bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered physicochemical characteristics of polyethylene glycol linked beet stem oxalate oxidase
Authors: Varalakshmi P. , Lathika K. M. , Raghavan K. G. , Singh B. B. 
Published: December 2004

AbstractOxalate oxidase (EC 1.2.3.4), obtained from the beet stem, was covalently linked to polyethylene glycol (PEG). Compared with native enzyme, the modified oxalate oxidase exhibited decreased electrophoretic mobility, increased storage stability, higher thermal stability, and resistance to heavy metal inactivation and proteolytic digestion. The chemical modification of oxalate oxidase with PEG also brought about a marked shift in its optimal pH, from pH 4.5 to 6.5, without altering its Michaelis constant (Km) significantly. These acquired properties of the immobilized oxalate oxidase render it suitable for possible applications in clinical, nutritional, and medical fields. © 1995 John Wiley & Sons, Inc.
A reagentless amperometric electrode based on carbon paste, chemically modified with D‐lactate dehydrogenase, NAD+, and mediator containing polymer for D‐lactic acid analysis. II. On‐line monitoring of fermentation process
Authors: Shu Hun‐Chi , Gorton Lo , Persson Björn , Mattiasson Bo 
Published: December 2004

AbstractThe production of D‐lactic acid by Lactobacillus delbrueckii (ATCC 9649) during fermentation was monitored on‐line with a reagentless D‐lactate dehydrogenase modified carbon paste electrode in a flow injection system integrated with a filtration sampling device. The time delay between sampling and detection was approximately 6 min. The use of an electropolymerized ortho‐phenylenediamine membrane on the elctrode resulted in a very selective sensor response with acceptable stability and sensitivity. The D‐lactate concentrations determined on‐line agreed well with those determined by a standard method, suggesting that this sensor system is suitable for on‐line monitoring of fermentation processes. © 1995 John Wiley & Sons, Inc.
Citric acid production by Candida lipolytica Y 1095 in cell recycle and fed‐batch fermentors
Authors: Rane Kishore D. , Sims Kevin A. 
Published: December 2004

AbstractThe effect of dissolved oxygen on citric acid production and oxygen uptake by Candida lipolytica Y 1095 was evaluated in cell recycle and fed‐batch fermentation systems. The maximum observed volumetric productivity, which occurred at a dilution rate of 0.06 h−1, a dissolved oxygen concentration of 80%, and a biomass concentration of 5% w/v, in the cell recycle system, was 1.32 g citric acid/L · h. At these same conditions, the citric acid yield was 0.65 g/g and the specific citric acid productivity was 24.9 mg citric acid/g cell · h. In the cell recycle system, citric acid yields ranged from 0.45 to 0.72 g/g. Both the volumetric and specific citric acid productivities were dependent on the dilution rate and the concentration of dissolved oxygen in the fermentor. Similar productivities (1.29 g citric acid/L · h) were obtained in the fed‐batch system operated at a cycle time of 36 h, a dissolved oxygen concentration of 80%, and 60 g total biomass. Citric acid yields in the fed‐batch fermentor were consistently lower than those obtained in the cell recycle system and ranged from 0.40 to 0.59 g/g. Although citric acid yields in the fed‐batch fermentor were lower than those obtained in the cell recycle system, higher citric:isocitric acid ratios were obtained in the fed‐batch fermentor. As in the cell recycle system, both the volumetric and specific citric acid productivities in the fed‐batch fermentor were dependent on the cycle time and dissolved oxygen concentration. © 1995 John Wiley & Sons, Inc.
Effect of the concentration of DODMAC and 1‐decanol on the behavior of reverse micelles in the extraction of amino acids
Authors: Wang W. , Weber M. E. , Vera J. H. 
Published: December 2004

