the reaction time, as assessed by weight gain. During the first 3 h, a loss of mass was observed due to the occurrence of benzylation of low molecular weight polyoses, which were eliminated in the purification step. After that period of time a drastic weight increase was observed probably because crystalline regions had developed. The samples with low degrees of benzylation were insoluble, whereas the more benzylated counterparts showed limited solubility in THF. Partially soluble samples and a completely soluble one showed very different GPC elution profiles. This may be attributed to the efficiency of the pre treatment which, in the latter case, employed more concentrated alkali. Thermogravimetric analyses showed that all samples were degraded above 310 °C. Glass transition temperatures ranged between 42 °C and 65 °C, increasing as the extent of benzylation increased
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    Some microrheological aspects of wood-pulp fibres subjected to fatigue loading (1997)
    Springer
    Cellulose 4 (1997), S. 51-56 
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    ISSN: 1572-882X
    Keywords: fibre ; fatigue ; damage accumulation ; microstructuraldegradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Wood-pulp fibres are recognized as concentrically-layered, laminated composite tubes of structural reinforcing material, the cellulose microfibrils, embedded in a cementing matrix of hemicellulose and lignin. When the single fibres are subjected to cyclic mechanical action, their morphological behaviour is characterized by the fatigue growth of micro-voids and surface damage which individually and collectively give rise to stress concentrations, and eventually crack development. The progressive damage phenomena, evinced by the surface imaging and optical sectioning techniques through utilizing confocal laser scanning microscopy, are understood to be consequences of the cumulative material micromechanical degradation and subsequent microstructural breakdown of the cellulose microfibrillar framework. This structural breakdown is believed to effect the fibrillation and flexibilization of the fibres
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    Identification of cellulose synthase(s) in higher plants: sequence analysis of processive β-glycosyltransferases with the common motif ’D, D, D35Q(R,Q)XRW‘ (1997)
    Springer
    Cellulose 4 (1997), S. 33-49 
    Details
    ISSN: 1572-882X
    Keywords: β-Glycosyltransferases ; Acetobacter xylinum ; cellulosesynthase ; higher plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract More than ten β-glycosyltransferases are now recognized that have limited similarity to the amino acid sequence of cellulose synthase from Acetobacter xylinum. Using hydrophobic cluster analysis (HCA), we recently identified two domains and putative catalytic residues in the processive β-glycosyltransferases. In this study, we have found expressed sequence tags (ESTs) from higher plants (Arabidopsis thaliana, Brassica campestris, and Oryza sativa) that exhibit a limited sequence similarity to the A. xylinum cellulose synthase. These ESTs contain some of the conserved residues identified in the processive β-glycosyltransferases. Complete sequencing of an EST clone (T88271) from A. thaliana led to the identification of all the conserved residues in the derived truncated polypeptide which appears to be part of a putative cellulose synthase. Sequence comparison of proteins with known function and several unidentified proteins have the ‘D, D, D35Q(R,Q)XRW’ motif which is considered a strong predictor for β-glycosyltransferasesthat includes, among other proteins, cellulose and chitin synthases. The first two conserved aspartic acid residues in this motif were analysed by site-directed mutagenesis, and their replacement by another amino acid led to a loss of cellulose synthase activity in A. xylinum, suggesting that they are essential for enzyme activity. A correlation between the second residue (R or Q) in the Q(R,Q)XRW sequence and the synthesis of along glucan chain (polysaccharide) or a short glucan chain(oligosaccharide) suggests that this residue may be involved in the degree of processivity
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    On the kinetics of degradation of cellulose (1997)
    Springer
    Cellulose 4 (1997), S. 1-5 
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    ISSN: 1572-882X
    Keywords: paper ; degradation ; ageing ; kinetics ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1023/A:1018408515574
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    Mercerization and acid hydrolysis of bacterial cellulose (1997)
    Springer
    Cellulose 4 (1997), S. 75-87 
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    ISSN: 1572-882X
    Keywords: bacteria, cotton linter ; mercerization ; acidhydrolysis ; leveling-off degree of polymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Structural changes in never- dried, disintegrated bacteria l cellulose by treatment with aqueous NaOH were examined by electron microscopy, X-ray diffractometry and acid hydrolysis behaviour and compared with those of cotton cellulose. The microfibril kept its fibrillar morphology after treatment with NaOH solutions of less than 9% (w/w), but changed into irregular aggregates when treated with NaOH above 12% (w/w), corresponding to the crystal conversion to cellulose II. The crystallinity of the resulting cellulose II was very low after a brief alkali treatment, but was increased significantly by elongated treatment (up to 10 days). In contrast, cotton cellulose was converted to cellulose II of fairly high crystallinity by alkali treatment of as little as 3 min duration, and the crystallinity did not change with longer treatments. The leveling-off degree of polymerization (LODP) of bacterial cellulose was decreased from 150 to 50 by 18% (w/w) NaOH treatment, while that of cotton linter decreased from 260 to 70. These characteristic differences between cotton linter cellulose and bacterial cellulose can be ascribed to a basic difference in microfibrillar organization in these materials: the microfibrils in cotton cellulose are in close contact with neighbouring microfibrils having opposite polarity, and in bacterial cellulose are isolated from each other and require chain folding to form the antiparallel cellulose II crystal
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    NMR analysis of cellulose dissolved in aqueous NaOH solutions (1997)
    Springer
    Cellulose 4 (1997), S. 99-107 
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    ISSN: 1572-882X
    Keywords: sodium hydroxide ; mercerization ; NMR ; chemical shift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Low molecular weight cellulose (degree of polymerization = ca 15) was dissolved in 4-- 30% NaOD/D2O, and relationships between 1H- and 13C-chemical shifts of the cellulose and NaOD concentrations were studied in terms of the dissociation of three hydroxyl groups of cellulose in aqueous NaOH solutions. All C---H proton resonances were shifted upfield linearly with an increase in the NaOD concentration, indicating that all C---H protons of cellulose undergo the electron-shielding effect by NaOH. On the other hand, the shifting patterns of carbon resonances varied among the six carbons: C1 and C4 carbons undergo the electron-shielding effect, whereas C2, C3, C5, and C6 carbons experience the electron-deshielding effect by NaOH. Changes in 13C-chemical shifts of cellulose carbons in 4--30% NaOD/D2O indicate that C3---OH has the highest resistance to dissociation in aqueous NaOH of the three hydroxyl groups of an anhydroglucose residue. It is plausible, at least from the aspects of 13C-chemical shifts, that cellulose molecules dissolving in 20--30% NaOH behave differently from those swollen in 20--30% NaOH as alkali- cellulose
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    Preparation and properties of a new type of comb-shaped, amphiphilic cellulose derivative (1997)
    Springer
    Cellulose 4 (1997), S. 89-98 
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    ISSN: 1572-882X
    Keywords: O-(2-hydroxy-3-butoxyp ropyl) cellulose ; comb-shaped polymer ; amphiphilic cellulose derivative ; sol-geltransition ; micellization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Comb-shaped, amphiphilic O-(2- hydroxy-3-butoxypropyl) cellulose (HBPC) was prepared by a homogeneous reaction of cellulose with butyl glycidyl ether (BGE) in a 10% (w/w) LiCl--DMAc solution. It was found that: (a) the molar substitution (MS) of water-soluble HBPC ranges from 0.4 to 1.0, and is nearly equal to its degree of substitution (DS), indicating that the HBPC derivatives obtained are comb-shaped polymers; (b) the water-soluble HBPC shows a thermally reversible sol-gel transition in aqueous solution; and (c) the derivative having a DS of 0.6 shows surface activity with critical micelle concentration (cmc) in the order of 0.8 g/l and surface tension of 31.5 dyn/cm
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    The assignment of IR absorption bands due to free hydroxyl groups in cellulose (1997)
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    Cellulose 4 (1997), S. 281-292 
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    ISSN: 1572-882X
    Keywords: FTIR ; free hydroxyl groups ; curve fitting ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Interpretation of the IR hydroxyl absorption bands in cellulose has been limited to the inter- and intramolecularly hydrogen-bonded hydroxyl groups in the crystalline form. This paper attempts to assign IR frequencies due to ‘free‘ or non-hydrogen bonded hydroxyl groups by using a curve fitting method. The almost completely methylated cellulose derivatives of tritylcellulose (previously used in related studies) exhibited small IR bands due to hydroxyl groups. The IR bands were assumed to appear under stereohindered conditions and thus resulted in a mixture of bands which included the contribution of free hydroxyl groups. The curve fitting method deconvoluted the IR bands into three bands in the OH stretching region: they were interpreted in terms of free or hydrogen bonded hydroxyl groups. The assignments were confirmed by comparison of an almost completely methylated derivative with partially methylated derivatives having different degrees of substitution. In addition, intramolecular hydrogen bonds involving OH at the C-3, C-2 and C-6 positions were shown to be easily formed, even between extremely small numbers of unsubstituted hydroxyl groups present, and thus cause perturbation of the specific deconvoluted band.
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    An ultrastructural study of the interaction of a fungal endoglucanase from Humicola insolens with cotton fibres (1997)
    Springer
    Cellulose 4 (1997), S. 7-20 
    Details
    ISSN: 1572-882X
    Keywords: cellulase ; cottonfibres ; electron microscopy ; biopolishing ; adsorption ; colloidalgold labeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Because cellulases are finding more applications in the textile and detergent industries, their effect on cotton fibres must be evaluated. For this purpose, the action of a recombinant cellulase, endoglucanase V from the fungus Humicola insolens, has been followed by scanning electron microscopy (SEM) in classical longitudinal views as well as in cross-sections of cotton fibres. The experiments were conducted at large enzyme dilution typical of conditions where cellulases are used for biopolishing, i.e. for the removal of defects created by mechanical abrasion. Endoglucanase V appears to restrict its action to the hydrolysis of the loose fibrils created at the surface of the fibres and no indication of extensive enzyme penetration and damage to the interior of the fibres could be detected by SEM. The adsorption sites for endoglucanase V on cotton fibres were examined by transmission electron microscopy (TEM) on ultrathin cross-sections after immuno-gold labeling of the enzyme. This approach showed that the enzymes did not penetrate the fibres but remained at their surface. The use of an immuno-gold labeled cellulase provides a new way to probe the surface features of cotton fibres
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    Synchrotron-radiated X-ray and neutron diffraction study of native cellulose (1997)
    Springer
    Cellulose 4 (1997), S. 221-232 
    Details
    ISSN: 1572-882X
    Keywords: two crystalline phase system ; synchrotron radiated X-ray diffraction ; time-of-flight neutron diffraction ; cellulose Iα ; cellulose Iβ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Precise determination of d-spacings and compositional ratio of cellulose Iα and Iβ in various native cellulose samples was successfully carried out by synchrotron-radiated X-ray diffraction and time-of-flight (TOF) neutron diffraction from quasi-powder specimens. X-ray diffraction peaks were separated by the deconvolution method using six types of profile function: Gaussian, Lorentzian, intermediate Lorentzian, modified Lorentzian, pseudo-Voigt, and Pearson VII. In terms of R-factors, the pseudo-Voigt function gave the best fit with the observation, and was used for determination of d-spacings. The numerical results for Valonia cellulose were: dIα (1 0 0) = 0.613 nm; dIβ (1 1 0) = 0.603 nm; dIβ (1 1 0) = 0.535 nm; dIα (0 1 0) = 0.529 nm; Iα content = 0.65. The differences determined between dIα (1 0 0) and dIβ (1 1 0) and between dIβ (1 1 0) and dIα (0 1 0) were similar to those previously reported. Comparison between unresolved peaks for the two types of cellulose samples revealed a small but definite difference between dIα (1 1 0) and dIβ (2 0 0). The TOF neutron diffractometry using deuterated samples confirmed this difference.
