bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of fatty acid esters by a recombinant cutinase in reversed micelles
Authors: Sebastião M. J. , Cabral J. M. S. , Aires‐Barros M. R. 
Published: December 2004

AbstractFusarium solani pisi recombinant cutinase, solubilized in AOT/isooctane‐reversed micelles, was used to catalyze the esterification of fatty acids with aliphatic alcohols. Some relevant parameters for the enzyme activity such as pH, Wo (water/surfactant molar ratio), temperature, and substrate concentration were optimized. Maximal specific activity was obtained for hexanol. The cutinase showed selectivity for short‐chain fatty acids. The stability of the microencapsulated cutinase was investigated at various concentrations of water and different values of pH. Oleic acid had a negative effect on the cutinase stability, while hexanol proved to be a strong stabilizer increasing the half‐life of the enzyme about 45 times. © 1993 John Wiley & Sons, Inc.
Charged fusions for selective recovery of β‐galactosidase from cell extract using hollow fiber ion‐exchange membrane adsorption
Authors: Heng Meng H. , Glatz Charles E. 
Published: December 2004

AbstractWe explored the use of charged fusions for selective recovery of β‐galactosidase from cell extract using a low‐cost, easily scaled, fast, charge‐based separation technique—ion exchange on hollow fiber ion‐exchange membranes (HFIEMs). The additional charges carried by a series of anionic fusion tails allowed selective binding and release of β‐galactosidase from Escherichia coli cell extract using the HFIEM cartridge. The purification factors increased with fusion length. The β‐galactosidase was recovered in active form. For the longest fusion studied, more than sixfold enrichment in specific activity was attained. The specific activity of the recovered fraction is comparable with that of commercial wild‐type β‐galactosidase and affinity‐purified fusion protein. © 1993 John Wiley & Sons, Inc.
The molecular weight cut‐off of microcapsules is determined by the reaction between alginate and polylysine
Authors: Vandenbossche Geert M. R. , Van Oostveldt Patric , Demeester Joseph , Remon Jean‐Paul 
Published: December 2004

AbstractMammalian cells encapsulated in alginate‐polylysine microcapsules are used as artificial organs in cancer research and in biotechnology. These applications require microcapsules with a reproducible mol. wt. cut‐off. The high cost of the polycation, polylysine, requires an efficient preparation procedure. This article shows that the overall reported contact time of 5 minutes at ambient conditions should be increased several times in order to reach a maximal binding between the calcium alginate beads and 0.1% (w/v) polylysine solutions. An increase of the polylysine concentration from 0.0125% to 0.8% (w/v) resulted in a faster maximal binding, but the amount of polylysine bound increased also. Immersion of calcium alginate beads with a diameter of 750 μm, prepared from 1 mL alginate, in 30 mL of a 0.8% (w/v) polylysine solution, resulted in a polylysine spill of more than 89%. The time required to reach a maximal binding was related to the reaction temperature. The interaction zone between calcium alginate beads and fluorescein isothiocyanate‐labeled polylysine solutions was visualized with a confocal laser scanning microscope as a function of time. Microcapsules, prepared at 40°C with 0.1% (w/v) polylysine solutions with mol. wts. between 12 and 249.2 kD, were permeable for fluorescein isothiocyanate‐labeled dextran, mol. wt. 4.7, but not for 40.5 kD. Higher polylysine concentrations resulted in a membrane with a mol. wt. cut‐off lower than 4.7 kD. © 1993 John Wiley & Sons, Inc.
Immobilization of enzyme onto cellulose–titanium oxide composite fiber
Authors: Kurokawa Y. , Sano T. , Ohta H. , Nakagawa Y. 
Published: December 2004

AbstractFibers of a cellulose–TiO2 composite were prepared by the reaction of cellulose with titanium iso‐propoxide. Enzymes were immobilized on the fibers easily and simply under mild conditions. The fibers were stable in common solvents, high ionic solutions, and over a wide range of pH values 3–10. © 1993 John Wiley & Sons, Inc.
Generation of a pH gradient in an immobilized enzyme system
Authors: Byers James P. , Shah Manish B. , Fournier Ronald L. , Varanasi Sasidhar 
Published: December 2004

