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  • Articles  (8,527)
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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.
    Type of Medium: Electronic Resource
    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.
    Type of Medium: Electronic Resource
    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.
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    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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    URL: http://dx.doi.org/10.1023/A:1018483722417
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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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    URL: http://dx.doi.org/10.1023/A:1018415201945
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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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    URL: http://dx.doi.org/10.1023/A:1018404426960
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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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  • 45
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    Swelling of carboxymethylated cellulose fibres (1997)
    Springer
    Cellulose 4 (1997), S. 293-303 
    Details
    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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    URL: http://dx.doi.org/10.1023/A:1018400226052
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    Isolation and characterization of a methanol utilizing yeast with high cell yield (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 19-23 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A yeast (Pichia pastoris strain CMB 10) growing on methanol as sole carbon and energy source was isolated. The high growth rate (0.235·h−1 at pH 5) and high cell yield (0.41 g cell per g methanol at pH 3.5) of this strain are of interest for production of single cell protein (SCP). Other advantages of the strain are: low maintenance coefficient (m=9.5 mg·g−1·h−1), high affinity for methanol (Ks=100 mg·l−1), possibility of non aseptic culture at low pH (pH 3.5), equilibrated amino acid profile and flocculating properties.
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    URL: http://dx.doi.org/10.1007/BF00510566
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  • 47
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    Kinetic aspects of glucose oxidation by Gluconobacter oxydans cells immobilized in calcium alginate (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 13-18 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Gluconobacter oxydans subspecies suboxydans (ATCC 621 H), when growing at high glucose concentrations, oxidizes this substrate incompletely and gluconic acid accumulates in the medium in almost stoichiometric amounts. Such cells were harvested and entrapped in various alginate gels. The preparation with the highest retention of glucose oxidizing activity was used in further studies with the aim of developing an efficient process for continuous gluconic acid production. The retention of activity increases (up to 95%) as the alginate concentration in the gel decreases or the cell/alginate weight ratio is enhanced. In the latter case, however, transport of oxygen to and inside the biocatalyst beads rapidly becomes rate-limiting and thus lowers the efficiency of the biocatalyst. Similarly, the efficiency decreases as the size of the biocatalyst beads increases. In no case rate-limitation by transport of glucose was found. Thus, biocatalyst activity per unit volume of support, diameter of the biocatalyst beads, and aeration efficiency are important parameters for reactor design.
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    The effect of high ethanol and CO2 concentrations on the ultrastructure of Zymomonas mobilis (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 44-48 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Zymomonas mobilis cells were examined by electronmicroscopy at various stages of fed-batch cultivation. Using the agar-diffusion method, significant changes in the morphology were observed under low glucose and increasing ethanol and CO2 concentrations. High concentrations of these products cause the appearance of extensive slime and granular layers around the cells. The reasons for and the possible implications of the observed changes in ultrastructure on industrial ethanol production are discussed in view of the presently experienced limitations in product formation.
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    The rapid purification of lactate dehydrogenase from alcaligenes eutrophus in a two-step procedure (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 163-167 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A NAD-linked L(+)-lactate dehydrogenase (EC 1.1.1.27) was isolated from Alcaligenes eutrophus N9A. During purification advantage was taken of the high affinity of MatrexTM Gel Green A for this enzyme in crude extracts. One ml of this medium adsorbed 2660 U lactate dehydrogenase if 129 ml crude extract containing 2,480 mg protein were applied onto the column, as determined by frontal analysis. The enzyme was purified 275-fold by chromatography on this medium. Subsequent chromatography on Cibacron Blue F3G-A Sepharose 6B-CL resulted in a 3-fold purification and in a homogeneous preparation of lactate dehydrogenase. Starting with a crude extract containing 12 g total protein, the overall purification factor was 712.5, corresponding to a recovery of 36.1% activity and a specific activity of 776.6 U/mg protein. The affinity of MatrexTM Gel Green A medium to lactate dehydrogenase from other sources like A. hydrogenophilus, A. eutrophus A7, A. faecalis, Escherichia coli, Lactobacillus lechmannii, and rabbit muscle was investigated. Advantages of this method for large scale purification of lactate dehydrogenase from Alcaligenes eutrophus are discussed and compared to large scale purification methods applied for other enzymes.
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    Determination of ATP from compost using the firefly bioluminescence technique (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 187-190 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A convenient method for extraction and bioluminescence determination of adenosine triphosphate (ATP) from sewage sludge compost was developed and the method was applied to monitore biomass changes during a laboratory scale composting process. Several extraction methods for ATP were tested. Quartz sand grinding in porcelain mortar with 20% (w/v) trichloroacetic acid appeared to be the best one. In the laboratory scale experiment the ATP concentration correlated with the temperature and pH. After a lag-period of about 20 h the ATP concentration increased from about 15 μg/g (dry weight) to 30 μg/g until mesophilic temperatures were exceeded. In the beginning of the thermophilic stage the ATP concentration decreased steeply to about 10 μg/g and was slowly restored to about 20 μg/g during the thermophilic phase. When the temperature approached the ambient level the ATP concentration decreased coincidently with temperature to about 10 μg/g.
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    The effect of glucose on 11β- and 19-hydroxylation of reichstein's substance S by Pellicularia filamentosa (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 211-215 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Experiments in batch-fermenters have demonstrated that the 11β- and 19-hydroxylation of Reichstein's Substance S by Pellicularia filamentosa ceases in the absence of glucose. The effects of glucose consumption rate and growth rate on hydroxylation have been investigated using chemostat cultures. With glucose-limited cultures, increased hydroxylation rates were observed with increased glucose consumption rates. With nitrogen-limited cultures, however, some form of glucose-repression exists. The maximum rate of hydroxylation occurred at a glucose consumption rate at which the culture was just nitrogen-limited. The growth rate had no major importance.
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    9α-Hydroxylation of 4-androstene-3,17-dione by gel-entrapped Corynebacterium sp. cells (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 203-210 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Whole cells of Corynebacterium sp. having steroid 9α-hydroxylation system were immobilized by entrapment with photo-crosslinkable resin prepolymers, urethane prepolymers or several kinds of polysaccharides. Of various entrapment methods tested, cells entrapped in photo-crosslinked gels showed the highest activity to hydroxylate 4-androstene-3,17-dione at 9α-position. The properties of the photo-crosslinkable resin prepolymers, such as the hydrophobicity and the chain length of the prepolymers, affected markedly the activity of the entrapped cells. Addition of dimethyl sulfoxide to a buffer system at 15 vol. % was effective to solubilize the product, 9α-hydroxy-4-androstene-3,17-dione, and gave the highest yield. In an aqueous system, the activity of hydrophilic gel-entrapped cells was higher than that of hydrophobic gel-entrapped cells. In 15% of dimethyl sulfoxide, the hydrophobic gel-entrapped cells showed almost the same activity as the hydrophilic gel-entrapped cells probably due to extraction of the product from gels to the external solvent before its metabolic degradation. Entrapment significantly enhanced the conversion ratio at high substrate concentrations and the operational stability of the 9α-hydroxylation system in the cells. In the presence of nutrients in the reaction mixture, entrapped growing cells maintained fully the original activity at least during 10 times of repeated batch reactions for 5 days.