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    COMMUNICATION: Culture conditions producing structure entities composed of Cellulose I and II in bacterial cellulose (1997)
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    Cellulose 4 (1997), S. 239-245 
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    ISSN: 1572-882X
    Keywords: Acetobacter xylinum ; smooth colony ; rough colony
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Culture conditions for the production of Cellulose I and/or II structures have been investigated by transmission electron microscopy using smooth colonies of Acetobacter xylinum ATCC23769. Cells prepared from smooth colonies produce the band material composed of Cellulose II in phosphate buffer (pH 7) at 4 °C. In contrast, the same cells produce the normal twisting ribbons of Cellulose I when the incubation temperature is raised to 28 °C. The band material is also produced at 4 °C in 2% buffered glucose solution and in the standard Hestrin-Schramm medium.
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    COMMUNICATION: Mild reaction of ethyl cellulose and N- phenylmaleamic acid in acetic anhydride (1997)
    Springer
    Cellulose 4 (1997), S. 233-238 
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    ISSN: 1572-882X
    Keywords: ethyl cellulose ; maleanilic acid ; N-phenylmaleamic acid ; Michael addition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The reaction at room temperature of ethyl cellulose (EC) and N-phenylmaleamic acid (NPMA) (maleanilic acid) in acetic anhydride with a catalytic amount of anhydrous sodium acetate resulted in a Michael type of product whereby a cellulose ether was formed. The cyclisation product N-phenylmaleimide was minor.
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    COMMUNICATION: New derivatives of ethyl cellulose (1997)
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    Cellulose 4 (1997), S. 247-253 
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    ISSN: 1572-882X
    Keywords: ethyl cellulose ; hydroxyethylphthalimide ; carboxymethylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Triethylamine-mediated carboxymethylation of ethyl cellulose using monochloroacetic acid produced a hydroxymethyl acetate derivative (I). The derivative (I) was subsequently converted to a phthalimidoethyl-ethyl cellulose ether derivative by reacting it with β-hydroxyethyl phthalimide using concentrated sulphuric acid as the catalyst. The elemental analysis agreed with the calculated values using an anhydroglucose unit formula that incorporates the degree of substitution. Mechanisms for the formation of these derivatives are proposed.
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    Chemical synthesis of cellulose derivatives by a convergent synthetic method and several of their properties (1997)
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    Cellulose 4 (1997), S. 109-130 
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    ISSN: 1572-882X
    Keywords: cellulose-homologous series ; chemical synthesis ; gelpermeati on chromatography ; molecular rotation ; regio-selectivelysubstituted cellulose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two homologous series of regio- selectively sub stituted cellulose: 3-O-benzyl-2, 6-di-O-pivaloyl derivatives (Series 1) and 2,3,6-tri-O-acetyl derivatives (Series 2) up to an eicosamer (DP = 20), were synthesized for the first time by elongation of the carbohydrate chain from cellooctaose derivative 5 and subsequent deprotection. Some changing properties of the homologous series with increasing DP were examined. Gel permeation chromatography (GPC) analysis for series 1 and 2 indicated that plots of log M vs retention time gave a straight line. The plots of [M]n/n vs (n − 1)/n (where [M]n is the molecular rotation for an oligomer with DP = n) up to a hexadecamer 9 in series 2 gave straight lines, although the result for the eicosamer 11 deviated somewhat from the line
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    Blends of poly(∈-caprolactone) with cellulose alkyl esters: effect of the alkyl side-chain length and degree of substitu tion on miscibility (1997)
    Springer
    Cellulose 4 (1997), S. 131-145 
    Details
    ISSN: 1572-882X
    Keywords: cellulose alkyl esters ; poly(∈-caprolactone) ; blends ; miscibility ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulose alkyl esters, CELL- OCOCnH2n+1(n = 1 ∼ 6), were synthesized by a homogeneous reaction of cotton cellulose with different acyl chlorides in N,N-dimethylacetamide--lithium chloride solution. The miscibility of the esterified celluloses with poly(∈-caprolactone) (PCL) was investigated, mainly through thermal analysis by differential scanning calorimetry (DSC). A polymer pair, cellulose butyrate (CB)/PCL, showed the highest miscibility of all the binary blends examined here; this is usual when relatively high-substituted esters (DS ≥ 2.0) are used as the respective component. The butyl ester derivatives with DS ≤ 1.5 showed poor miscibility with PCL
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    Cellulose: the structure slowly unravels (1997)
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    Cellulose 4 (1997), S. 173-207 
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    ISSN: 1572-882X
    Keywords: structure ; computer ; model ; polymorphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This article attempts to bring together basic and complex information which has been gathered on cellulose structure, principally that of native cellulose, over the last few decades. Even though advances have been made in the field of crystallography, powder crystallography cannot yield a definitive cellulose structure and single crystal diffraction is not possible due to the lack of suitable crystals. Knowledge obtained on the biosynthesis of native cellulose and on the polymorphy of cellulose and its derivatives help our understanding of ultrastructure. Many inconsistencies between early crystallographic studies of native cellulose have been clarified by the discovery that two polymorphs (α and β) of cellulose I exist. Models of the possible ultrastructural arrangements within native cellulose have been put forward over the decades; with advancement in technology, computer simulations of small and large systems are being created to test the viability of these ultrastructural models. It is hoped that this review will aid in the understanding of the complexity and uncertainties that still exist in this subject.
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    Systematic survey on crystalline features of algal celluloses (1997)
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    Cellulose 4 (1997), S. 147-160 
    Details
    ISSN: 1572-882X
    Keywords: algal cellulose ; celluloseIα/Iβ ; triclinic/monoclinic unit cells ; uniplanarorientation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Algal cellulose from different origins has been analysed with special reference to the crystalline features, such as allomorphism (Iα/Iβ or triclinic/monoclinic two- phase model), dimension and uniplanar orientation behaviour of the specific crystallographic plane to the cell wall surface. Three types of cellulose were identified in the algal system: Iα-rich/broad microfibril/0.6 nm-oriented type; Iβ- dominant/flat-ribbon/0.53 nm-oriented type; and Iβ- dominant/small/random-oriented type. The first type appears to occur in more primitive organisms than the other types. The three types of algal cellulose correlate well with the arrangements of cellulose synthesizing complexes, i.e. multiple-row linear type, consolidated rosette type, and isolated rosette type, respectively. In Chara two types of crystals were found: an Iβ-dominant/ribbon shaped/0.6 nm-oriented type and an Iβ/narrow/random-oriented type. The former type, known to occur in some families of tunicates, was first identified in algal cellulose during this study. Reducing-end staining was successfully applied to microcrystal cellulose samples of Cladophorales and Zygnematales, showing that the cellulose microfibril has a parallel-chain structure for both cellulose Iα and cellulose Iβ
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    Atomic force microscopy and transmission electron microscopy of cellulose from Micrasterias denticulata; evidence for a chiral helical microfibril twist (1997)
    Springer
    Cellulose 4 (1997), S. 209-220 
    Details
    ISSN: 1572-882X
    Keywords: atomic force microscopy ; transmission electron microscopy ; microfibril twist
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Atomic force microscopy (AFM), tapping mode atomic force microscopy (TM-AFM) and transmission electron microscopy (TEM) have been used to image the cell wall, ultrathin sections of whole cells and cellulose microfibrils prepared from the green alga Micrasterias denticulata. Measurements of the microfibril dimensions are in agreement with earlier observations carried out by electron microscopy. Images at the molecular level of the surface of the microfibrils were obtained with AFM and show regular periodicities along the microfibril axis that correspond to the fibre and glucose repeat distances of cellulose. Twisted regions visible at intervals along the microfibrils dried down onto substrates were noted to be right-handed in over 100 observations by TEM, AFM and TM-AFM.
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  • 41
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    Spin-lattice relaxation behaviour of water in cellulose materials in relation to the tablet forming ability of microcrystalline cellulose particles (1997)
    Springer
    Cellulose 4 (1997), S. 57-73 
    Details
    ISSN: 1572-882X
    Keywords: microcrystalline cellulose ; tablet ; water ; spin- lattice relaxation time ; spin-spin relaxation time ; NMR ; microfibril
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Medical tablet forming ability of microcrystalline cellulose (MCC) was investigated in relation to the mobility of water molecules in MCC particles. For this purpose, the spin-lattice relaxation time T1 of water in the system was measured by 1H-NMR. Over a wide range of water contents (0.02 ≤ H2O/cellulose (g/g) ≤ 1.79), two different T1 (T1,l and T1,s) values were observed for water in each MCC sample. Below the equilibrium water content, water having these two different T1 values exchange with each other in an MCC particle reaching an equilibrium state within a given time scale (equilibrium constant K). The T1,l, T1,s and K values for water in MCC, estimated at the equilibrium water content, showed fairly good correlations with the hardness of the tablets made by the MCC samples. Sample with a shorter T1, or larger K tended to have a stronger tablet forming ability. In the spin-spin relaxation time T2 measurements for protons in an MCC/D2O system, two T2 components originating from the glassy cellulose solid (T2,G) and the swelling region (T2,l) were observed. It was found that the mole fraction xL of protons with T2,L in the system exhibits a clear linear correlation with K. From these results, a structural model for the distribution of water in MCC particles was propoed by taking the surface of each microfibril and the disordered region within the microfibril into consideration
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    Adsorption of a Trichoderma reesei endoglucanase and cellobiohydrolase onto bleached Kraft fibres (1997)
    Springer
    Cellulose 4 (1997), S. 255-268 
    Details
    ISSN: 1572-882X
    Keywords: biotechnology ; cellulase ; endoglucanase ; cellobiohydrolase ; adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Cellulases can be used to modify pulp fibres. For the development of biotechnical applications, a better understanding of the adsorption of cellulases onto commercial wood fibres is needed. In this work, the adsorption behaviour of purified CBH I and EG II on bleached Kraft fibres was investigated. Three variables were studied with respect to their effect on adsorption: fibre type (hardwood or softwood), fibre history (never-dried or once-dried), and ionic strength. The results showed that fibre history had the largest influence on the extent of adsorption of each enzyme. The effect of ionic strength was shown to be dependent on the enzyme and fibre type. At high ionic strength, CBH I exhibited a higher affinity for both once-dried and never-dried fibres at low enzyme concentrations; however, salt was shown to decrease the extent of adsorption at higher enzyme dosages. In contrast, salt increased the maximum adsorption of EG II, most notably on the once-dried hardwood fibres. Fibre type was also shown to affect adsorption behaviour. CBH I had a higher affinity for softwood fibres than for hardwood fibres at low enzyme concentrations. The maximum adsorption of EG II onto once-dried softwood fibres increased by 80% compared to the once-dried hardwood fibres. Interestingly, this did not correlate to in creased fibre hydrolysis.