AbstractSeveral examples of two‐step sequential reactions exist where, because of the poor equilibrium conversion by the first reaction, it is desirable to conduct the two reactions simultaneously. In such a scheme, the product of the first reaction is continuously removed by the second reaction, thus not allowing the first reaction to approach chemical equilibrium. Therefore, the first reaction is allowed to proceed in the desired direction at an appreciable rate. However, in many biochemical applications where enzyme catalysts are involved, the enzyme's activities are strong functions of pH. Where the pH optima of the first and second reaction differ by three to four units, the above reaction scheme would be difficult to implement. In these cases, the two reactions can be separated by a thin permeable membrane across which the desired pH gradient is maintained. In this article, it was shown, both by theory and experiment, that a thin, flat membrane of immobilized urease can accomplish this goal when one face of the membrane is exposed to the acidic bulk solution (pHb = 4.5) containing a small quantity of urea (0.01 M). In this particular case, the ammonia that was produced in the membrane consumed the incoming hydrogen ions and thus maintained the desired pH gradient. Experimental results indicate that with sufficient urease loading, the face of the membrane opposite to the bulk solution could be maintained at a pH that would allow many enzymes to realize their maximum activities (≈ 7.5). It was also found that this pH gradient could be maintained even in the presence of a buffer, which greatly enhances the transport of protons into the membrane. © 1993 John Wiley & Sons, Inc.
Detection of bacterial contamination in cultures of eucaryotic cells by gas chromatography–mass spectrometry
Authors: Elmroth Ingrid , Fox Alvin , Holst Olle , Larsson Lennart 
Published: December 2004

AbstractThe use of gas chromatography–mass spectrometry for early detection of bacterial contaminations in cultures of baker's yeast, Penicillium chrysogenum, and an animal cell line was evaluated; muramic acid and characteristic cellular fatty acids were used as analytes. By analyzing branched‐chain and cyclopropane‐substituted fatty acids as methyl esters, Staphylococcus epidermidis, Bacillus subtilis, Lactobacillus reuteri, Enterobacter cloacae, and Pseudomonas fluorescens were detected in a 500‐fold excess (w/w) of baker's yeast; the amounts injected corresponded to 300 ng (dry mass) of the bacteria. Contamination with Bacillus was detected in cultures of Penicillium chrysogenum and animal cells by analyzing muramic acid, both as its alditol acetate derivative, using electron impact ionization, and its trifluoroacetyl methyl glycoside derivative, using negative ion‐chemical ionization. The trifluoroacetylated derivative was detected in injected amounts corresponding to 1 × 103 bacterial cells in the contaminated animal cell line, whereas amounts corresponding to 1 × 105 bacteria were required for detection of the alditol acetate derivative; the amounts in the original samples were 5 × 105 and 5 × 106, respectively. However, the alditol acetate method exhibited lower chemical interferences than the trifluoroacetyl methyl glycoside procedure. The results show the potential of using gas chromatographic–mass spectrometric analysis of cellular constituents for the detection of bacterial contaminations in eucaryotic cultures as an alternative to conventional microbiological methods. © 1993 John Wiley & Sons, Inc.
Microbial utilization of levoglucosan in wood pyrolysate as a carbon and energy source
Authors: Prosen Elizabeth M. , Radlein Desmond , Piskorz Jan , Scott Donald S. , Legge Raymond L. 
Published: December 2004

AbstractThe Waterloo Fast Pyrolysis Process (WFPP) can produce an organic liquid high in levoglucosan (1, 6‐anhydro‐β‐D‐glucopyranose) content from suitably pretreated lignocellulosics. A variety of fungi and yeasts were screened for their ability to utilize and ferment this organic liquid. To enhance its fermentability, the pyrolysis tar was posttreated in three different ways: (1) an aqueous extract (lignin removed); (2) activated charcoal treated (lignin and aromatics removed); and (3) acid hydrolysate (lignin and aromatics removed with the levoglucosan hydrolyzed to glucose). Four fungal strains were examined. None grew in the aqueous extract, but all grew equally well in both the activated charcoal treated and the acid hydrolysate, suggesting that the aromatic species were inhibitory to growth. Seven yeast species were examined, two of which did not grow on any of the extracts. Five of the yeast strains grew well on both the aqueous extract as well as the activated charcoal extract. The hydrolysate was optimal in terms of biomass yield and ethanol production. Ethanol yields on the hydrolysate were comparable or better than those on glucose. Ethanol was also produced in the aqueous extract and activated charcoal‐treated substrate, but yields were considerably lower than on the hydrolysate or glucose. It is apparent that a wood pyrolysate maximized for levoglucosan can serve as a fermentable substrate, although postpyrolysis clean‐up appears necessary. © 1993 John Wiley & Sons, Inc.
A fractal model for the characterization of mycelial morphology
Authors: Patankar Dhananjay B. , Liu Tuan‐Chi , Oolman Timothy 
Published: December 2004