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    Limitations of HPLC for the detection of β-exotoxin in culture filtrates of Bacillus thuringiensis (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 231-234 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary High performance liquid chromatography (HPLC) was used to detect and quantify β-exotoxin, a phosphorylated adenine nucleotide derivative produced as an excreted metabolite by several strains of Bacillus thuringiensis. The assay was rapid and quantitative for purified β-exotoxin standards. However, peak height failed to correlate β-exotoxin concentration in crude culture filtrates with biological activity toward house fly larvae. Unrelated compounds (from non-β-exotoxin producers) co-eluted with β-exotoxin, thereby making the technique an unreliable method for toxin detection and quantification.
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    The use of Aspergillus niger for bioconversion of apple distillery waste (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 243-247 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The bioconversion of waste material remaining after apple brandy distillation was investigated. Different cellulolytic fungi were tested for their ability to convert the waste organic substances into microbial biomass. An Aspergillus niger strain was chosen as the most convenient microorganism. By growing this mold on the apple slop the following results were obtained: filtration time was shortened by 30 times, reduction of the chemical oxygen demand in the liquid phase in the range of 50–80% depending on the substrate dilution and a dry filter cake enriched with fungal biomass to about 12 g/l containing up to 22% raw proteins and certain amounts of cellulolytic enzymes in the filtrate. The influence of the initial pH, the salt addition and the dilution of the substrate were studied as well.
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    Mixed culture of Saccharomycopsis fibuliger and Zymomonas mobilis on starch-use of oxygen as a regulator (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 269-274 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The conversion of starch to ethanol in a mixed culture of an amylolytic yeast, Saccharomycopsis fibuliger and an anaerobic bacterium, Zymomonas mobilis, was studied. Interactions between the component cultures were commensalism and competition for glucose. Control of oxygen supply to the culture was used as an external regulator of growth and competition. No accumulation of reducing sugars was observed in the mixed culture when compared to a monoculture of Saccharomycopsis fibuliger grown on starch. The glucose formed was instantly used by Zymomonas mobilis for ethanol production and the glucose inhibition of hydrolysis of non-glucose reducting sugars was released. The final concentration of ethanol, 9.7 g·l−1, produced from 30 g·l−1 of starch, shows out that all the glucose available from starch hydrolysis was converted to ethanol. Glucose production from starch was the rate-limiting reaction in the system, causing a lower ethanol production rate in the mixed culture than in the monoculture of Zymomonas mobilis, grown on glucose.
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    Fermentation of xylose with the yeast Pachysolen tannophilus (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 287-291 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Pachysolen tannophilus IfGB 0101, is able to grow aerobically on xylose, glucose and fructose. Galactose too is assimilated after long adaption times. In the complete absence of oxygen, xylose is fermented, forming mainly xylitol, lower amounts of ethanol and CO2. According to the mass balance, it may be concluded that the pentose phosphate enzymes together with the oxidative phosphogluconate way are in action simultaneously. At semi-aerobic conditions (0.45 l air per liter, per hour) ethanol production is somewhat increased but no aeration conditions could as yet be found at which ethanol was the main fermentation product. The significance of xylitol formation seems to be mainly that of an electron sink of the phosphogluconate pathway.
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    Characterization of cellulases by HPLC separation (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 314-318 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The proteins in the supernatant of Trichoderma reesei were separated by HPLC and exo-, endo-β 1,4-glucanase, and β-glucosidase activities for the various fractions obtained were measured. Bovine serum albumin (BSA), chymotrypsin, β-glucosidase, endoglucanase and other cellulase preparates were used as reference substrates.
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    The effect of carboxymethyl-cellulose addition on extracellular enzyme formation in Trichoderma pseudokoningii (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 339-343 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The addition of carboxymethyl-cellulose (CMC) to a medium containing crystalline cellulose (avicel) as a carbon source resulted in increased production of β-glucosidase (up to 6-fold) and exo-β-1,3-glucanase (12-fold) by Trichoderma pseudokoningii. Less pronounced stimulation of production was observed for laminarinase (2-fold) and mannanase (2-fold), whereas other enzymes (filter-paper activity, amylase, amyloglucosidase, acid phosphatase and N-acetyl-glucosaminidase) were only insignificantly influenced. In the case of β-glucosidase, the effect depended on the presence of high (2%, w/v) concentrations of cellulose and 0.2% (w/v) peptone. The stimulating effect of CMC was not observed when lactose was used as a carbon source. CMC could not relieve β-glucosidase from repression by glucose.
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    Isolation and partial characterization of large plasmids in hydrogen-evolving bacterium Clostridium butyricum (1983)
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 349-354 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The hydrogen-evolving bacterium Clostridium butyricum IFO 3847 was found to carry three plasmids: pSSK1, pSSK2, and pSSK3. The molecular weights of pSSK1, 2 and 3, determined by agarose gel electrophoresis and electron microscopy, were about 51, 32, and 9.4 megadaltons respectively. The two larger plasmids were analysed by digestion with several restriction enzymes such as AvaII, BamHl, EcoRl, Pst1, and Sall. With each enzyme, 10–20 fragments were produced from pSSK1 and five to six fragments from pSSK2. Since in each digestion some fragments were common to both plasmids, the two plasmids pSSK1 and pSSK2 must be related to each other to a high degree. The other small plasmid pSSK3 was digested by restriction endonucleases, EcoR1, Pst1, and Sall at single sites, so that this plasmid might be a candidate as a vector for gene cloning in Clostridium species.
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    Effect of glucose analogues on synthesis of sugar nucleotides and oligosaccharides inSaccharomyces cerevisiae (1975)
    Springer
    Applied microbiology and biotechnology 1 (1975), S. 41-54 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In a special standard reaction system with active dried yeast as an enzyme source about 65% of added 5′-UMP was transformed into UDPG. In this system 2-deoxyglucose was not only demonstrated to be a substrate for yeast hexokinase, but was also shown to enter the “LELOIR-pathway”. Depending upon the ratio of glucose to glucose-analogue, 2-deoxyglucose was incorporated into uridine-sugar-nucleotides, deoxy- and dideoxytrahalose. The trahalose splitting enzyme, trehalase (EC 3.2.1.28) showed a different substrate specifity towards trehalose and its unnatural analogues. Although 2-deoxy-2-chloro-D-glucose and 2-deoxy-2-fluoro-D-glucose were good substrates for yeast hexokinase, these two deoxyhalogenglucopyranoses were not substrates for sugar-nucleotide and trehalose synthesis. 3-O-methylglucose was not phosphorylated and showed no influence on the course of reaction in the in vitro system.