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    Effect of substituent distribution on water solubility of O-methylcellulose (1997)
    Springer
    Cellulose 4 (1997), S. 321-327 
    Details
    ISSN: 1572-882X
    Keywords: O-methylcellulose ; water solubility ; substituents distribution ; regioselective substitution ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of substituent distribution on the water solubility of O-methylcellulose (MC) was re-examined to elucidate the lower limit of the degree of substitution (DS) in water-soluble MC. To this end, a series of 2,3-MCs which are regioselectively substituted at the C-2 and C-3 hydroxyl groups were prepared by homogeneous methylation. It was found that the lower limit for the DS value of water-soluble 2,3-MC was almost the same as that for MCs having even distributions of substituents along the cellulose chain as well as in the anhydroglucose units.
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    The surface chemical modification of cellulosic fibres in view of their use in composite materials (1997)
    Springer
    Cellulose 4 (1997), S. 305-320 
    Details
    ISSN: 1572-882X
    Keywords: surface modification ; oligomeric reagents ; polymeric reagents ; anhydrides ; isocyanates ; Fourier-transform Infrared Spectroscopy ; elemental analyses ; scanning electron microscopy ; X-ray photoelectron spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The surface modification of various cellulosic materials was studied in heterogeneous conditions using different grafting agents bearing anhydride or isocyanate reactive groups. Some of these reagents were oligomeric, others polymeric and most were chosen so as to provide a non-polar character to the surface of the fibres in view of their possible use as reinforcing agents in composites based on polymeric matrices. The success of these chemical modifications was assessed by Fourier-transform Infrared Spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and elemental analysis. The accessibility of the superficial OH groups varied as a function of the coupling agent in terms of both molecular size and chemical nature and ranged between 1 and 3% of the total hydroxy groups borne by the initial cellulose sample.
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    Swelling of carboxymethylated cellulose fibres (1997)
    Springer
    Cellulose 4 (1997), S. 293-303 
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    ISSN: 1572-882X
    Keywords: carboxymethylcellulose ; acid groups ; water retention ; swelling ; hornification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Swelling of cotton cellulose fibres having different proportions of carboxyl groups in the H-form was studied. The carboxyl groups were introduced by carboxymethylation under different reaction conditions. By studying the swelling of modified cellulose samples (water retention value of non-dried fibre) it was shown that the concentration of sodium hydroxide was the dominant factor among the investigated reaction parameters. The number of acidic groups was found to play a significant but not determinative role in the level of improvement in swelling caused by carboxymethylation. A linear correlation was observed between swelling and iodine sorption capacity. The degree of collapse of the highly accessible structure of cellulose during drying (hornification) was larger in the case of more accessible carboxymethylated fibres than for the alkali treated sample. The degree of hornification increased with growing swellability and with growing number of carboxyl groups in the investigated interval (40–120 mmol carboxyl/mol cellulose). This type of modified cellulosic fibre could be used for enhanced entrapping and release of chemicals.
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    Electrochemical disinfection of drinking water using an activated-carbon-fiber reactor capable of monitoring its microbial fouling (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 18-22 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An electrochemical reactor employing activated carbon fibers (ACF) was constructed for the disinfection of bacteria in drinking water. The application of an alternating potential of 1.0 V and −0.8 V versus a saturated calomel electrode, for disinfecting and desorbing bacteria, enabled reactor operation for 840 h. Drinking water was passed through the reactor in stop/flow mode: 300 ml/min flow for 12 h and no flow for 12 h, alternately. The bacterial cell density in treated water was always been less than 20 cells/ml. It was also found that the formation of biofilm on the ACF reactor caused an increase in current, enabling the self-detection of microbial fouling.
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    Production of synthetic spider dragline silk protein in Pichia pastoris (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 33-39 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The methylotrophic yeast Pichia pastoris was tested as a host for the production of long, repetitive protein polymers. Synthetic genes for a designed analog of a spider dragline silk protein were readily expressed at high levels under control of the methanol-inducible AOX1 promoter. Transformants containing multiple gene copies produced elevated levels of silk protein, but of a variety of altered sizes as a result of gene rearrangements at the time of transformation. Genes up to 3000 codons in length or longer could be expressed with no evidence of the prevalent truncated synthesis observed for similar genes in Escherichia coli, though genes longer than 1600 codons were expressed less efficiently than shorter genes. Silk-producing P. pastoris strains were stable without selection for at least 100 doublings.
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    Application of the polymerase chain reaction (PCR) and reverse transcriptase / PCR for determining the fate of phenol-degrading Pseudomonas putida ATCC 11172 in a bioaugmented sequencing batch reactor (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 236-240 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The impact of bioaugmentation on the efficacy of an existing microbial population to detoxify phenol in a laboratory-scale sequencing batch reactor was evaluated. Phenol degradation and the persistence and expression of the catabolic dmpN gene were studied for 44 days using a combination of conventional monitoring approaches and molecular techniques. Following addition of the phenol-degrading bacterium, Pseudomonas putida ATCC 11172, which converts phenol to catechol by the aerobic meta-cleavage pathway, phenol removal␣in the bioaugmented reactor increased and was maintained at 95 %–100 %. In the unaugmented control reactor, decreased phenol removal was observed. Correspondingly, dmpN DNA, characteristic of P. putida ATCC 11172, and its expression were detected in activated sludge biomass from the bioaugmented reactor for over 41 days. The results of this study show that (i) bioaugmentation provides stability in phenol degradation, and (ii) monitoring with molecular techniques such as the polymerase chain reaction (PCR) and reverse transcriptase/PCR can successfully assess the state of a bacterium used in bioaugmentation.
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    Cloning of the Bacillus pumilusβ-xylosidase gene (xynB ) and its expression in Saccharomyces cerevisiae (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 262-266 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A genomic DNA library of the bacterium Bacillus pumilus PLS was constructed and the β-xylosidase gene (xynB) was amplified from a 3-kb genomic DNA fragment with the aid of the polymerase chain reaction technique. The amplified xynB gene was inserted between the yeast alcohol dehydrogenase II gene promoter (ADH2 P ) and terminator (ADH2 T ) sequences on a multicopy episomal plasmid (pDLG11). The xynB gene was also fused in-frame to the secretion signal sequence of the yeast mating pheromone α-factor (MFα1 S ) before insertion between the ADH2 P and ADH2 T sequences on a similar multicopy episomal plasmid (pDLG12). The resulting construct ADH2 P -MFα1 S -xynB-ADH2 T was designated XLO1. Both plasmids pDLG11 and pDLG12 were introduced into Saccharomyces cerevisiae but only the expression of the XLO1 gene yielded biologically functional β-xylosidase. The total β-xylosidase activity remained cell-associated with a maximum activity of 0.09 nkat/ml obtained when the recombinant S. cerevisiae strain was grown for 143 h in synthetic medium. The temperature and pH optima of the recombinant Xlo1 enzyme were 45–50 °C and pH 6.6 respectively. The enzyme was thermostable at 45 °C; however, at 60 °C most of the Xlo1 was inactive after 5 min.
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    Inhibition of mesophilic solid-substrate anaerobic digestion by ammonia nitrogen (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 284-291 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This work focused on determining the effects of ammonia-nitrogen supplementation on the mesophilic solid-substrate anaerobic digestion of municipal wastes and waste activated sludge (biosolids). Bench-scale, semi-continuous, mesophilic reactors were operated with a 21-day mass-retention time and dosed with NH4Cl, such that the corresponding chemical O2 demand (COD)/N ratios in their feeds were 90, 80, 65 and 50 (reactors R1 or control, R2, R3 and R4 respectively). Reactor performance was evaluated in terms of the efficiency of volatile solid removal (efficiency for short), biogas productivity, methane content in the biogas, pH and volatile organic acid contents, among other monitoring and analytical parameters. The feedstock was a mixture of urban wastes with biosolids. It was found that the process performance deteriorated at increasing dosages of ammonia N, the process practically ceasing at COD/N = 50 (R4). Inhibition was characterized by efficiency and biogas productivity decreases and a more sudden drop of methane content in biogas and pH. A significant rise of propionic, butyric and valeric acid was found in reactors receiving the highest doses of ammonia N (R3 and R4). This suggested that inhibition of the syntrophic bacteria present in the anaerobic consortia also occurred. Luong and Pearson inhibition models were fitted to the data. Both models represented very well the acute effects of N supplementation on solid-substrate anaerobic digestion. However, the Luong model could also represent the process ceasing at a critical ammonia N concentration of 2800 mg/kg mixed solids.
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    Catechol dioxygenase expression in a Pseudomonas fluorescens strain exposed to different aromatic compounds (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 306-308 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Batch cultures of Pseudomonas fluorescens (strain P2a) maintained under carbon-limiting conditions in the presence of chrysene and other aromatics, survived starvation with no detectable changes in cell number for at least 4 months. P2a also demonstrated high dioxygenase levels after growth on benzoate and catechol. To characterize this strain further, early stationary-phase cells were resuspended in fresh mineral medium containing different aromatics, to evaluate enzyme expression in the presence of high-molecular-mass (isocyclic and heterocyclic) compounds. Results demonstrated effects on catechol 1,2-dioxygenase modulation by the model compounds used, confirming a low substrate specificity for this enzyme. The increases of specific activity observed in the presence of heterocyclic compounds were higher than those observed with isocyclic compounds.
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    Synthetic spider dragline silk proteins and their production in Escherichia coli (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 23-32 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Synthetic genes were designed to encode analogs of the two proteins of Nephila clavipes dragline silk, spidroins 1 and 2. The genes were constructed of tandem repeats of relatively long (more than 300 bp) DNA sequences assembled from synthetic oligonucleotides, and encoded proteins of high molecular mass (65–163 kDa). Both analogs were produced efficiently in Escherichia coli. The yield and homogeneity of the products of longer genes were limited by premature termination of synthesis, probably as a result of processivity errors in protein synthesis. Average termination rates were determined to be 1 in 1100 codons to 1 in 300 codons, depending on the length and synonymous codon choices of the gene. Both analog proteins could be induced to form stable aqueous solutions without denaturants. Circular dichroism spectra of the purified proteins in dilute solution resembled spectra of redissolved natural dragline silk in reflecting a largely disordered structure in water and more ordered structures in mixed solvents with methanol and trifluoroethanol.