AbstractA new technique based on a fractal model has been developed for the quantification of the macroscopic morophology of mycelia. The morphological structuring is treated as a fractal object, and the fractal dimension, determined by an ultrasonic scattering procedure developed for the purpose, serves as a quantitative morphological index. Experimental observations reported earlier and simulations of mycelial growth, carried out using a probabilistic‐geometric growth model developed for the purpose, both validate the applicability of the fractal model. In experiments with three different species, the fractal dimensions of pelletous structures were found to be in the range 1.45–2.0 and those of filamentous structures were in the range 1.9–2.7, with values around 2.0 representing mixed morphologies. Fractal dimensions calculated from simulated mycelia are in rough agreement with these ranges. The fractal dimension is also found to be relatively insensitive to the biomass concentration, as seen by dilution of the original broths. The relation between morphology and filtration properties of the broths has also been studied. The fractal dimension shows a strong correlation with the index of cake compressibility and with the Kozeny constant, two filtration parameters that are known to be morphology dependent. This technique could thus be used to develop correlations between the morphology, represented by the fractal dimension, and important morphology‐dependent process variables. © 1993 John Wiley & Sons, Inc.
Partitioning behavior and enrichment of proteins with reversed micellar extraction: I. Forward extraction of proteins from aqueous to reversed micellar phase
Authors: Nishiki Tadaaki , Sato Ikuto , Kataoka Takeshi , Kato Daisaburo 
Published: December 2004

AbstractProtein extractions using aerosol OT (AOT)–isooctane reverse micelle solutions have been studied to explore the potential for separating and enriching proteins with the reversed micellar extraction. The effects of pH, ionic strength, and different cations of chlorides in a bulk aqueous phase and of AOT concentration in an organic phase on the partitioning of lysozyme and myoglobin and the solubilization of water are presented in detail. The extraction of lysozyme was affected by the concentration of potassium or barium but was almost independent of that of sodium or calcium, whose ionic diameter is smaller than that of potassium and barium. For the extraction of myoglobin, however, the effect of barium concentration was not appreciable. Lysozyme could be enriched into the reversed micellar phase up to 30 times the aqueous feed concentration. © 1993 John Wiley & Sons, Inc.
Effect of surfactants on cellulose hydrolysis
Authors: Helle Steve S. , Duff Sheldon J. B. , Cooper David G. 
Published: December 2004

AbstractThe effect of surfactants on the heterogeneous enzymatic hydrolysis of Sigmacell 100 cellulose and of steam‐exploded wood was studied. Certain biosurfactants (sophorolipid, rhamnolipid, bacitracin) and Tween 80 increased the rate of hydrolysis of Sigmacell 100, as measured by the amount of reducing sugar produced, by as much as seven times. The hydrolysis of steam‐exploded wood was increased by 67% in the presence of sophorolipid. At the same time, sophorolipid was found to decrease the amount of enzyme adsorbed onto the cellulose at equilibrium. Sophorolipid had the greatest effect on cellulose hydrolysis when it was present from the beginning of the experiment and when the enzyme/cellulose ratio was low. © 1993 John Wiley & Sons, Inc.
Optimization of alkyl β‐D‐galactopyranoside synthesis from lactose using commercially available β‐galactosidases
Authors: Stevenson David E. , Stanley Roger A. , Furneaux Richard H. 
Published: December 2004