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    Scopulariopsis brevicaulis: Effect of pH and substrate on growth (1975)
    Springer
    Applied microbiology and biotechnology 1 (1975), S. 55-66 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Scopulariopsis brevicaulis Bainier NRRL 5867, isolated from ammonia-treated corn during preservation studies, was grown in shaken and still liquid cultures on Blakeslee's malt extract. The medium was adjusted to different pH values between 5.0 and 10.6 with sodium hydroxide and ammonium hydroxide. Maximum mycelium was produced at an initial pH of 9.0–10.0. Considerably more mycelium was produced in shaken flasks than in still cultures. When the initial pH was adjusted to 10.0 with ammonium hydroxide, 1350 mg mycelium/200 ml Blakeslee's malt extract was produced in contrast to 540 mg with sodium hydroxide. Approximately 28% of the total solids and 25% of the nitrogen in an ammoniated corn infusion broth were converted to mold mycelium high in essential amino acids and protein by both NRRL 5867 and NRRL 3273, another strain ofS. brevicaulis. WhenS. brevicaulis was grown 7 days on a solid substrate of ammoniated corn, ammonia was converted to organic material, carbohydrate was utilized and the protein of the fermented corn increased in lysine and methionine. Approximately 9% of the weight of the corn was lost during the process.
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    URL: http://dx.doi.org/10.1007/BF01880620
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    Production ofl-tryptophan,l-tyrosine and their analogues by use of immobilized tryptophanase and immobilizedβ-tyrosinase (1975)
    Springer
    Applied microbiology and biotechnology 1 (1975), S. 25-39 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Production of L-tryptophan, L-tyrosine, or their analogues was attempted using immobilized tryptophanase or β-tyrosinase. The immobilized tryptophanase used in this study was first prepared by the present authors by coupling of free apoenzyme fromEscherichia coli B/1t-7A to pyridoxal 5′-phosphate (PLP) previously bound on Sepharose. This immobilization method involves the formation of Schiff base linkage between 4-formyl group of Sepharose-bound PLP and the α-amino group of the lysine residue of the catalytic center of one subunit of tetrameric apotryptophanase, followed by reductive fixation of the Schiff base linkage with NaBH4. In the case of β-tyrosinase fromEscherichia intermedia having two catalytic centers, however, immobilization by direct coupling to CNBr-activated Sepharose or a bromoacetyl derivative of Sepharose was more suitable than by the coupling to Sepharose-bound PLP. In each case, the affinity for substrate or coenzyme was scarcely affected by the immobilization. The immobilized enzymes thus obtained were shown to possess higher thermal stability and higher resistance to denaturing agents than the free counterparts. The optimal temperature for a short time reaction (10 min) was ca. 70°C for immobilized tryptophanase or 55°C for immobilized β-tyrosinase. In each case the optimal reaction temperature mediated by the immobilized enzyme was fairly higher than that catalyzed by the respective free enzyme. Addition of ethanol (5%, V/V) to the reaction mixtures favored the tryptophanase and β-tyrosinase reactions. The equilibrium of α, β-elimination reactions of L-tryptophan and β-tyrosine lied so far to the synthetic side (70% in tryptophanase and 80% in β-tyrosinase reactions, respectively). By continuous flow methods using these immobilized enzyme columns, L-tryptophan, L-tyrosine, and their analogues, such as L-DOPA and L-5-hydroxytryptophan, were conveniently synthesized in good yields.
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    Parameters affecting protein production from brewery waste water in a multi-channel laboratory-scale activated sludge system (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 52-59 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary With the aim of studying the possible utilization of brewery waste water activated sludge for animal feeding, the influence of the solids retention time (SRT) and nitrogen supplementation were investigated, especially with respect to biomass production and biomass composition. It was found that the SRT strongly influenced both parameters. At an SRT of from 4 to 6 days excellent biomass production was obtained. This biomass had the highest protein content and the daily protein production was four times higher than at a SRT of 20 days. Supplementation with urea doubled the protein production, lowered the carbohydrate and poly-β-hydroxybutyric acid content, but increased the nucleic acid content. The COD removal was better and phosphorus removal increased. In order to study these variables, a multi-channel laboratory system was designed. Because of its simplicity in operation and its versatility this system is described in detail.
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    URL: http://dx.doi.org/10.1007/BF00508129
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    Large scale production of d-lactate dehydrogenase for the stereospecific reduction of pyruvate and phenylpyruvate (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 75-85 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary To initiate studies of the stereospecific reduction of pyruvate and phenylpyruvate to the corresponding d-2-hydroxyacids a limited screening was carried out for microorganisms possessing a high NADH-dependet d-lactate dehydrogenase activity. Lactobacillus confusus was found to produce the desired dehydrogenase, which showed also relatively high activity towards phenylpyruvate, so this strain was selected for large scale production of the enzyme. A procedure for large scale purification of the enzyme starting with 24 kg wet cells is described including liquid-liquid extraction, ultrafiltration and chromatography on DEAE-cellulose, yielding a catalyst with specific activities of 216 U×mg−1 for pyruvate reduction and 15 U×mg−1 for phenyl-pyruvate reduction. A further tenfold purification can be achieved by affinity chromatography on Blue-Sepharose C-6B. Parameters which are important for industrial application of the enzyme were determined: substrate specifity, pH and temperature optimum, temperature stability, stability at different pH-values, and the storage stability of the enzyme in crude extracts.
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    URL: http://dx.doi.org/10.1007/BF00500828
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    Incorporation of [14C]acetate into aflatoxin by resting cultures of Aspergillus parasiticus in the presence of antifungal agents (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 103-108 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Resting cultures of Aspergillus parasiticus were treated with sorbic acid (200 ppm), Nα-palmitoyl-l-lysyl-l-lysine ethyl ester dihydrochloride (PLL) (300 ppm), nisin (30 ppm), nystatin (30 U/ml), dichlorvos (9 ppm), butylated hydroxyanisole (BHA) (30 ppm) and isoprothiolane (30 ppm). Incorporation of [14C]acetate into aflatoxins B1 and G1 by the mold in the presence of these antifungal agents was measured after 12 h of agitated incubation at 28°C. Nystatin and BHA effectively inhibited incorporation of the label into aflatoxin B1 (73.1 and 56.9%) and G1 (68.9 and 91.6%), respectively, whereas PLL and nisin, at the levels used, were less effective. Sorbic acid caused greater inhibition of de novo synthesis of aflatoxin B1 than of G1 while isoprothiolane exhibited the opposite effect. Because the compounds tested had dissimilar physical, chemical and antimicrobial properties, it is likely that they inhibited synthesis of aflatoxin by different mechanisms. Generally, inhibition of aflatoxin synthesis by the test chemicals under resting conditions was more pronounced than what was reported earlier when the same chemicals (at the same levels) were tested with growing cultures of the mold.
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    Induction and stabilization of l-phenylalanine ammonia-lyase activity in Rhodotorula glutinis (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 158-162 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary l-Phenylalanine ammonia-lyase (PAL) activity in Rhodotorula glutinis IFO 0559 cells was induced by the addition of 0.5% l-phenylalanine. Activities as high as 15.0×10−3 U/mg of cells were obtained. The activity reached a maximum after about 6 h of induction, and then diminished gradually. The enzyme was also induced by d-phenylalanine, l-isoleucine, d-isoleucine, l-leucine, d-leucine, l-valine, l-methionine, l-tryptophan, and l-tyrosine. When 0.1% l-isoleucine was added, high PAL activity was sustained for a relatively long time, but the maximum activity was not increased. Particularly when l-isoleucine and l-valine or l-isoleucine and d-leucine were used as inducers, enzyme activities as high as 22.7 or 24.6×10−3 U/mg of cells respectively were obtained. Since the induction of PAL activity by various amino acids was inhibited completely by 50 μM cycloheximide, the induction process was considered to involve de novo synthesis of the enzyme protein.