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    Improvement of culture conditions to overproduce β-galactosidase from Escherichia coli in Bacillus subtilis (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 40-45 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of some culture variables in the production of β-galactosidase from Escherichia coli in Bacillus subtilis was evaluated. The lacZ gene was expressed in B. subtilis using the regulatory region of the subtilisin gene aprE. The host contained also the hpr2 and degU32 mutations, which are known to overexpress the aprE gene. We found that, when this overproducing B. subtilis strain was grown in mineral medium supplemented with glucose (MMG), β-galactosidase production was partially growth-associated, as 40%–60% of the maximum enzyme activity was produced before the onset of the stationary phase. In contrast, when a complex medium was used, β-galactosidase was produced only at low levels during vegetative growth, whereas it accumulated to high levels during early stationary phase. Compared with the results obtained in complex media, a 20% increase in specific β-galactosidase activity in MMG supplemented with 11.6 g/l glucose was obtained. On the 1-l fermenter scale, a threefold increase in volumetric β-galactosidase activity was obtained when the glucose concentration was varied from 11 g/l to 26 g/l. In addition, glucose feeding during the stationary phase resulted in a twofold increase in volumetric enzyme activity as cellular lysis was prevented. Finally, we showed that oxygen uptake and carbon dioxide evolution rates can be used for on-line determination of the onset of stationary phase, glucose depletion and biomass concentration.
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    Use of immobilized bacteria to treat industrial wastewater containing a chlorinated pyridinol (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 73-77 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Pseudomonas sp. strain M285 immobilized on diatomaceous earth beads was used to remove 3,5,6-trichloro-2-pyridinol (TCP) from industrial wastewater. Batch studies showed that immobilized Pseudomonas sp. strain M285 mineralized [2,6-14C]TCP rapidly; about 75% of the initial radioactivity was recovered as 14CO2. Transformation of TCP was inhibited by high concentrations of salt, and addition of osmoprotectants (proline and betaine at 1 mM) did not reduce the adverse effect of salt. TCP-containing wastewater (60–140 mg/l) was passed through columns containing immobilized Pseudomonas sp. strain M285 at increasing flow rates and increasing TCP concentrations; TCP removal of 80%–100% was achieved. Addition of nutrients, such as glucose and yeast extract, retarded TCP degradation. Growing cell cultures were found to be better inocula for immobilization than resting cells.
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    Corrosion inhibition by aerobic biofilms on SAE 1018 steel (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 62-68 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Carbon steel (SAE 1018) samples were exposed to complex liquid media containing either the aerobic bacterium Pseudomonas fragi or the facultative anaerobe Escherichia coli DH5α. Compared to sterile controls, mass loss was consistently 2- to 10-fold lower in the presence of these bacteria which produce a protective biofilm. Increasing the temperature from 23 °C to 30 °C resulted in a 2- to 5-fold decrease in corrosion inhibition with P. fragi whereas the same shift in temperature resulted in a 2-fold increase in corrosion inhibition with E. coli DH5α. Corrosion observed with non-biofilm-forming Streptomyces lividans TK24 was similar to that observed in sterile media. A dead biofilm, generated in situ by adding kanamycin to an established biofilm, did not protect the metal (corrosion rates were comparable to those in the sterile control), and mass loss in cell-free, spent Luria-Bertani (LB) medium was similar to that in sterile medium. Confocal laser scanning microscopy analysis confirmed the presence of a biofilm consisting of live and dead cells embedded in a sparse glycocalyx matrix. Mass-loss measurements were consistent with microscopic observations of the metal surface after 2 weeks of exposure, indicating that uniform corrosion occurred. The biofilm was also able to withstand mild agitation (60 rpm), provided that sufficient time was given for its development.
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    Development of a phosphate-removal system using a marine photosynthetic bacterium Chromatium sp. (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 78-82 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The marine photosynthetic bacterium Chromatium sp. successfully removed orthophosphate when grown phototrophically. The phosphate-uptake rate was almost constant at more than 5.0 mg- PO4 3−/l in synthetic medium. Addition of seawater causes flocculation of this strain. The successful use of seawater as an inexpensive source of magnesium could prove to be effective in the removal of photosynthetic bacterial cells from a medium. A semicontinuous culture system was used for the removal of low concentrations of phosphate and the phosphate-uptake activity of Chromatium sp. was maintained under 0.1 day−1 dilution rate. This strain was also able to remove high concentrations of phosphate from domestic sewage.
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    Transformation of tetrachloroethene in an upflow anaerobic sludgeblanket reactor (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 91-94 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract   Reductive dechlorination of tetrachloroethene was studied in a mesophilic upflow anaerobic sludge blanket reactor. Operating the reactor in batch mode the dynamic transformation of tetrachloroethene, trichloroethene and dichloroethene (DCE) was monitored. Tetrachloroethene was reductively dechlorinated to trichloroethene, which again was dechlorinated at the same rate as DCE was produced. DCE showed a lag period of 40 h before transformation was observed. During normal reactor operation trans-1,2-DCE was the major DCE isomer, followed by cis-1,2-DCE. Small amounts of 1,1-DCE but no vinyl chloride were detected. When the influent tetrachloroethene concentration was increased from 4.6 μM to 27 μM, the transformation rate increased, indicating that the system was not saturated with tetrachloroethene. The main organic component in the effluent was acetate, indicating that the aceticlastic methane-producing bacteria were inhibited by the chlorinated ethenes.
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    Breeding of starch-utilizing and itaconic-acid-producing koji molds by interspecific protoplast fusion between Aspergillus terreus and Aspergillus usamii (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 127-131 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Interspecific protoplast fusion between␣Aspergillus terreus, an itaconic acid producer, and A.␣usamii, a glucoamylase producer, was done to breed new koji molds producing itaconic acid from starch. Protoplast fusion between auxotrophic mutant strains by poly(ethylene glycol) treatment produced prototrophic fusants with a fusion frequency of 10−5−10−4. The stabilities of some fusants obtained were confirmed by successive subcultures. Conidial analyses of DNA contents and the number of nuclei indicated that the fusants obtained were haploids like the parental strains. One of the stable fusants, F-112, morphologically resembled A. terreus, and produced maximally 35.9 mg/ml itaconic acid from soluble starch (120 mg/ml) at day 6 of cultivation. This productivity from soluble starch was five times as high as that of A. terreus and 70 % of that of A. terreus from glucose (120 mg/ml).
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    Growth conditions of Aspergillus sp. ATHUM-3482 for polygalacturonase production (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 425-429 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A wild type of Aspergillus sp. ATHUM-3482 produced extracellular polygalacturonase when grown in liquid medium containing citrus pectin as sole carbon source. A number of factors affecting enzyme activity were investigated. Polygalacturonase activities as high as␣4.3 U␣ml−1(reducing-group-releasing activity) and 17␣U␣ml−1 (viscosity-diminishing activity) were obtained under optimum growth conditions. With sugar-beet as sole carbon source the respective activities were 6.5 U␣ml−1 and 40 U ml−1, the highest achieved in this work. Under these conditions no pectin lyase or pectinesterase activity was detected. The above yields of polygalacturonase activity compare favourably with those reported for fungi grown under similar growth conditions.
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    Propionic acid fermentation from glycerol: comparison with conventional substrates (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 441-446 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Instead of the conventional carbon sources used for propionic acid biosynthesis, the utilization of glycerol is considered here, since the metabolic pathway involved in the conversion of glycerol to propionic acid is redox-neutral and energetic. Three strains, Propionibacterium acidipropionici, Propionibacterium acnes and Clostridium propionicum were tested for their ability to convert glycerol to propionic acid during batch fermentation with initially 20 g/l glycerol. P. acidipropionici showed higher efficiency in terms of fermentation time and conversion yield than did the other strains. The fermentation profile of this bacterium consisted in propionic acid as the major product (0.844 mol/mol), and in minimal by-products: succinic (0.055 mol/mol), acetic (0.023 mol/mol) and formic (0.020 mol/mol) acids and n-propanol (0.036 mol/mol). The overall propionic acid productivity was 0.18 g l−1h−1. A comparative study with glucose and lactic acid as carbon sources showed both less diversity in end-product composition and a 17% and 13% lower propionic acid conversion yield respectively than with glycerol. Increasing the initial glycerol concentration resulted in an enhanced productivity up to 0.36 g l−1h−1 and in a maximal propionic acid concentration of 42 g/l, while a slight decrease of the conversion yield was noticed. Such a propionic acid production rate was similar or higher than the values obtained with lactic acid (0.35 g l−1h−1) or glucose (0.28 g l−1h−1). These results demonstrated that glycerol is a carbon source of interest for propionic acid production.
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    Isolation and characterization of Rhodococcus rhodochrous for the degradation of the wastewater component 2-hydroxybenzothiazole (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 458-461 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract 2-Hydroxybenzothiazole (OBT) is present in wastewaters from the industrial production of the rubber vulcanization accelerator 2-mercaptobenzothiazole (MBT). We have achieved the first isolation of axenic bacterial cultures capable of the degradation of OBT and growth on this substrate as the sole source of carbon, nitrogen and energy. All isolates had similar characteristics corresponding to one particular isolate, which was studied in more detail and identified as Rhodococcus rhodochrous. The strains were also capable of degrading benzothiazole (BT) but not MBT or benzothiazole-2-sulphonate (BTSO3). OBT was degraded at a concentration of up to 600 mg · l−1. BT was toxic above 300 mg · l−1. MBT inhibited OBT degradation. Growth on OBT was not significantly different at pH values of between 6.3 and 7.9 or salt concentrations between 1 % and 3 %. In shake flasks the cells clumped together, which resulted in a lower rate of oxygen transfer and slower degradation as compared to cells grown on OBT in a stirred reactor.
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    Pyrazine production by Bacillus subtilis in solid-state fermentation on soybeans (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 489-495 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract 2,5-Dimethylpyrazine (2,5-DMP) and tetramethylpyrazine (TTMP) were produced using Bacillus subtilis IFO 3013 grown on soybeans. Solid-state cultivations were carried out either in 100-ml bottles or in a fixed-bed column reactor, both systems being at 27 °C. Optimization studies showed that the best way to produce the two above aroma compounds involved two separate processes. 2,5-DMP was obtained using soybeans enriched with 75 g threonine/kg initial dry weight (i.d.w.), giving 0.85 g metabolite/kg i.d.w. after 6 days. TTMP production involved addition of 90 g/kg i.d.w. acetoin to soybeans, and 2.5 g/kg i.d.w. was recovered after 14 days. These results demonstrated the suitability of solid-state cultivation for production of high-added-value compounds.