AbstractCommercially available lactase (β‐D‐galactoside galactohydrolase, EC 3.2.1.23) enzymes produced from Kluyveromyces fragilis and Kluyveromyces lactis were accessed as catalysts for use in the production of β‐galactopyranosides of various alcohols using lactose as galactosyl donor. The yield of galactoside was enhanced by using the highest practical concentrations of both lactose and alcohol acceptor. The concentrations and thus yield, were limited by the solubility of the substrates. The increase in galactoside yield with increasing lactose concentration appeared to be specific to the lactose substrate and not due to water activity alterations, because addition of maltose to a fixed concentration of lactose had no effect. During the course of the reaction, the yield of galactoside peaked after around 70% to 80% of the lactose was consumed, due to hydrolysis of the product by the enzyme. A wide variety of compounds with primary or secondary hydroxyl groups could act as acceptors, the essential requirement being at least some water solubility. Addition of organic cosolvents had little effect on galactoside yield except when it increased the water solubility of sparingly soluble alcohols. Some galactosides were synthesized on a gram scale to determine practical product recoveries and improve purification methods for large‐scale synthesis. Initial purification by hydrophobic chromatography (for galactosides of hydrophobic alcohols) or strong anion‐exchange chromatography (for galactosides of hydrophilic alcohols) separated galactosides, galactobiosides, and higher oligomers from reducing sugars. A facile separation of the galactoside and galactobioside could then be effected by flash chromatography on silica gel. © 1993 John Wiley & Sons, Inc.
Toxicity of homologous series of organic solvents for the gram‐positive bacteria Arthrobacter and Nocardia Sp. and the gram‐negative bacteria Acinetobacter and Pseudomonas Sp.
Authors: Vermuë Marian , Sikkema Jan , Verheul Annette , Bakker Rudolf , Tramper Johannes 
Published: December 2004

AbstractThe toxicity of homologous series of organic solvents has been investigated for the gram‐positive bacteria, Arthrobacter sp. and Nocardia sp., and the gram‐negative bacteria, Acinetobacter sp. and Pseudomonas sp. The hydrophobicity of the solvent, expressed by its logPoctanol, proves to be a good measure for the toxicity of solvents in a two‐phase system. The transition from toxic to nontoxic solvents occurs between logPoctanol 3 and 5 and depends on the homologous series. No correlation has been found between the hydrophobicity of the substituent on the alkyl backbone of the solvent and the location of the transition point in toxicity. The logPoctanol, above which all solvents are nontoxic, is used to express the solvent tolerance of the bacteria. In general, the solvent tolerance of gram‐negative bacteria is found to be slightly higher than that of gram‐positive bacteria, but this does not hold for all homologous series of organic solvents investigated.Because the toxicity effects of organic solvents in a two‐phase system can be ascribed to molecular as well as phase toxicity effects, molecular toxicity effects were investigated separately in a one‐phase system with subsaturating amounts of organic solvent. The solvent concentration in the aqueous phase, at which 50% of the metabolic activity of the bacteria is lost, is used to express solvent toxicity. This concentration is found to be similar for the gram‐positive Arthrobacter and the gram‐negative Acinetobacter. Assuming the critical membrane concentration theory (G. J. Osborne et al. Enzyme Microb. Technol. 1990, 12: 281–291) to be valid, it can be concluded that differences in solvent tolerance between these two bacteria, cannot be ascribed to differences in response to molecular toxicity. Prediction of the toxicity of any solvent, using the critical membrane theory, appears to be possible in the case of alkanols or alkyl acetates. However, prediction of the toxicity of ethers appears to be impossible. © 1993 John Wiley & Sons, Inc.
Morphological measurements on Penicillium chrysogenum broths by rheology and filtration methods
Authors: Liu Tuanchi , Yu Duncan 
Published: December 2004

AbstractThe morphology parameters of mycelial culture (Penicillium chrysogenum) were measured and quantified by rheology and filtration methods. Two of the morphology parameters obtained from rheology measurements, δ defined by the Casson equation and δ* defined by intrinsic viscosity, were found to vary systematically with broth age and with the observed morphology by microscopy. Three of the filtration parameters, hyphal density, Kozeny constant, and index of compressibility, are demonstrated as sensitive indicators of the broth age and mycelial morphology. Two of the morphology parameters, δ and δ*, were used to cross‐correlate with hyphal density. Because various mycelial fermentations require different growth morphologies (pellet and filament) for optimum product yield and the morphology of mycelial broths varies with broth age, it is suggested that these morphology parameters could be used to represent the morphology of mycelial broths quantitatively. © 1993 John Wiley & Sons, Inc.
Efficiency of fatty acid synthesis by oleaginous yeasts: Prediction of yield and fatty acid cell content from consumed C/N ratio by a simple method
Authors: Granger L‐M. , Perlot P. , Goma G. , Pareilleux A. 
Published: December 2004