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    The application of enzyme activity measurements to a study of factors affecting protein, starch and cellulose fermentation in domestic refuse (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 181-185 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Analysis indicated cellulose to be the principal component of unfermented domestic refuse and the cellulose: lignin ratio to be a constant value of 3.5∶1. Extracellular enzyme determinations were found to be suitable for assessing microbial activity in fermenting refuse but not for quantifying rates of polymer hydrolysis. Initial stages of fermentation were associated with the breakdown of protein and starch. Cellulase activity was low, possibly due to the destructive effect of proteases, and lipases were not detected. Protease and amylase activities were significantly affected by refuse moisture content, and changes in enzyme activities did not correlate with most probable number determinations (mpn) of the different physiological groups.
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    Continuous ethanol production by cell-holding culture of yeasts (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 201-206 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A new apparatus for continuous ethanol production with internal separation of yeast cells is described. The removal of cell-free medium is accomplished by cake filtration through a thin layer of diatomaceous earth. By using a feeding pump connected with a level meter, fresh medium is supplied at the same rate at which the culture solution filtered off. Continuous operation with stepwise increases in glucose concentration in the feed medium resulted in steady states of cell density in accordance with the glucose concentration in the medium. A high density of yeast cells, more than 109/ml of culture broth, was maintained in the reactor with a loss of cells of the order of 104–105 during continuous filtration. Maximum ethanol productivity obtained in this cell-holding culture of commercial baker's yeast was 26 g/l/h when 10% glucose was supplied with a retention time of 1.7 h. The ethanol productivity in continuous operation was increased in proportion to the glucose concentration in the feed medium when growing Saccharomyces cerevisiae IFO 2363 cells were used. At any given glucose concentration, the conversion rate of glucose to ethanol achieved was 96% of the maximum theoretically obtainable.
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    Phanerochaete chrysosporium: Growth pattern and lignin degradation (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 153-157 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The growth behavior of Phanerochaete chrysosporium was characterized in a bioreactor using chemostat and batch cultivation to optimize an inoculum for lignin degradation during stationary cultivation. The pattern of growth and onset of lignin degradation by cells taken from agitated conditions were compared to the behavior of cells grown under stationary conditions. Under nitrogen-limited growth conditions, the fungus displayed a continuous growth-rest-growth cycle, as visually observed and evidenced by changes in total cell carbohydrate and biomass content, indicating recycling of cell nitrogen. Cells taken from the bioreactor degraded lignin only after a mycelial mat was formed under non-agitated conditions. Formation of the mat occurred during completion of primary growth with cells taken at a dilution rate of 0.09 or 0.10 h−1 and with cells from a 1-day-old batch cultivation, resulting in an onset of lignin degradation after 2–3 days. Cells taken at dilution rates 〈0.09 h−1 formed the mycelial mat as a result of their secondary growth phase. The onset of this mat formation was related to the average age of the cells. Two- to four-day-old cells from the batch cultivation needed 7–9 days before they started to degrade lignin. The glucose consumption rate in the bioreactor during secondary metabolism was 0.09 g · l−1 · day−1, compared to 1.0 g · l−1 · day−1 under non-agitated conditions. This difference is discussed in reference to lignin degradation.
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    Bacterial diversity in thermophilic aerobic sewage sludge (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 174-180 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Over a 2-year period thermophilic microorganisms were isolated from an aerobic thermophilic, continuously operated sewage sludge treatment process (Altenrhein SG, CH). A representative set of isolates was characterized for microbiological and biochemical properties and compared with thermophilic reference strains. At least 95% of the isolates were characterized as extremely thermophilic Bacilli with a maximal growth temperature 〉70° C. The other 5% were not finally designated as Bacilli only because sporulation could never be demonstrated. The thermophilic microflora did not produce antimicrobial substances in detectable amounts. All isolates grew rapidly (μmax ranging from 0.7 to 2.2 h−1) on sucrose medium in shake flasks with generally low yields (Y ranging from 0.2 to 0.3 g·g−1). More than 90% of the isolates could degrade casein and starch and grew on gummi arabicum as sole carbon source. Amylases and proteases were formed in cheap, complex compounds containing media but not in significant amounts in growth media containing simple carbon sources.
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    Development of a small scale mashing and fermentation system for studies on malt whisky production (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 207-213 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A technique has been developed to produce up to 101 of fresh wort in laboratory conditions for use in small scale whisky fermentations. Neither boiled or sterilised wort can be used for this process. Using this wort experiments have been carried out to investigate the physiology of the malt whisky fermentation. The fermentation was found to have an initial acceleration phase, a linear phase and a decline phase. The level of higher alcohols, fatty acids and esters was measured at different stages of the fermentation using a carbon disulphide extract of the cell free wash to prepare the samples for GLC analysis. The formation of the higher alcohols follows the same pattern as ethanol, as did the acetate esters of higher alcohols. However medium chain fatty acids and their ethyl esters were produced throughout the fermentation.
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    Fermentative production of ethylene by Penicillium digitatum from citrus fruit peel (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 293-297 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Fermentative conditions for the production of ethylene by the fungus Penicillium digitatum during its growth on citrus fruit peel — the waste product of the citrus juice industry — were studied and optimized for maximum production. Different isolates of the fungus differed markedly in their ability to produce ethylene in liquid culture or when incubated on fruit and fruit peel. Production rates in a low phosphate-chemically defined medium ranged from 0 to 5 μl/g of fungal fresh weight/h. Rates of ethylene production by inoculated citrus peel homogenates ranged from 4 to 20 nl/g fresh weight of the peel/h. These rates could be increased not only by selecting a high ethylene producing fungal isolate but also by cutting the peel tissue prior to inoculation for higher surface area, by inoculating the tissue with blended mycelium and by incubating it in the dark. Each of these factors increased the rate of ethylene production to approximately 60 nl/g/h. The optimal temperature of incubation was 25°C. Addition of fruit juice to the inoculated peel homogenate increased by 100 times the rate of ethylene production. Also, the addition of various waste materials, obtained from processing of citrus juice, yeast, starch and alcohol, each increased ethylene production by a factor of 4.5–5. Our data indicated that production of ethylene by P. digitatum grown on citrus peel tissue could be substantially increased.
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    Biodegradation of non-ionic dispersants in sea-water (1983)
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    Applied microbiology and biotechnology 18 (1983), S. 315-319 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In this paper, we describe the aerobic biodegradation of some non-ionic dispersants of the Span, Tween, and Corexit series in sea-water, where they are now more frequently found as a result of their application to the removal of oil spills. First, the extent to which dispersants are biodegraded, as an indication of their suitability for use on a large scale, is discussed. Biodegradation may be carried out by means of monocultures or mixed cultures of marine bacteria of the genera Aeromonas, Pseudomonas, and Flavobacterium. Analytical techniques based on absorbance measurements were used to follow the process. On the other hand, by determining the kinetics of the biodegradation process a more complete analysis is obtained. The kinetic coefficients controlling the process are deduced and it is shown that for some dispersants the experimental results are in close agreement with the proposed scheme. Where observed values are explained on the basis of ethylene oxides content of the dispersants, estimations of the amount of dispersant present in the sea at a given time can be made, if the amount of the dispersant first used is known.