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    Enantioselective reduction of 3,4-methylene-dioxyphenylacetone using Candida famata and Zygosaccharomyces rouxii (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 162-166 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In an effort to prepare 3,4-methylene-dioxyphenyl-(S)-isopropanol from 3,4-methylene-dioxyphenylacetone, an initial screen of microbes indicated that Candida famata could catalyze this reaction efficiently at low substrate concentration. A dilute, large-scale process was developed to provide experimental material for the chemical synthesis to be explored. However, the productivity number of this process [0.134 g product (g␣wet␣weight cells)−1 day−1 was too low to be practical. C.␣famata was also extremely sensitive to concentrations of both the ketone and the alcohol greater than 2 g/l. A more extensive screen of yeast and fungi revealed that Zygosaccharomyces rouxii was more tolerant to higher substrate concentrations and had a higher productivity number [0.8 g (g wet weight cells)−1 day−1]. These characteristics suggested that Z. rouxii could be used in a large-scale process at high substrate concentrations.
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    d-Methionine preparation from racemic methionines by Proteus vulgaris IAM 12003 with asymmetric degrading activity (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 173-179 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The microbial degradation of l-methionine was investigated in order to develop a practical process for d-methionine production from racemic methionines. Among the 1000 culture strains tested, microorganisms belonging to the Achromobacter, Bacillus, Micrococcus, Morganella, Proteus, Providencia, Pseudomonas and Sarcina genera exhibited a high l-methionine-degrading activity. Proteus vulgaris IAM 12003 was determined to be the best strain and was used as a biocatalyst for eliminating the l-isomer. The degradation of l-isomer in this P. vulgaris IAM 12003 cell was assured by the action of l-amino acid oxidase. The maximum rate of l-isomer degradation was obtained at 30 °C and pH 8.0. Under these optimal conditions, the l-isomer in a 100 g/l mixture of racemic methionines was almost degraded within 20 h, with 46.5 g d-methionine/l remaining in the reaction mixture. Crystalline d-methionine, with a chemical purity greater than 99% and optical purity of 99.9% enantiomeric excess, was obtained at a yield of 30% from the reaction mixture by simple purification.
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    Influence of the starting microbial nucleus type on the anaerobic granulation dynamics (1997)
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    Applied microbiology and biotechnology 47 (1997), S. 189-194 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The influence of four different granulation precursors, syntroph-enriched methanogenic consortia, Methanosaeta-enriched, Methanosarcina-enriched nuclei and acidogenic flocs, on the time course of complex granule development and the lag time for start-up was investigated in four upflow anaerobic sludge-bed and filter reactors. Although the operational conditions allowed the maintenance of the same specific growth rate of biomass in the four reactors, granulation proceeded rapidly with syntroph/methanogenic consortia, Methanosaeta and Methanosarcina nuclei. However, granulation was significantly retarded when acidogenic flocs were used as precursors. The granule mean Sauter diameter increased rapidly in the reactor inoculated with syntroph/methanogenic consortia, Methanosaeta and Methanosarcina nuclei and reached, at the end of the experiment, 3.1, 2.7 and 2.4 mm compared to 1.1 mm in that inoculated with acidogenic flocs. This corresponded to a rate of granule size increase of 31, 21, 18 μm/day in syntroph/methanogenic consortia, Methanosaeta and Methanosarcina nuclei, respectively, compared to 7 μm/day in acidogenic flocs. Biomass specific activities (i.e. acidogenic, syntrophic and methanogenic activities) increased stepwise in all reactors with time, especially in those inoculated with syntroph/methanogenic consortia and Methanosaeta nuclei. From these results it appears that syntrophs and Methanosaeta spp. play an important role in the anaerobic granulation process.
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    Enrichment strategies for nitrile-hydrolysing bacteria (1997)
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    Applied microbiology and biotechnology 47 (1997), S. 668-674 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A series of enrichments with different nitriles as sole source of nitrogen was performed in order to obtain a relationship between the selective nitrogen source and (i) the enzyme systems that are synthesized by the isolates and (ii) the enzyme specificities for the utilization of the nitriles. Bacteria were enriched with 2-phenylpropionitrile, 2-(2-methoxyphenyl)propionitrile, 2-phenylbutyronitrile, ibuprofen nitrile, naproxen nitrile, ketoprofen nitrile, ketoprofen amide, benzonitrile, or naphthalenecarbonitrile as sole nitrogen source and succinate as sole source of carbon and energy. 2-Phenylpropionitrile as nitrogen source resulted predominantly in the enrichment of gram-negative bacteria, which harboured nitrilase and in some cases also amidase activity. In contrast, with the other nitriles used, a substantial majority of gram-positive strains, mainly of the genus Rhodococcus, were isolated. These strains contained predominantly a nitrile hydratase/amidase system. The nitrilases and nitrile hydratases showed R or S selectivity with generally poor optical yields. In contrast, the amidases were almost exclusively S-selective, often forming the optically pure acids with an enantiomeric excess above 99%. The conversion of different nitriles by the isolates was compared. The nitrile-hydrolysing systems of the new isolates usually showed high activity against those nitriles that were used for the enrichment of the bacteria.
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    Effects of yeast extract and glucose on xanthan production and cell growth in batch culture of Xanthomonas campestris (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 689-694 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Although available kinetic data provide a useful insight into the effects of medium composition on xanthan production by Xanthomonas campestris, they cannot account for the synergetic effects of carbon (glucose) and nitrogen (yeast extract) substrates on cell growth and xanthan production. In this work, we studied the effects of the glucose/yeast-extract ratio (G/YE) in the medium on cell growth and xanthan production in various operating modes, including batch, two-stage batch, and fed-batch fermentations. In general, both the xanthan yield and specific production rate increased with increasing G/YE in the medium, but the cell yield and specific growth rate decreased as G/YE increased. A two-stage batch fermentation with a G/YE shift from an initial low level (2.5% glucose/0.3% yeast extract) to a high level (5.0% glucose/0.3% yeast extract) at the end of the exponential growth phase was found to be preferable for xanthan production. This two-stage fermentation design both provided fast cell growth and gave a high xanthan yield and xanthan production rate. In contrast, fed-batch fermentation with intermittent additions of glucose to the fermentor during the stationary phase was not favorable for xanthan production because of the relatively low G/YE resulting in low xanthan production rate and yield. It is also important to use a moderately high yeast extract concentration in the medium in order to reach a high cell density before the culture enters the stationary phase. A high cell density is also important to the overall xanthan production rate.
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    13C NMR cross polarization and magic angle spinning (CPMAS) and gas chromatography/mass spectrometry analysis of the products from a soda pulp mill effluent decolourised by two Streptomyces strains (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 272-278 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two Streptomyces strains, UAH 30 and UAH 51, have been shown to decolourise a paper-mill effluent obtained after semichemical alkaline pulping of wheat straw. Fractionation of the effluent decolourised by strains UAH 30 and UAH 51 showed that 60% and 80% respectively of the alkali-lignin fraction have been removed from the effluent after 7 days of growth. 13C NMR cross polarization and magic angle spinning (CPMAS) spectra of the alkali-lignin remaining in the effluent after decolourisation revealed a decrease in the relative amount of aromatic lignin units compared to that obtained from the untreated effluent along with a reduction in the ratio of syringyl:guaiacyl units. Gas chromatography/mass spectrometry analysis of the low-molecular-mass compounds extracted from the decolourised effluent revealed the presence of new aromatic lignin-related compounds that were not present in the untreated control effluent. This was linked to a general depolymerization of larger lignin molecules occurring during decolourisation by the two Streptomyces strains. Identification of low-molecular-mass aromatic compounds extracted from the decolourised effluent revealed only the presence of p-hydroxyphenyl units in effluents decolourised by the strain UAH 30 while p-hydroxyphenyl, guaiacyl and syringyl units were detected in effluents decolourised by Streptomyces strain UAH 51. The study indicates that, while decolourisation is a common feature of the two Streptomyces strains, the mechanisms involved in the degradation of the lignin fractions may be different and strain-specific.
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    Batch and fed-batch bioreactor cultivations of a Thermus species with thermophilic BTEX-degrading activity (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 726-733 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The thermophilic bacterium, Thermus species ATCC 27978, which is capable of aerobically degrading benzene, toluene, ethylbenzene, and the xylenes (BTEX), was cultured in 5-1 fermentors on a Castenholz salts-tryptone medium. This bacterium can be cultivated more conveniently at 45 °C, a temperature substantially lower than its optimal growth temperature (approx. 60 °C). Yet, the washed harvested cells from such cultures display the same initial BTEX-degrading activity as those when Thermus sp. is grown at its higher optimal temperature. Two bioreactor cultivation modes, batch and fed batch, were investigated. More biomass and more BTEX-degrading activity (assayed at 60 °C) were generated in fed-batch cultures than in the growth-limited batch cultures. The former yielded a biomass concentration of 2.5 g dry cell weight (DCW) l−1 and whole-cell degrading specific activities of 7.6 ± 1.3, 10.1 ± 1.9, 9.8 ± 2.1, 2.3 ± 0.5, and 4.6 ± 0.9 nmol degraded (mg DCW)−1 min−1 for benzene, toluene, ethylbenzene, m-xylene, and the o- plus p-xylenes (unresolved mixture), respectively. Although the formation of cellular BTEX-degrading activity is growth-associated, a slow to moderate specific growth rate of 0.02–0.07 h−1 favors the production of BTEX-degrading activity, while a high growth rate, of the order of 0.16 h−1, is detrimental to its production. The washed harvested Thermus sp. cells were capable of degrading BTEX over a broad range of thermophilic incubation temperatures, 45–77 °C.
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    Effect of soybean oil and glucose on sophorose lipid fermentation by Torulopsis bombicola in continuous culture (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 23-26 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The effect of soybean oil and glucose on the growth of Torulopsis bombicola and sophorose lipid production in continuous culture was investigated. As the dilution rate in 100 g/l glucose and 100 g/l soybean oil medium was increased, the dry cell weight and sophorose lipid concentration decreased. Sophorose lipid productivity, however, was maximum at a dilution rate of 0.03 h−1. The cell yield from glucose and the sophorose lipid production from soybean oil were approximately constant regardless of the dilution rate. The specific consumption rate of soybean oil was closely related to the specific production rate of sophorose lipid. These results suggest that soybean oil was used only for sophorose lipid production whereas glucose was used only for cell mass and maintenance. When the soybean oil concentration was varied at fixed dilution rate in 100 g/l glucose medium, a high concentration of soybean oil was found to inhibit sophorose lipid production.
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    Axenic aerobic biofilms inhibit corrosion of SAE 1018 steel through oxygen depletion (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 11-17 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Corrosion inhibition of SAE 1018 steel by pure-culture biofilms of Pseudomonas fragi and Escheri-chia coli DH5α has been evaluated in complex Luria-Bertani medium, seawater-mimicking medium, and modified Baar's medium at 30 °C. In batch cultures, both bacteria inhibited corrosion three to six fold compared to sterile controls, and the corrosion was comparable to that observed in anaerobic sterile media. To corroborate this result, a continuous reactor and electrochemical impedance spectroscopy were used to show that both P. fragi K and E. coli DH5α decreased the corrosion rate by 4- to 40-fold as compared to sterile controls; this matched the decrease in corrosion found with sterile medium in the absence of oxygen and with E. coli DH5α grown anaerobically. In addition, the requirement for live respiring cells was demonstrated by the increase in the corrosion rate that was observed upon killing the P. fragi K biofilm in continuous cultures, and it was shown that fermentation products do not cause an increase in corrosion. Hence, pure-culture biofilms inhibit corrosion of SAE 1018 steel by depleting oxygen at the metal surface.