AbstractIn nitrogen‐limited media, growth and fatty acid formation by the oleaginous yeast Rhodotorula glutinis, i.e., yield and fatty acid cell content, have been characterized regarding carbon and nitrogen availabilities. It was shown that the formation of fatty acid free biomass was limited by nitrogen availability, whereas the fatty acid production was directly dependent on the consumed C/N ratio. According to these observations, the fraction of substrate consumed for fatty acid synthesis was estimated by using a simple method based on the actual yields, i.e., the mass of carbon source strictly converted into fatty acids and fatty acid free biomass. From these results, relationships were established allowing to predict in a simple and performing manner the maximal attainable fatty acid cell content and yield from the available carbon and nitrogen. These relationships were validated by using experimental data obtained by various authors with different yeast strains, and the proposed method was compared to the energetic and mass balance method previously described. © 1993 John Wiley & Sons, Inc.
Affinity–based reversed micellar protein extraction: I. Principles and protein–ligand systems
Authors: Kelley Brian D. , Wang Daniel I. C. , Hatton T. Alan 
Published: December 2004

AbstractAffinity cosurfactants, consisting of hydrophilic ligands derivatized with hydrophobic tails, increase the efficiency of selective protein recoveries using reversed micelles by extending the operating range of pH and salt concentration over which an extraction can be performed. Three different affinity cosurfactant–protein pairs have been used to demonstrate the principles of this extractive technique: (i) concanavalin A, a lectin, was extracted with the addition of octyl glucoside; (ii) natural amphiphiles, such as lecithin, were used to extract myelin basic protein, a membrane‐associated protein known to recognize and bind the phosphatidylcholine headgroup; and (iii) alkyl boronic acids were used to extract chymotrypsin. The enhancement in protein transfer correlated with the binding strength of the free ligand and protein in aqueous solution. Several control studies confirmed the biospecificity of the interactions of protein and affinity cosurfactant. © 1993 John Wiley & Sons, Inc.
Morphological characterization of yeast by image analysis
Authors: Pons M. N. , Vivier H. , Rémy J. F. , Dodds J. A. 
Published: December 2004

AbstractA semiautomatic image analysis method, with minimal operator intervention, has been developed to characterize the morphology of yeast cells under the assumption that they have an ellipsoidic shape. The cells are observed by optical microscopy and the surface and the minor and major half‐axes of the projection of the ellipsoid on the image plane are determined. Using this method, yeast size distributions and population kinetics (single and budding cells, cell clusters) are determined during alcoholic fermentations. Combination of image analysis with a methylene blue viability test is examined but the staining procedure induces a change in the size of the cells. © 1993 John Wiley & Sons, Inc.
Effect of solution environment on the permeability of red blood cells
Authors: Langsdorf Leah J. , Zydney Andrew L. 
Published: December 2004

AbstractThe cell membrane permeability governs the rate of solute transport into and out of the cell, significantly affecting the cell's metabolic processes, viability, and potential usefulness in both biotechnological applications and physiological systems. Most previous studies of the cell membrane permeability have neglected the possible effects of suspending medium on membrane transport, even though there is extensive experimental evidence that suspending phase composition can significantly affect other properties related to the cell membrane (e.g., cell deformability, fragility, and aggregation rate). This study examined the effects of suspending phase composition (both proteins and electrolytes) on the permeability of human red blood cells to the metabolites creatinine and uric acid. Data were obtained using a stirred ultrafiltration device with direct cell‐ and proteinfree sampling through a semipermeable membrane. Both the uric acid and creatinine permeabilities were strongly affected by the suspending phase composition, with the permeabilities in different buffer solutions varying by as much as a factor of three. The predominant factors affecting the permeability were the presence (or absence) of chloride, phosphate/adenine, and proteins, although the magnitude and even the direction of these effects were significantly different for creatinine and uric acid transport. The dramatic differences in behavior for uric acid and creatinine reflect the different transport mechanisms for these solutes, with uric acid transported by a carrier‐mediated mechanism and creatinine transported by passive diffusion through the lipid bilayer. These results provide important insights into the effects of solution environment on cell membrane transport and other cell membrane‐mediated properties. © 1994 John Wiley & Sons, Inc.