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    Level of enzymes involved in acetate, butyrate, acetone and butanol formation by Clostridium acetobutylicum (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 327-332 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Clostridium acetobutylicum cells were collected from chemostats which were run at pH 4.3 or 6.0 and which produced either acetone-butanol or acetate-butyrate; they were used to determine the level of enzymes involved either in solvent or in acid formation. The highest activity of phosphotransacetylase, phosphotransbutyrylase, acetate kinase, and butyrate kinase was found in cells which carried out an acetate-butyrate fermentation; these enzymes were present in solvent-producing cells at a level of about 10–50% as compared to acid-producing cells. Hydrogenase activity was detectable in approximately the same amounts in both cell types; however, in solvent-producing cells it was only measurable following a lag-period. Butyraldehyde and butanol dehydrogenases were found in small amounts exclusively in solvent-producing cells. It was demonstrated that the formation of acetone was initiated by the action of a coenzyme A-transferase which transferred coenzyme A from acetoacetyl-CoA to either acetate or butyrate. This coenzyme A-transferase as well as acetoacetate decarboxylase were hardly detectable in acid-producing cells, but reached high levels in solvent producing cells. Similar changes of the activity of the enzymes mentioned were observed when a batch culture was shifted from acid to solvent formation.
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    Pretreatment of wheat straw by white-rot fungi for enzymic saccharification of cellulose (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 350-357 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Of 19 white-rot fungi tested, Pleurotus ostreatus, Pleurotus sp. 535, Pycnoporus cinnabarinus 115 and Ischnoderma benzoinum 108 increased the susceptibility of straw to enzymic saccharification, thus indicating that these organisms degraded or modified the lignin component. After pretreatment cultivation with Pycnoporus cinnabarinus 115, as much as 54.6% of the residue was converted to reducing sugars in the enzymic saccharification process. Phanerochaete sordida 37, Phlebia radiata 79 and two unidentified fungi also gave better results than Polyporus versicolor, a non-selective reference fungus. After 5 weeks pretreatment with Pleurotus ostreatus, 35% of the original straw was convertable to reducing sugars, 74% of which was glucose; compared with this, only 12% of the untreated control straw was convertable to reducing sugars, 42% of which was glucose. After an alkali pretreatment (2% NaOH, 0.4 g NaOH/g straw, 10 min at 115°C) enzymic saccharification converted 41% of the straw to reducing sugars, of which only 50% was glucose. In the best cases the efficiency of biological pretreatment was comparable with that of alkali treatment, but resulted in a higher proportion of glucose in the hydrolysates. Pretreatment by the fungi Phanerochaete sordida 37 and Pycnoporus cinnabarinus 115 in an oxygen atmosphere reduced the treatment time by approximately 1 week. However, the economic feasibility of a non-optimized biological pretreatment process is still poor due to the long cultivation times required.
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    Responses of dairy cows to dietary aflatoxin: Concentration of blood serum constituents and hormones associated with liver-kidney dysfunction and maintenance of lactation (1983)
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 381-386 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary In the first part of this study, two fistulated Holstein cows in mid-lactation were given 13 mg of impure aflatoxin B1 (AFB1) (aflatoxin B1 plus other aflatoxins and metabolites produced by Aspergillus parasiticus in culture) for 7 days. Animals were bled daily and their blood was analyzed for serum glutamate-oxaloacetate transaminase, serum glutamate-pyruvate transaminase, alkaline phosphatase, gamma-glutamyl transpeptidase, bilirubin, cholesterol, triglycerides, total protein, blood urea nitrogen, creatinine, and uric acid. Concentrations of these constituents remained relatively unchanged during treatment. In the second part of the study, seven fistulated Holstein cows in mid-lactation were given daily doses of 13 mg of AFB1 for 7 days. Six animals received pure AFB1; one animal received impure AFB1. Amounts of four hormones [cortisol, insulin, thyroxine (T4), and triiodothyronine (T3)], hormone binding capacity for T3 (T3U), and glucose in serum were monitored. The amount of T3 and percent of T3U increased (12%) and decreased (4%), respectively, during treatment. No discernible changes in amounts of T4, cortisol, insulin, and glucose were observed in the animals receiving pure AFB1. However, glucose levels in serum of the animal receiving impure AFB1 decreased by 9% during treatment. This decrease in serum glucose level was accompanied by a reduction in the amount of milk produced. Overt signs indicative of ill-health were not apparent, and thus could not be related to changes in blood constituents measured.
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    Optimized extracellular production of alkaline phosphatase by lky mutants of Escherichia coli K12 (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 5-12 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Periplasmic-leaky (lky) Hfr mutant strains of Escherichia coli K12, grown in low-phosphate Tris medium, excreted alkaline phosphatase (AP) into the extracellular fluid. The lky207 mutation, which proved to induce the highest AP excretion rate, was transferred to an F- host, carrying a phoS, T mutation allowing constitutive AP biosynthesis. Use of high-phosphate LB-rich medium for growing this F- lky strain improved cell biomass, extracellular AP activity and excretion specificity in favour of the enzyme. Physiological studies helped us to develop a new culture medium (LB 8.3) giving higher enzyme and excretion yields. LB 8.3 medium also increased cell viability of lky mutants stored at 4° C. Using optimized culture conditions, the highest extracellular enzyme activity produced by lky mutant 706 was reached in the late stationary growth phase and was equal to 1,400 U/ml of culture medium (i.e., 6 times the intracellular AP content of wild-type strain, Ga15, developed in derepressed conditions); AP released into the extracellular fluid corresponded to 34% of total excreted proteins and was equivalent to a purified enzyme preparation.
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    The induction of cytochrome P-450 in the alkane-utilizing yeast Lodderomyces elongisporus: Alterations in the microsomal membrane fraction (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 29-35 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The adaptation of Lodderomyces elongisporus cells to n-alkane utilization was found to be connected with several alterations in the enzyme pattern of the whole cell and the microsomal fraction in particular. A strong induction was found for the microsomal localized cytochrome P-450 alkane hydroxylase system and other enzymes which are directly involved in the terminal degradation pathway of n-alkanes (long-chain alcohol and aldehyde dehydrogenases, catalase). The decrease of the pO2 in the medium enhances the concentration of the constituents of the alkane hydroxylase system as well as that of several other haemoproteins (catalase, cytochrome oxidase), while the long-chain alcohol and aldehyde dehydrogenase enzymes are probably unaffected.
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    An efficient method for the isolation of mycelial protoplasts from Coprinus macrorhizus and other basidiomycetes (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 58-60 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A mixture of commercially available chitinase and cellulase released mycelial protoplasts of Coprinus macrorhizus in yields exceeding 108/ml plasts from C. macrorhizus FisC regenerated hyphae and developed into normal fruiting bodies at frequencies of 20%–50%. The same method also released good yields of protoplasts from several other edible mushroom species.