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    Reactivation of thermally inactivated enzymes by free and immobilized chaperonin GroEL/ES (1997)
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    Applied microbiology and biotechnology 48 (1997), S. 41-46 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Thermally inactivated bovine deoxyribonuclease I (DNase I) and yeast enolase were reactivated by GroEL/ES from Escherichia coli. In both cases, GroEL/ES was found to have the ability to reactivate inactivated enzymes in an ATP-dependent manner. GroEL/ES can interact with the enzymes that were denatured at high temperature and convert them to the active conformations. To test the applicability of GroEL/ES to the reactivation processes of thermally inactivated enzymes, GroEL/ES was immobilized using formyl-Cellulofine (GroEL/ES-Cellulofine) and its performance was studied. GroEL/ES-Cellulofine retained a sufficiently high ability to reactivate enzymes. Moreover, GroEL/ES-Cellulofine could be used repeatedly, indicating high durability. These results indicate that immobilized chaperonin is effective for reactivation of enzymes that are thermally inactivated in various bioprocesses.
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    Efficient synthesis of the blood-coagulation inhibitor hirudin in the filamentous fungus Acremonium chrysogenum (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 58-65 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The isopenicillin-N-synthetase-encoding pcbC gene from the filamentous fungus Acremonium chrysogenum is differentially expressed in strains showing either a high or low cephalosporin C production. For a case study to demonstrate heterologous protein synthesis in A. chrysogenum, we have chosen a synthetic 195-bp gene encoding the thrombin inhibitor hirudin from the leech Hirudo medicinalis. The hirudin gene was fused with the 5′ and 3′ regions of the pcbC gene, resulting in four different expression vectors, which we named pHIR1 to pHIR4. In order to achieve secretion of the heterologous polypeptide, two out of four vectors carry, in addition, secretion signal sequences of an alkaline protease gene originating either from Fusarium sp. or from A. chrysogenum. After DNA-mediated transformation of the two A. chrysogenum strains, transformants were further analysed on the transcriptional and translational level. Irrespective of the vector used for transformation, all transformants show a hirudin-genespecific transcript in Northern hybridizations. In further analysis, hirudin synthesis was determined with a thrombin-inhibition assay, but was detectable only in those strains carrying expression plasmids with the secretion signals. In this case, hirudin was secreted into the culture medium. Transformants from strains with a high cephalosporin C production showed a three- to eightfold higher expression of the hirudin gene compared to low cephalosporin-C-producing strains. The amount of recombinant hirudin was quantified further by ELISA and Western blotting, using a monoclonal antibody directed against recombinant hirudin. Finally, the time course of hirudin gene expression was investigated in a selected transformant that has hirudin activities of 8.0 ATU/ml culture medium. Northern hybridization experiments revealed the highest hirudin transcript level after 2–5 days of cultivation, showing the strongest signal after 3 days. After 4–5 days, we detected the highest hirudin activity, as was confirmed by Western blotting. The level of heterologous hirudin synthesis in A. chrysogenum is discussed in relation to other eukaryotic expression systems.
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    Biotransformation of linoleic acid with the Candida tropicalis M25 mutant (1997)
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    Applied microbiology and biotechnology 48 (1997), S. 83-87 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Linoleic acid was transformed by mutant Candida tropicalis M25 and transformations were studied in batch and fed-batch cultures. Cofermentations with palmitic acid as inducer of the fatty acid degradation pathway were performed. Besides the (Z),(Z)-octadeca-6,9-dienedioic acid, (Z),(Z)-3-hydroxyoctadeca-9,12-dienedioic acid and (Z),(Z)-3-hydroxytetradeca-5,8-dienedioic acid were obtained as the main fermentation products. The maximum concentrations of (Z),(Z)-octadeca-6,9-dienedioic acid and (Z),(Z)-3-hydroxyoctadeca-9,12-dienedioic acid reached values of 6.4 g/l and 6.9 g/l respectively. The structures of the products were characterized by chemical and spectroscopic methods. The configuration of the double bonds was not changed during bioconversion. As only one regioisomer of the hydroxylated fatty acid was detected, the hydroxylation is site-specific.
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    Creating auxotrophic mutants in Methylophilus methylotrophus AS1 by combining electroporation and chemical mutagenesis (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 105-108 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Stable auxotrophic mutants of the methylotroph Methylophilus methylotrophus AS1 were obtained by a novel mutagenesis technique in which electroporation is used to transport the chemical mutagen N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) across the cell membrane. By combining chemical mutagenesis with electroporation and screening single colonies for auxotrophy in 36 different amino acids and growth factors, 3 auxotrophs per 156 colonies screened were obtained, whereas no auxotrophs were found with chemical mutagenesis alone. MNNG mutagen toxicity was also increased in the methylotroph with this novel mutagenesis technique (death rate 96% compared to 79%). This technique did not increase the mutation rate for strain Escherichia coli BK6 which responds well to simple exposure to the mutagen.
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    Initiation of [36Cl]hexachlorobenzene dechlorination in three different soils under artificially induced anaerobic conditions (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 115-120 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The potential for reductive dechlorination of hexachlorobenzene was investigated in samples of three different, naturally oxic soils held under conditions of high oxygen deficiency. The soils were water-saturated and the influence on dechlorination of adding different electron donors, a surfactant and an anaerobic microbial consortium was tested. The influence of supplied electron donors seems to depend on the organic matter content of the soils. Dechlorination in the organic-matter-rich soil from Maulach was not affected by amendment with organic electron donors. A release of about 40% chloride within 140 days was observed for this soil in all biotic-treated assays. By contrast, the organic-matter-poor soil of Eppingen showed no dechlorination in unamended assays. However, when it was supplemented with organic electron donors dechlorination of 2%–37% occurred within 140 days, depending on the type of electron donor. Complex substrate (wheat strawdust), from which carbon is slowly liberated, gave the best results. These two soils had an indigenous dechlorinating anaerobic microflora, whereas the third soil (Rastatt) required inoculation with an anaerobic consortium for dechlorination. The addition of electron donors alone did not cause dechlorination in this sandy soil. The addition of a surfactant (Tween 80) to increase the bioavailability of hexachlorobenzene did not enhance dechlorination. This process was not inhibited by inherent alternative electron acceptors in soil (NO3−, SO4 2−, Fe3+). The dechlorination did not require methanogenic conditions.
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    Production of zeaxanthin in Escherichia coli transformed with different carotenogenic plasmids (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 162-167 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Carotenoids are of great commercial interest and attempts are made to produce different carotenoids in transgenic bacteria and yeasts. Development of appropriate systems and optimization of carotenoid yield involves transformation with several new genes on suitable plasmids. Therefore, the non-carotenogenic bacterium Escherichia coli JM101 was transformed in our study with several genes that mediated the biosynthetic production of the carotenoid zeaxanthin in this host. Selection of plasmids for the introduction of five essential genes for zeaxanthin formation showed that a pACYC-derived plasmid was the best. Multiplasmid transformation generally decreased production of zeaxanthin. By cotransformation with different plasmids, limitations in the biosynthetic pathway were found at the level of geranylgeranyl-pyrophosphate synthase and β-carotene hydroxylase. In our study a maximum zeaxanthin content of 289 μg/g dry weight was obtained. This involved the construction of a plasmid that mediated high-level expression of β-carotene hydroxylase. The level of expression was demonstrated on protein gels and solubilization by the mild detergent Brij 78 revealed that a significant portion of the expressed enzyme is located in the E. coli membranes where it can exert its catalytic function. Based on the results obtained, new strategies for vector construction and strain selection were proposed which could increase the present concentrations drastically. Optimal growth conditions of the transfomed E. coli strains for carotenoid formation were found at a temperature of 28 °C and a cultivation period of 2 days.
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    Plant cell suspension culture in a bench-scale fermenter with a newly designed membrane stirrer for bubble-free aeration (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 149-154 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract In this paper, tests of an optimized membrane-stirrer geometry for bubble-free aeration of a plant cell suspension culture are described. Cell attachment and clogging of a previously described system [Piehl et al. (1988) Appl Microbiol Biotechnol 29:456–461] led to the development of a new stirrer. The volumetric oxygen transfer capacity has been measured in aqueous medium. The mass transfer coefficient, k l a, was 3.75 h−1 at 25 °C and at a stirrer speed of 34 rpm. The overall oxygen transfer capacity was investigated with a suspension culture of Aesculus hippocastanum. It was shown that the oxygen mass transfer was sufficient even at the maximum biomass of 10–12 g dry weight/l, which was obtained by using this system. Furthermore, special attention was given to medium components like C and N sources, to avoid growth limitation due to a shortage of nutrients.
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    On-line enzyme activity determination using the stopped-flow technique: application to laccase activity in pulp mill waste-water treatment (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 168-173 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An automated system for on-line measurement of enzyme activity is proposed. The system uses a flow injection manifold in the stopped-flow mode to measure initial reaction rates. The time during which the flow is halted is selected in such a way as to optimise the enzyme/substrate ratio for the correct determination of activity values. The proposed system was used to determine the activity of laccase produced by the fungus Trametes versicolor immobilised on nylon in a fixed-bed reactor used for treating pulp mill waste water.
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    URL: http://dx.doi.org/10.1007/s002530051033
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    The effect of oxidative stress on the production of the recombinant protein, interferon γ, produced by Chinese hamster ovary cells in stirred-batch culture (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 198-203 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The CHO320 cell line, engineered to produce human interferon γ was investigated with regard to its susceptibility to oxidative stress. Batch cultures of the cells grown in a bench-top bioreactor exhibited no marked response to changes in oxygen concentration between 6% and 14% whereas cell growth and recombinant protein production were inhibited by increasing the oxygen to 20%. High concentrations of hydrogen peroxide (in excess of 200 μM) were required to inhibit growth of the CHO320 cells whereas concentrations of 50 μm and 100 μM had no effect on recombinant protein production. Buthionine sulphoximine (50 μM and 100 μM) completely depleted the cells of glutathione within 24 h; however, no quantitative effect on recombinant protein production was seen. It is concluded that the CHO320 cells are, possibly as a consequence of the long selection process they have undergone, very resistant to oxidative stress.