AbstractThe concentrations of dioctyldimethyl ammonium chloride (DODMAC) and 1‐decanol in isooctane needed to form reverse micelles by phase contact have been determined. The behavior of these reverse micelles in the extraction of aspartic acid, glutamic acid, and threonine was studied by analyzing all of the ionic species in the aqueous phase. The amino acid is extracted from the aqueous phase by exchanging with the Cl− counterions of DODMAC in the reverse micelles. The ionic species in the reverse micelles tend toward their undissociated states as the water uptake by the reverse micelles decreases. The effect of 1‐decanol on the extraction of the amino acids with two negative charges is due to the change in the water uptake of the reverse micelles. The concentration of DODMAC has no effect on the ion exchange of the amino acid with one negative charge with the Cl− counterions of DODMAC in the reverse micelles. Higher molar ratios of decanol to DODMAC favor the selective separation of amino acids with different charge numbers. © 1995 John Wiley & Sons, Inc.
Monitoring of Saccharomyces cerevisiae in commercial bakers' yeast fermentation
Authors: Hatch Randolph T. , Veilleux Brendan G. 
Published: December 2004

AbstractIn the highly competitive market of commercial bakers' yeast, fermentations are operated for maximum efficiency and minimum production cost. In order to maintain competitiveness, the fermentations must be highly consistent with minimum variation in yeast performance, maximum yield on raw materials, and minimum production of undesirable side products. The use of advanced instrumentation is of critical importance to achieving these goals by the production engineer. An in situ optical density probe was used to determine the yeast cell density in full‐scale commercial bakers' yeast fermentations. The optical density probe results were compared with oxygen uptake rate analyses, packed cell volume, and off‐line measured cell dry weights. The most accurate measurement of cell density was found to be the optical density probe. This instrument allowed the on‐line determination of cell density with highly consistent results from fermentation batch to batch and with out the need for intermittent recalibration. © 1995 John Wiley & Sons, Inc.
Simultaneous production of H2 and O2 in closed vessels by marine Cyanobacterium anabaena sp. TU37‐1 under high‐cell‐density conditions
Authors: Kumazawa Shuzo , Asakawa Hidenori 
Published: December 2004

AbstractA marine cyanobacterium, Anabaena sp. TU37‐1, exhibited stable production of hydrogen and oxygen in closed vessels. About 8.4 and 4.3 mL (at atmospheric pressure) of hydrogen and oxygen accumulated, respectively, in flasks with 20 mL gas phase during 48 h incubation. Thus, concentration of H2 and O2 became 26 and 13% of the gas phase, respectively. Duration of hydrogen production was prolonged by the periodic gas replacement in the reaction vessel. The conversion efficiencies of photosynthetically active radiation (fluorescent light, 22 W/m2) to hydrogen were 2.4 and 2.2% during the initial 12‐ and 24‐h incubation periods, respectively. © 1995 John Wiley & Sons, Inc.
Preparation of immobilized enzyme with high activity using affinity tag based on proteins A and G
Authors: Kondo Akihiko , Teshima Tadanaru 
Published: December 2004

AbstractAffinity tag AG consisting of immunoglobulin G (lgG)‐binding domains of protein A from Staphylococcus aureus (EDABC) and those of protein G from Streptococcus strain G148 (C2C3) were used to facilitate immobilization of β‐galactosidase (βgal) from Escherichia coli. Poly(methylmethacrylate/N‐isopropylacrylamide/methacrylic acid) [P(MMA/NIPAM/MAA)] and poly(styrene/N‐isopropylacrylamide/methacrylic acid) [P(St/NIPAM/MAA)] latex particles, which show thermosensitivity, were used as support materals to prepare affinity adsorbents. Human γ‐globulin (HγGb), whose major fraction is lgG, was used as an affinity ligand and was covalently immobilized onto the both latex particles by the carbodiimide method under various conditions. A fusion protein, AGβgal, was immobilized at pH 7.3 by the specific binding of affinity tag to these affinity adsorbents. The amount of adsorbed AGβgal per unit amount of immobilized HγGb, namely, efficiency of ligand utilization, was strongly affected by the type of latex particles and pH value for HγGb immobilization. The efficiency of ligand utilization was maximum in the affinity adsorbents prepared at pH 6.0 to 7.0, and that in the HγGb–P(MMA/NIPAM/MAA) latex particles was high. This result could be explained by the conformation and orientation of immobilized HγGb molecules. Immobilized AGβgal retained approximately 75% of its activity in solution and the binding is stable enough to allow repeated use. These results clearly demonstrate that combination of the affinity tag AG and the affinity adsorbents, based on the thermosensitive latex particles, offers a simple and widely applicable method for preparation of immobilized enzyme with high activity. © 1995 John Wiley & Sons, Inc.
Optimum autoregulator addition strategy for maximum virginiamycin production in batch culture of Streptomyces virginiae
Authors: Yang Young Kook , Shimizu Hiroshi , Shioya Suteaki , Suga Ken‐ichi , Nihira Takuya , Yamada Yasuhiro 
Published: December 2004