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    URL: http://dx.doi.org/10.1007/BF00252817
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    The macromolecular composition and essential amino acid profiles of strains of Zymomonas mobilis (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 75-78 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary From continuous culture studies it has been shown that the protein concentrations of strains of Z. mobilis (62–68%) were appreciably higher than for the yeast S.uvarum (45–50%). The DNA and RNA contents were similar for the two species. Comparison of the essential amino acids indicated that Z.mobilis did not exhibit the deficiency in methionine which was apparent in the yeast. Such a study of the macromolecular composition of cells of Z.mobilis is important in assessing its by-product nutritional value for animal feed supplementation.
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    URL: http://dx.doi.org/10.1007/BF00252821
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  • 81
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    Trichococcus flocculiformis gen. nov. sp. nov. A new gram-positive filamentous bacterium isolated from bulking sludge (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 114-119 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A new gram-positive filamentous bacterium with coccoid cells has been isolated from bulking sludge from five sewage treatment plants in West-Germany. The characteristics of five strains are described. Their fatty acids and cell wall composition are similar to the Streptococcaceae and they mainly degrade monomeric and dimeric carbon sources. They are classified as a new genus and species of the family Streptococcaceae: Trichococcus flocculiformis gen. nov. sp. nov.
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    URL: http://dx.doi.org/10.1007/BF00302451
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  • 82
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    Effect of monensin and 2-bromoethanesulfonic acid on fatty acid metabolism and methane production from cattle manure (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 125-130 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of monensin and 2-bromoethanesulfonic acid (BESA) on methane production from cattle manure and on volatile fatty acids metabolism was tested. At 10 days retention time 0.81 biogas per liter cattle manure and day were produced. Methanogenesis was inhibited 20% by 3 mM BESA per liter and 45% by 2–5 mg monensin per liter. When the digestion was inhibited with either of the both drugs, the acetate pool increased drastically. Like in untreated fermentations the propionate pool increased in BESA-inhibited fermentations for several hours after substrate addition. After 24 h however it did not decrease to the low level reached in non-inhibited fermentations. When monensin was the inhibitor, the propionate pool did not change for 15 h, but then decreased with the same rate as in the control experiment. Adaptation processes or detoxification may be responsible for the delayed degradation. The degradation of low concentrations of buty-rate to acetate and the turn over rates of the butyrate pool are almost identical in cattle manure containing BESA, monensin, or no inhibitor. The turn over of 14C-acetate from butyrate degradation is delayed in BESA and monensin inhibited fermentations. From the data presented it can be concluded, that BESA mainly inhibits the methanogens, while monensin seems to inhibit both, methanogenic and nonmethanogenic organisms. However, a fast adaptation to or detoxification of the antibiotic seems to occur.
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    URL: http://dx.doi.org/10.1007/BF00302453
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  • 83
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    Feeding strategy for the production of the new antibiotic myxovirescin A from Myxococcus virescens (Myxobacterales) (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 157-160 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Myxovirescin A is a new antibiotic from Myxococcus virescens. Conditions of growth on peptone media result in the antibiotic being secreted during the transition to the stationary phase. When growth is exponential, no detectable production occurs. In an attempt to improve production of the antibiotic, peptone was fed to the peptone-limited culture at differing feed rates. Product formation was found to be dependent on the peptone supply, and the product concentration could be improved from 0.04 to 2 mg/l myxovirescin A.
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    URL: http://dx.doi.org/10.1007/BF00256447
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  • 84
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    Continuous measurement of ethanol production by aerobic yeast suspensions with an enzyme electrode (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 181-185 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary An alcohol electrode was constructed which consisted of an oxygen probe onto which alcohol oxidase was immobilized. This enzyme electrode was used, in combination with a reference oxygen electrode, to study the short-term kinetics of alcoholic fermentation by aerobic yeast suspensions after pulsing with glucose. The results demonstrate that this device is an excellent tool in obtaining quantitative data on the short-term expression of the Crabtree effect in yeasts. Samples from aerobic glucose-limited chemostat cultures of Saccharomyces cerevisiae not producing ethanol, immediately (within 2 min) exhibited aerobic alcoholic fermentation after being pulsed with excess glucose. With chemostat-grown Candida utilis, however, ethanol production was not detectable even at high sugar concentrations. The Crabtree effect in S. cerevisiae was studied in more detail with commercial baker's yeast. Ethanol formation occurred only at initial glucose concentrations exceeding 150 mg·l-1, and the rate of alcoholic fermentation increased with increasing glucose concentrations up to 1,000 mg·l-1 glucose. Similar experiments with batch cultures of certain ‘non-fermentative’ yeasts revealed that these organisms are capable of alcoholic fermentation. Thus, even under fully aerobic conditions, Hansenula nonfermentans and Candida buffonii produced ethanol after being pulsed with glucose. In C. buffonii ethanol formation was already apparent at very low glucose concentrations (10 mg·l-1) and alcoholic fermentation even proceeded at a higher rate than in S. cerevisiae. With Rhodotorula rubra, however, the rate of ethanol formation was below the detection limit, i.e., less than 0.1 mmol·g cells-1·h-1.
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    URL: http://dx.doi.org/10.1007/BF00256451
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  • 85
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    Butanol from whey ultrafiltrate: batch experiments with Clostridium beyerinckii LMD 27.6 (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 203-206 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary For batch fermentations by Clostridium beyerinckii LMD 27.7 (formerly known as Clostridium butylicum) whey ultrafiltrate, glucose, lactose, and galactose were used as substrates. The aims of the experiments were to find the conditions for butanol production from whey ultrafiltrate and to compare the results with those of other substrates. The conditions necessary for butanol production were established. The mean solvent productivity found on whey ultrafiltrate fermentation was two to three times lower than that found on glucose; the overall solvent yields were comparable. Butanol production from galactose and mixtures of glucose and galactose was also possible.
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    URL: http://dx.doi.org/10.1007/BF00251837
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  • 86
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    An improved synthetic medium for continuous cultivation of Zymomonas mobilis (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 237-240 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A synthetic medium for continuous cultivation of Zymomonas mobilis was developed using the chemostat pulse technique in appropriate experimental designs. Yeast extract could be replaced by a mixture of six mineral salts, Ca-pantothenate, l-as-partate, and l-serine. Kinetic data from continuous cultivations of strains ATCC 10988 and ZM4 are presented and compared with published data.
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    URL: http://dx.doi.org/10.1007/BF00251843
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  • 87
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    Microbial acetate conversion to methane: kinetics, yields and pathways in a two-step digestion process (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 224-228 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Organic waste is converted in a two-stage process to methane and carbon dioxide by mixed cultures of microorganisms. Acetate, a product of acidogenic and acetogenic bacteria and the main substrate for methanogenic bacteria, is an important intermediate of the anaerobic degradation process, which results in the generation of methane. It was shown by labelling experiments using (U-14C) acetate that as much as 65%–96% of the total methane produced came from the acetate. The first order utilization rate for acetate in the methanogenic stages of a two-stage digestion process was between 0.17 h-1 and 0.5 h-1. The kinetics as well as the mass flow and yields of acetate and the methyl group of acetate were determined by pulse-labelling experiments with (U-14C) acetate and (2-14C) acetate without a significant rise of the total concentrations. Up to 58% of the acetate carbon was transformed to methane, and about 30% to carbon dioxide; only 4%–15% was incorporated into the biomass. There are at least two parallel degradation mechanisms in the metabolic transformation of acetate to methane: acetate is cleaved either to form methane and carbon dioxide or to form hydrogen and carbon dioxide, which can be transformed by an additional reaction to methane. Labelling experiments with (2-14C) acetate show that both mechanisms took place at similar order.