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    Stabilization of Escherichia coli penicillin G acylase against thermal inactivation by cross-linking with dextran dialdehyde polymers (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 191-197 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The thermostabilization of penicillin G acylase (PGA) obtained from a mutant of Escherichia coli ATCC 11105 by cross-linking with dextran dialdehyde molecules, at a molecular mass of 11 500, 37 700 and 71 000 Da, was studied. The thermal inactivation mechanisms of the native and modified PGA were both considered to obey first-order inactivation kinetics during prolonged heat treatment, forming fully active but temperature-sensitive transient states. The highest enhancement to the thermostability of PGA was obtained using dextran-71000-dialdehyde modification, as a␣nearly ninefold increase at temperatures above 50 °C. The modification of PGA by dextran-11500-dialdehyde resulted in a considerable reduction of the V m and K m parameters of the enzyme. However, other dextran dialdehyde derivatives used for modification did not cause a meaningful change in either V m and K m. Modification by dextran dialdehyde derivatives did not result in significant change to either the optimal temperature or the activation energy of PGA. All modified PGA preparations showed lower inactivation rate constants but higher half-lives for inactivation than those of the native PGA at all temperatures studied. As indicated by the half-life times and k i values, dextran 71000-dialdehyde was found to be more effective at cross-linking in the thermo-stabilization of PGA than any other agent studied in this work.
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    Cloning, expression in Streptomyces lividans and biochemical characterization of a thermostable endo-β-1,4-xylanase of Thermomonospora alba UL JB1 with cellulose-binding ability (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 208-217 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Several thermophilic actinomycetes were isolated from urban solid waste. One of them, Thermomonospora alba ULJB1, showed a broad degradative activity on xylan, cellulose, starch and other polymers. Xylanase and cellulase activities were quantified and compared with those of Thermomonospora fusca. Genes encoding two different endo-β-1,4-xylanases were cloned from T.␣alba ULJB1. One of them, xylA, was sequenced, subcloned and overexpressed in Streptomyces lividans. It encodes a protein of 482 amino acids with a deduced molecular mass of 48 456 Da. The protein contains a 38-amino-acid leader peptide with six Arg+ residues in its amino-terminal end, a catalytic domain and a cellulose-binding domain connected by a linker region rich in proline and glycine. The XylA protein was purified to near homogeneity from S. lividans/xylA cultures. Two forms of the extracellular xylanase, of 48 kDa and 38 kDa, were produced that differed in their cellulose-binding ability. The 48-kDa protein showed a strong binding to cellulose whereas the 38-kDa form did not bind to this polymer, apparently because of the removal during processing of the cellulose-binding domain. Both forms were able to degrade xylans form different origins but not lichenam or carboxymethylcellulose. The major degradation product was xylobiose with traces of xylose. The xylanase activity was thermostable, showing a good activity up to 95 °C, and had broad pH stability in the range from pH 4.0 to pH 10.0.
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    Production of exopolysaccharide by Pseudomonas sp. ATCC 31461 (Pseudomonas elodea ) using whey as fermentation substrate (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 52-57 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An improved strain of Pseudomonas sp. ATCC 31461 (Pseudomonas elodea), capable of producing broth viscosities of 11 000 and 4700 mPa s (cP) when grown in enriched whey permeate and enriched sweet whey broths respectively, was isolated. The isolation was by serial transfers of the parent on lactose-rich and sweet whey broths. Maximum viscosities and biopolymer production were observed in 25% (v/v) whey concentration. In whey concentrations of 50% (v/v) or greater, residual glucose was detected in the broth and biopolymer production was low. This strain is capable of totally utilising the lactose in up to 50% (v/v) whey in 64 h. Enzyme activities suggest that the transport of lactose in P. elodea is by the permease system as opposed to the phosphotransferase system. The location of β-galactosidase is mainly intracellular. The improved strain is able to utilise lactose better than the parent and produce 1.6 times more intracellular β-galactosidase activity compared to the parent.
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    Biodegradation of methyl t-butyl ether by pure bacterial cultures (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 69-72 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Three pure bacterial cultures degrading methyl t-butyl ether (MTBE) were isolated from activated sludge and fruit of the Gingko tree. They have been classified as belonging to the genuses Methylobacterium, Rhodococcus, and Arthrobacter. These cultures degraded 60 ppm MTBE in 1–2 weeks of incubation at 23–25 °C. The growth of the isolates on MTBE as sole carbon source is very slow compared with growth on nutrient-rich medium. Uniformly-labeled [14C]MTBE was used to determine 14CO2 evolution. Within 7 days of incubation, about 8% of the initial radioactivity was evolved as 14CO2. These strains also grow on t-butanol, butyl formate, isopropanol, acetone and pyruvate as carbon sources. The presence of these compounds in combination with MTBE decreased the degradation of MTBE. The cultures pregrown on pyruvate resulted in a reduction in 14CO2 evolution from [14C]MTBE. The availability of pure cultures will allow the determination of the pathway intermediates and the rate-limiting steps in the degradation of MTBE.
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    Enhanced mineralization of pentachlorophenol by κ-carrageenan-encapsulated Pseudomonas sp. UG30 (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 108-113 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A pentachlorophenol(PCP)-degrading Pseudomonas sp. strain UG30 was encapsulated in κ-carrageenan for use in PCP degradation. Free and encapsulated cells were compared for their ability to dechlorinate and mineralize 100–800 μg/ml sodium pentachlorophenate in broth. Dechlorination was measured with a chloride ion electrode, and mineralization was measured by 14CO2 evolution from radiolabelled [U-14C]PCP. Free and encapsulated Pseudomonas sp. UG30 cells mineralized up to 200 μg/ml and 600 μg/ml PCP, respectively, after 21 days. Encapsulation of UG30 cells provided a protective effect, allowing dechlorination and mineralization of high levels of PCP to occur.
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    Effect of feed composition and upflow velocity on aggregate characteristics in anaerobic upflow reactors (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 102-107 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Two upflow anaerobic hybrid reactors treated lactose and a mixture of ethanol, propionate and butyrate, respectively, at a volumetric loading rate of 3.7 kg chemical oxygen demand (COD) m−3day−1, a hydraulic retention time of 5 days and a liquid upflow velocity of 0.01 m/h. Under steady-state conditions, the lactose-fed sludge had much higher (20%–100%) specific methanogenic conversion rates than the volatile-fatty acid␣(VFA)/ethanol-fed sludge for all substrates tested, including VFA. In both reactors, a flocculant sludge developed, although a much higher content of extracellular polysaccharide was measured in the lactose-fed sludge [1900 μg compared to 305 μg uronic acid/g volatile suspended solids (VSS)]. When the liquid upflow velocity of a third, VFA/ethanol-fed reactor was increased to 0.5 m/h, granulation of the sludge occurred, accompanied by a large increase (200%–500%) in the specific methanogenic conversion rates for the syntrophic and methanogenic substrates studied. Granulation reduced the susceptibility of the sludge to flotation. Glucose was degraded at a high rate (100 mg glucose gVSS−1h−1) by the sludge from the third reactor, despite not having been exposed to a sugar-containing influent for 563␣days.
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    Saponified palm kernel oil and its major free fatty acids as carbon substrates for the production of polyhydroxyalkanoates in Pseudomonas putida PGA1 (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 207-211 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The synthesis of polyhydroxyalkanoates (PHA) by Pseudomonas putida PGA1, using saponified palm kernel oil (SPKO), was investigated. The PHA produced from SPKO was compared with those produced by the major free fatty acids found in the palm kernel oil. Owing to the absence of lipase activity in P.␣putida, palm kernel oil did not support cell growth. However, SPKO could support cell growth and produced relatively high yield of both dry cells and PHA. The polyester produced was similar in properties to those derived from lauric (C12:0) and myristic (C14:0) acids, while oleic acid (C18:1) gave rise to PHA that was sticky and of broader molecular mass distribution. Nuclear magnetic resonance and gas chromatography showed that these PHA were copolymers consisting mainly of n-alkanoate monomers ranging from C6 to C14, with C8 as the predominant component. PHA derived from SPKO and oleic acid also contained a small amount of unsaturated monomers.
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    A new arabinofuranohydrolase from Bifidobacterium adolescentis able to remove arabinosyl residues from double-substituted xylose units in arabinoxylan (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 231-235 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An arabinofuranohydrolase (AXH-d3) was purified from a cell-free extract of Bifidobacterium adolescentis DSM 20083. The enzyme had a molecular mass of approximately 100 kDa as determined by gel filtration. It displayed maximum activity at pH 6 and 30 °C. Using an arabinoxylan-derived oligosaccharide containing double-substituted xylopyranosyl residues established that the enzyme specifically released terminal arabinofuranosyl residues linked to C-3 of double-substituted xylopyranosyl residues. In addition, this arabinofuranohydrolase released arabinosyl groups from wheat flour arabinoxylan polymer but showed no activity towards p-nitrophenyl α-l-arabinofuranoside or towards sugar-beet arabinan, soy arabinogalactan, arabino-oligosaccharides and arabinogalacto-oligosaccharides.
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    Effect of chlorinated aliphatic hydrocarbons on the acetoclastic methanogenic activity of granular sludge (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 324-328 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The toxicity of chlorinated aliphatic hydrocarbons on acetoclastic methanogens in anaerobic granular sludge was determined using a standardized anaerobic bioassay method. Most of the chloroaliphatics tested were strong inhibitors of methanogenesis. Tri- and tetrachloride derivatives of methane and ethane were the most highly toxic compounds tested, with concentrations of less than 18 mg/l resulting in 50% inhibition (IC50) of the methanogenic activity. Dichlorinated compounds were less toxic, with IC50 values ranging from 40 mg/l to 100 mg/l. On the other hand, perchlorinated derivatives of ethane and ethene were scarcely inhibitory at concentrations near their maximum water solubility. The toxicity caused by chlorinated aliphatic hydrocarbons was reversible. The comparison of structurally related compounds indicated that unsaturated chloroaliphatics were less toxic than their saturated counterparts. A reverse correlation between the electric dipole moment of these compounds and their methanogenic toxicity is discussed.
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    Microbially influenced corrosion of glass (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 337-346 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Microbially influenced corrosion of glass and countermeasures were studied by literature research and by an investigation of contaminated glass samples. Such corrosion is often linked to the growth of fungi. It is assumed that glass composition is not the decisive factor in biogenic contamination, but can encourage or retard the microbial activity significantly. It is suggested that a biochemically initiated ion-exchange reaction is most important for corrosion of glass exposed to the atmosphere. Future work will emphasize the biotechnological applications in the recovery of heavy metals from special glasses.
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    Immobilisation of whole bacterial cells for anaerobic biotransformations (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 352-357 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Anaerobically grown cells of Escherichia coli were immobilised within a range of entrapment matrices and packed into a column under standard conditions, and the ability of the immobilised cells to reduce nitrite (0.5 mM) was measured at a range of flow rates using sodium formate (20 mM) as the electron donor for nitrite reduction. A flow-rate/activity plot was constructed for each flow-through reactor and RA1/2 values (residence time corresponding to 50 % nitrite removal) calculated for each reactor type. Cells immobilised in flat and hollow-fibre membranes were the most effective (RA1/2 = 0.35 h and 0.47 h respectively), with cells entrapped by dialysis membrane (1.53 h), alginate beads (1.93 h), Hypol foam (2.31 h) and polyacrylamide gel (50 % nitrite not removed at maximum residence time tested: 4.9 h) performing progressively less effectively. Cells grown as a biofilm on a range of support materials were also tested in comparable packed-bed reactors. Cell loss from these supports was extensive and contributed to poor performance of the reactors despite high initial biomass loadings (RA1/2 values using raschig rings, coke and activated-carbon supports: 1.6 h, 2.3 h and 1.0 h respectively). Biofilms grown on Pharmacia microcarrier supports and used in packed and also fluidised beds were more stable and the performance of these reactors was superior to that of biofilm reactors using other supports, and comparable to that of the membrane reactors (RA1/2 values for Cytoline 2, Cytopore 2 and Cytodex 3: 0.76 h, 0.56 h, 0.68 h respectively).
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    Efficient production of secreted proteins by Aspergillus : progress, limitations and prospects (1997)
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    Applied microbiology and biotechnology 47 (1997), S. 1-11 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Filamentous fungi are widely used for the production of homologous and heterologous proteins but, compared to homologous proteins, the levels of production of heterologous proteins are usually low. During the last 5 years, the levels of production of heterologous proteins have been drastically improved by fusing the corresponding gene to the 3' end of a homologous gene, encoding a well-secreted protein such as glucoamylase. Nevertheless, little research has been carried out to determine the limitations that hamper heterologous protein production. Recently we have carried out a detailed analysis of the levels of production of several proteins and glucoamylase fusion proteins in defined recombinant Aspergillus awamori strains. In this review we will focus on the use of filamentous fungi for the production of heterologous, especially non-fungal, proteins. In particular, the effect of gene-fusion strategies will be reviewed. Furthermore, the remaining limitations in heterologous protein production and suggestions for improvement strategies for overproduction of these protein will be discussed.
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    Expression of a synthetic protein-based polymer (elastomer) gene in Aspergillus nidulans (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 368-372 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A gene for a synthetic protein-based polymer, G-(VPGVG)119-VPGV, coding for the EG-120mer (elastomer), was cloned into a fungal expression vector to allow constitutive expression of the polymer controlled by the gpdA (glyceraldehyde-3-phosphate dehydrogenase) promoter sequence of Aspergillus nidulans. Stable transformants of A. nidulans showed plasmid integration with varying copy number when analyzed by Southern-blot hybridization. Expression of the synthetic gene was demonstrated by Northern-blot hybridization. However, the translational efficiency for production of the polymer polypeptide was low, presumably because of certain codons in the polymer gene (CCG and GUA) that are rarely used by A. nidulans. Partial purification by reversible phase transition followed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed the presence of polymer protein in a transformant that contained multiple copies of the polymer gene. This study represents the first attempt to express a synthetic gene (with no natural analog) in a fungus.
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    The Propionibacterium freudenreichii hemYHBXRL gene cluster, which encodes enzymes and a regulator involved in the biosynthetic pathway from glutamate to protoheme (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 385-392 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A clone that can complement both Escherichia coli hemB and hemL mutations was found among plasmids containing the Propionibacterium freudenreichii hemB gene, which encodes δ-aminolevulinic acid dehydratase. The regions upstream and downstream of the hemB gene were sequenced. Two open-reading frames (ORF1 and -2), which were similar to the hemY gene encoding protoporphyrinogen oxidase and the hemH gene encoding ferrochelatase from Bacillus subtilis, were found upstream of the hemB gene. ORF1 and -2 complemented the E. coli hemG mutation, defective in protoporphyrinogen oxidase, and the hemH gene respectively. Since ORF1 had no homology to hemG, the gene was designated hemY. The hemYHB genes appeared to be within the same transcription unit. Downstream from the hemB gene, three open-reading frames were found. One of these, transcribed in the same direction as the hemB gene, was identical to be the hemL gene, which encodes glutamate-1-semialdehyde 2,1-aminomutase. The other two open-reading frames, located between the hemYHB and hemL genes, were transcribed divergently, and their deduced amino acid sequences showed similarities to a membrane-bound transport protein and a transcriptional regulatory protein respectively. The two genes may thus be involved in hem transport and the regulation of hem gene expression respectively, and were tentatively named hemX and hemR. Although hemX and hemL are unlikely to be part of the same operon, hemYHBXRL␣are clustered on the P. freudenreichii chromosome.
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    Isolation of freeze-tolerant laboratory strains of Saccharomyces cerevisiae from proline-analogue-resistant mutants (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 405-411 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Since some amino acids, polyols and sugars in cells are thought to be osmoprotectants, we expected that several amino acids might also contribute to enhancing freeze tolerance in yeast cells. In fact, proline and charged amino acids such as glutamate, arginine and lysine showed a marked cryoprotective activity nearly equivalent to that of glycerol or trehalose, both known as major cryoprotectants for Saccharomyces cerevisiae. To investigate the cryoprotective effect of proline on the freezing stress of yeast, we isolated proline-analogue-resistant mutants derived from a proline-non-utilizing strain of S. cerevisiae. When cultured in liquid minimal medium, many mutants showed a prominent increase, two- to approximately tenfold, in cell viability compared to the parent after freezing in the medium at −20 °C for 1 week. Some of the freeze-tolerant mutants were found to accumulate a higher amount of proline, as well as of glutamate and arginine which are involved in proline metabolism. It was also observed that proline-non-utilizer and the freeze-tolerant mutants were able to grow against osmotic stress. These results suggest that the increased flux in the meta-bolic pathway of specific amino acids such as proline is effective for breeding novel freeze-tolerant yeasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050948
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  • 96
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    Controlled secretion into the culture medium of a hybrid -glucanase by Acetobacter methanolicus mediated by the kil gene of Escherichia coli located on a Tn5 -derived transposon (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 530-536 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A Tn5-based transposon bearing the kil gene (killing protein), mediating controlled export of periplasmic proteins into the culture medium, was constructed (Tn5-KIL3). This transposon contained the kil gene of the ColE1 plasmid under the growth-phase-dependent promoter of the fic gene (filamentation induced by cAMP) of Escherichia coli, an interposon located upstream of kil, a kanamycin/neomycin-resistance gene, a multiple cloning site and the mob site. The transposition of Tn5-KIL3 to Acetobacter methanolicus showed a moderate transposition frequency (10−5–10−6). By insertion of a Bacillus hybrid β-glucanase (bgl ) as a model protein into the transposon (Tn5-LF3) it was shown that the secretion function as well as the gene of the target protein had been transferred to and stably integrated into the chromosome of A. methanolicus, and that the transposition of Tn5-LF3 was non-specific. β-Glucanase was highly overexpressed and secreted into the medium during stationary phase. Total and extracellular production of β-glucanase varied depending on the integration site of the transposon. The viability of the bacterial cells was not affected, and cell lysis did not occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050968
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  • 97
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    Electronic Resource
    Metabolic response of Bacillus sphaericus 1593M for dual-substrate limitation in continuous and total-cell-retention cultures (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 554-559 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A chemically defined medium has been developed to support the growth and the production of mosquito larvicidal factor(s) (MLF) of Bacillus sphaericus 1593M. On the basis of the data of steady-state continuous cultures, it has been understood that acetate can serve as a sole carbon and energy source for B. sphaericus 1593M. Utilization of acetate by B. sphaer-icus 1593M and the production of MLF are further enhanced by the addition of glutamate at low concentrations, both in steady-state continuous as well as in total-cell-retention cultures (TCRC). A two-step TCRC procedure resulted in better biomass and MLF production by B. sphaericus 1593M. It was also found that glutamate can serve as a carbon source as well as a growth factor in the presence of acetate and hence is a partially substitutable carbon source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050972
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  • 98
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    Electronic Resource
    Cell-linked and extracellular cholesterol oxidase activities from Rhodococcus erythropolis. Isolation and physiological characterization (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 583-589 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Rhodococcus erythropolis cells growing in a cholesterol-free glycerol-containing mineral medium displayed very low levels of a cell-wall-bound cholesterol oxidase activity. Addition of cholesterol induced a marked increase in the synthesis of this enzyme, which reached a maximum within 6 days and was subsequently followed by the appearance of extracellular cholesterol oxidase in the culture broth. Significant levels of induction were only achieved when cholesterol emulsified with Tween 80. The presence of chloramphenicol at the time of induction completely prevented the emergence of both enzymatic forms, suggesting the requirement of de novo protein synthesis. Upon transfer of cholesterol-growing cultures to fresh medium lacking cholesterol, the extracellular cholesterol oxidase was quickly erased, while the activity of the particulate enzyme decreased sharply. The electrophoretic pattern on native Western blotting as well as on sodium dodecyl sulphate/polyacrylamide gels, together with kinetic data, strongly support the idea that the particulate and extracellular cholesterol oxidases are two different forms of the same enzyme with an estimated molecular mass of 55 kDa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050977
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  • 99
    Electronic Resource
    Electronic Resource
    Simultaneous consumption of glucose and fructose from sugar mixtures during batch growth of Corynebacterium glutamicum (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 600-603 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Growth of Corynebacterium glutamicum on mixtures of glucose and fructose leads to simultaneous consumption of both sugars in which the uptake of each sugar is directly related to the expression of the corresponding sugar uptake mechanism. The overall rate of sugar uptake was higher on sugar mixtures than on either glucose or fructose alone and was similar to that observed during sucrose metabolism. The results suggest that sugar uptake limits metabolic rates though, in the case of fructose, overflow metabolism of both lactate and dihydroxyacetone was observed. Such products could reflect a higher flux through glycolysis rather than the pentose pathway during catabolism of fructose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050980
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  • 100
    Electronic Resource
    Electronic Resource
    Enhanced oily sludge biodegradation by a tensio-active agent isolated from Pseudomonas aeruginosa USB-CS1 (1997)
    Springer
    Applied microbiology and biotechnology 47 (1997), S. 615-619 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The biodegradation of an oily sludge is facilitated by a microbial tensio-active agent isolated from Pseudomonas aeruginosa USB-CS1. The optimal oil-in-water dispersion conditions are as follows: pH 6.5, temperature 30 °C, agitation 150 rev/min. The total hydrocarbon content shows that the biodegradation of the oily substrate mediated by the biosurfactant or by the biosurfactant–P. aeruginosa USB-CS1 complex is significantly higher after 30 days of incubation than that in other experimental conditions, by a mean of 70%. Substrate fractionation by column chromatography reveals that, if biosurfactant is present, saturated and aromatic compounds are more susceptible to microbial degradation than they are in other biodegradation systems by an average of 55% and 40% respectively. These results suggest that the stimulatory effects of the biosurfactant on the biodegradation of the oily substrate are limited over time by the loss of surface activity of the biosurfactant after 30 days of incubation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050983
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