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    URL: http://dx.doi.org/10.1007/BF00251840
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  • 88
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    NADH-linked aldose reductase: the key to anaerobic alcoholic fermentation of xylose by yeasts (1984)
    Springer
    Applied microbiology and biotechnology 19 (1984), S. 256-260 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The kinetics and enzymology of d-xylose utilization were studied in aerobic and anaerobic batch cultures of the facultatively fermentative yeasts Candida utilis, Pachysolen tannophilus, and Pichia stipitis. These yeasts did not produce ethanol under aerobic conditions. When shifted to anaerobiosis cultures of C. utilis did not show fermentation of xylose; in Pa. tannophilus a very low rate of ethanol formation was apparent, whereas with Pi. stipitis rapid fermentation of xylose occurred. The different behaviour of these yeasts ist most probably explained by differences in the nature of the initial steps of xylose metabolism: in C. utilis xylose is metabolized via an NADPH-dependent xylose reductase and an NAD+-linked xylitol dehydrogenase. As a consequence, conversion of xylose to ethanol by C. utilis leads to an overproduction of NADH which blocks metabolic activity in the absence of oxygen. In Pa. tannophilus and Pi. stipitis, however, apart from an NADPH-linked xylose reductase also an NADH-linked xylose reductase was present. Apparently xylose metabolism via the NADH-dependent reductase circumvents the imbalance of the NAD+/NADH redox system, thus allowing fermentation of xylose to ethanol under anaerobic conditions. The finding that the rate of xylose fermentation in Pa. tannophilus and Pi. stipitis corresponds with the activity of the NADH-linked xylose reductase activity is in line with this hypothesis. Furthermore, a comparative study with various xylose-assimilating yeasts showed that significant alcoholic fermentation of xylose only occurred in those organisms which possessed NADH-linked aldose reductase.
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    URL: http://dx.doi.org/10.1007/BF00251847
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  • 89
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    The behaviour of yeast flocs in hindered settling and fluidized bed regimes (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 10-15 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Sedimentation and fluidization of yeast flocs were found to be non-synonymous processes. The analysis of Richardson and Zaki (1954) was found not to hold when applied to yeast flocs in both regimes. Partial support and channelling were implicated in the deviations from idela behaviour. Other factors responsible for the behaviour of yeast flocs in these regimes are discussed.
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    URL: http://dx.doi.org/10.1007/BF00254639
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  • 90
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    Use of alfalfa residual juice as a substrate for propagation of the red yeast Phaffia rhodozyma (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), 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: Summary Alfalfa residual juice (ARJ) supported good growth of the yeast Phaffia rhodozyma but formation of astaxanthin was inhibited. Supplementary nutrients did not reverse the inhibition, indicating that the the juice probably contained some inhibitor of astaxanthin biosynthesis. Six strains of P. rhodozyma were tested and found to be susceptible to the inhibitory effects of the juice. Concentrations of ARJ above 1.25% (v/v) were inhibitory to pigmentation of the yeast. Above approximately 3.7%, total inhibition of astaxanthin formation was observed but some chromogenic components of the juice were adsorbed on Phaffia cells and appeared as artefacts in astaxanthin analyses. Phaffia biomass produced in ARJ showed greater susceptibility to autolysis than that produced in a peptone-glucose-salts medium. Supplementation of ARJ with glucose enhanced yield of cell mass and minimised the autolytic phenomenon, and is potentially useful for producing Phaffia biomass for use as a source of single cell protein. Unsupplemented brewer's malt wort and molasses, separately and in a suitable combination, were compared with ARJ and were found suitable for growth and pigmentation of P. rhodozyma.
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    URL: http://dx.doi.org/10.1007/BF00254643
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  • 91
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    Uptake and activation of acetate and butyrate in Clostridium acetobutylicum (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 66-71 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The pathway for uptake of acids during the solvent formation phase of an acetone-butanol fermentation by Clostridium acetobutylicum ATCC 824 was studied. 13C NMR investigations on actively metabolizing cells showed that butyrate can be taken up from the medium and quantitatively converted to butanol without accumulation of intermediates. The activities of acetate phosphotransacetylase, acetate kinase and phosphate butyryltransferase rapidly decreased to very low levels when the organism began to form solvents. This indicates that the uptake of acids does not occur via a reversal of these acid forming enzymes. No short-chain acyl-CoA synthetase activity or butyryl phosphate reducing activity could be detected. Based on our results and a critical analysis of literature data on acetone-butanol fermentations, it is suggested that an acetoacetyl-CoA: acetate (butyrate) CoA-transferase is solely responsible for uptake and activation of acetate and butyrate in C. acetobutylicum. The transferase exhibits a broad carboxylic acid specificity. The key enzyme in the uptake is acetoacetate decarboxylase, which is induced late in the fermentation and pulls the transferase reaction towards formation of acetoacetate. The major implication is that it is not feasible to obtain a batch-wise butanol fermentation without acetone formation and retention of a good yield of butanol.
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    URL: http://dx.doi.org/10.1007/BF00254648
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  • 92
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    Modelling of the enzymatic hydrolysis of cellobiose and cellulose by a complex enzyme mixture of Trichoderma reesei QM 9414 (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 176-182 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The enzymatic hydrolysis of cellobiose and cellulose by the cell-free culture filtrate of Trichoderma reesei QM 9414 was investigated. The concentrations of cellobiose and glucose were measured as a function of time for different initial concentrations of cellobiose. It was not possible to describe these concentration variations by a model which considers only the cellobiase hydrolysis with competitive and noncompetitive substrate and product inhibition; it is necessary that the endo-β-1.4-glucanase with competitive product inhibition is also taken into account. The enzymatic hydrolysis of cellulose (Avicel) was described with a mathematical model by using the results of the decomposition of cellobiose by the same enzyme mixture. the identified model parameters are presented. A sensitivity analysis of the parameter was carried out also.
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    URL: http://dx.doi.org/10.1007/BF00253727
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  • 93
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    The laminarinase system of Streptomyces sp., ATCC 11238 (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 207-212 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Extracellular proteins from Streptomyces sp. ATCC 11238 grown on fungal mycelia and chitin as C- and N-sources were concentrated by ultrafiltration and acetone precipitation. The crude preparation containing chitin and laminarin degrading enzymes was fractionated by repeated gel filtrations. Three different types of β-1,3-glucanases were found. Besides oligomeric breakdown products laminaritriose is the main product of laminarin hydrolysis by one endo-β-1,3-glucanase. A second laminarin degrading (exo-splitting) enzyme yields predominantly laminaribiose. Another exo-β-1,3-glucanase liberates glucose but no, oligosaccharides from the nonreducing end of laminarin.
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    URL: http://dx.doi.org/10.1007/BF00253732
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  • 94
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    Effect of phenoxyalkanoic acid herbicides on the fermentative production of l-lysine (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 129-132 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of the herbicides MCPA, MCPB, mecoprop, dichlorprop, 2,4-D, 2,4-DB, and 2,4,5-T on l-lysine fermentation was investigated using a lysine-producing mutant of Corynebacterium glutamicum. Stimulation of l-lysine production by 6% to 36% was observed in shaken flask experiments when the test herbicides were added at a concentration of 5 · 10-4 M to growing cultures after 24 h of cultivation. The most effective stimulators were MCPA, mecoprop and dichlorprop. Detailed studies of the effect of MCPA (5 · 10-6 M to 5 · 10-3 M) showed that the degree of stimulation depended on medium composition and aeration. In the synthetic medium, maximum production of 50 g · l-1 lys · HCl occurred at 5 · 10-4 M MCPA and an oxygen transfer rate (OTR) of 1.97 g O2 · l-1 · h-1, while 61.7 g · l-1 of lys · HCL was formed at 5 · 10-3 M MCPA and an OTR of 3.75 g O2 · l-1 · h-1. In the amino-nitrogen rich medium, maximum production of 42 g · l-1 lys · HCl was observed at 5 · 10-6 M MCPA and an oxygen transfer rate of 1.5 g O2 · l-1 · h-1. Results from batch l-lysine fermentation in a fermenter showed similar stimulatory effects, with an optimal concentration of MCPA for l-lysine production of 5 · 10-5 M. Without herbicide addition, the test strain produced 16.25 g · l-1 of product and with addition of 5 · 10-5 M MCPA, the same strain produced 52.1 g · l-1 lys · HCl after 72 h of fermentation.
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    URL: http://dx.doi.org/10.1007/BF00252590
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    Immobilization of yeast cells in hydroxyethylmethacrylate gels (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 233-237 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Whole cells of Saccharomyces cerevisiae were entrapped in polymers of 2-hydroxyethylmetha-crylate and sucrose hydrolysis catalysed by its invertase was investigated. Analysis of the experimental results confirmed that diffusional resistance to mass transfer of reactant and product was not induced by immobilization. For the yeast cells in the hydrogel, invertase activity obeyed a Michaelis-Menten kinetic and the value of Km (40 mM) was the same as that for yeast cells in bulk phase. The recovery of biocatalyst activity ranged between 17% and 23%, depending on immobilization temperature; the optimum pH range was found to be slightly wider. Storage stability at refrigerator temperature was quite satisfactory; invertase half-life was 267 days. Operational stability of immobilized cells at 45°C (half-life 110 days) was almost twice that of free cells. Finally, cell distribution in the polymer, observed with a scanning electron microscope, was found to be uniform.
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    Constitutive expression of the human fibroblast interferon gene is elicited in cultured mouse L cells by the long terminal repeat of Moloney sarcoma virus (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), 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: Summary We have used a chimerical plasmid containing the long terminal repeat of Moloney sarcoma virus to direct the expression of the human fibroblast interferon gene in mouse L cells. Constitutive secretion in cell culture supernatants was achieved at a level higher than 2.103 U/ml/72 h. The antiviral activity was indistinguishable from that of authentic human fibroblast interfereon by both immunological and physical criteria. Northern blotting analysis showed unambiguously that the expression was under the control of the putative transcriptional regulatory sequences previously described in the long terminal repeat of Moloney murine sarcoma virus (Dhar et al. 1980).
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    URL: http://dx.doi.org/10.1007/BF00253729
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    Development of an optimal heterotrophic growth medium for Chlorella vulgaris (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 281-283 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Final biomass yields of Chlorella vulgaris cultured heterotrophically in bristol medium amended with 0.1% (w/v) yeast extract (Difco) or 0.5% glucose (w/v) were 26 and 58 times higher, respectively, than yields obtained for autotrophically grown cells in the light. Similarly, final biomass increases were 35 and 138 fold for these organic substrates in the dark. The mixture of 0.1% yeast extract and 0.5% glucose was optimal and produced increases in final biomass of 70 and 140 times in the light and dark, respectively.
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    URL: http://dx.doi.org/10.1007/BF00250641
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  • 98
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    Flow dynamics of immobilized enzyme reactors (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 303-309 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Enzymic conversion of glucose to fructose was carried out in a packed bed and in a fluidized bed reactor. The flow dynamics of these two flow systems, loaded with two different types of immobilized loaded with two different types of immobilized glucose isomerase particles, were studied. The theoretical RTD curve calculated from the axial dispersed plug flow model equation was matched to the experimental RTD curve by an optimization technique. The effect of fluid velocity on the extent of liquid dispersion was established. Theoretical predictions on the conversion of glucose to fructose were calculated using three mathematical models, namely, a plug flow model, a continuous stirred tank reactor (CSTR) model and an axial dispersed plug flow model. The experimental results showed that the axial dispersed plug flow model was superior in predicting the performance of both the packed bed and fluidized bed reactor.
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    URL: http://dx.doi.org/10.1007/BF00270590
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  • 99
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    Dissociation of cephamycin and clavulanic acid biosynthesis in Streptomyces clavuligerus (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 318-325 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Streptomyces clavuligerus produced simultaneously cephamycin C and clavulanic acid in defined medium in long-term fermentations and in resting-cell cultures. Biosynthesis of cephamycin by phosphate-limited resting cells was dissociated from clavulanic acid formation by removing either glycerol or sulphate from the culture medium. In absence of glycerol no clavulanic acid was formed but cephamycin production occurred, whereas in absence of sulphate no cephamycin was synthesized but clavulanic biosynthesis took place. Sulphate, sulphite and thiosulphate were excellent sulphur sources for cephamycin biosynthesis while l-methionine and l-cysteine were poor precursors of this antibiotic. Increasing concentrations of sulphate also stimulated clavulanic acid formation. The biosynthesis of clavulanic acid was much more sensitive to phosphate (10–100 mM) regulation than that of cephamycin. Therefore, the formation of both metabolites was pertially dissociated at 25 mM phosphate. By contrast, nitrogen regulation by ammonium salts or glutamic acid strongly reduced the biosynthesis of both cephamycin and clavulanic acid.
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  • 100
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    Mutants of Myxococcus xanthus impaired in protein secretion: an approach to study of a secretory mechanism (1984)
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 344-350 
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    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Bacteria able to secrete proteins efficiently into the growth medium occur relatively rarely amongst Gram-negative species. However, the increasing technological interest in protein secretion has focused attention on this process. We have demonstrated that Myxococcus xanthus actively secretes protein. The number of proteins secreted is quite large, but the total amount is strictly regulated and remains constant under conditions that change the specific activities of some of the secreted enzymes. Tn5-insertion mutants were obtained which were impaired in what seems to be the control system for protein secretion. Two of the mutants displayed increased levels of extracellular protein.
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    URL: http://dx.doi.org/10.1007/BF00270598
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