AbstractVirginiae butanolides (VBs) are autoregulators of Streptomyces virginiae, which induce virginiamycin biosynthesis. Generally, autoregulators are synthesized by the microorganism itself during culture. Addition of chemically synthesized virginiae butanolide‐C (VB‐C), which is one of the VBs, can also control the induction time and the amount of virginiamycin production. The optimum concentration and shot‐feeding time of VB‐C for the maximum production of virginiamycins M and S were investigated in flasks and jar‐fermentor batch cultures. VB‐C addition later than 8 h from the start of culture induced not only virginiamycin M and S synthesis but also VB synthesis. Virginiamycin M and S production increased with the decrease of total VBs (produced VBs and added VB‐C) concentration. That is, although VBs are needed to induce virginiamycin M and S synthesis, the amount of VB‐C added should be such that as small an amount as possible of VBs is synthesized to achieve the maximum production of virginiamycins M and S. However, the VB‐C addition earlier than 8 h from the start of culture showed no clear relationship between the amounts of VBs and virginiamycins M and S produced. In conclusion, the maximum production of virginiamycins M and S was attained by the shot addition of 5 μg/L VB‐C at 8 h from the start of culture. The maximum value was about twofold that without VB‐C addition. The optimum addition strategy of VB‐C was confirmed by the jar‐fermentor experiments. © 1995 John Wiley & Sons, Inc.
Influence of electrostatic interactions on partitioning in aqueous polyethylene glycol/dextran biphasic systems: Part I
Authors: Schluck Andreas , Maurer Gerd , Kula Maria‐Regina 
Published: December 2004

AbstractTo study the influence of charges on the partition of solutes in aqueous two‐phase systems of polyethylene glycol and dextran, partition coefficients of dimethylaminoethyl‐dextran, trimethylamino‐dextran, and bis (α,ω)‐amino‐poly(ethylene glycol) were determined as a function of pH (range 2 to 12) and ionic strength. These polymers are derivatives of the phase forming components and carry ionizable groups that are charged or uncharged depending on the pH. Unexpectedly, the largest differences in the partition coefficients were found at high pH, where the modified polymers are uncharged. In addition, the partitioning of low‐molecular‐weight model compounds, ethylenediamine and iminodiacetic acid, as well as poly‐L‐lysine and poly(allylamine) was analyzed. A consistent pattern was observed in the partition of polyelectrolytes reflecting the influence of charge, but another property of aqueous phase systems unrelated to charge and changing with pH seems to be superimposed. © 1995 John Wiley & Sons, Inc.
Measuring enzyme hydration in nonpolar organic solvents using NMR
Authors: Parker M. C. , Moore B. D. , Blacker A. J. 
Published: December 2004

AbstractA very sensitive NMR method has been developed for measuring deuterated water bound to proteins suspended in nonpolar solvents. This has been used to determine the amount of bound water as a function of water activity for subtilisin Carlsberg suspended in hexane, benzene, and toluene and for α‐chymotrypsin in hexane. The adsorption isotherms for subtilisin in the three solvents are very similar showing that water activity can be usefully employed to predict the amount of water bound to proteins in nonpolar organic media. Comparison of the degree of enzyme hydration reached in nonpolar solvents with that obtained in air shows that adsorption of strongly bound water is hardly affected by the low dielectric medium, but adsorption of loosely bound water is significantly reduced. This suggests that the hydrophobic regions of the protein surface are preferentially solvated by solvent molecules, and that in a nonpolar environment formation of a complete monolayer of water over the protein surface is thermodynamically unfavorable. © 1995 John Wiley & Sons, Inc.
Two‐step immobilized enzyme conversion of cephalosporin C to 7‐aminocephalosporanic acid
Authors: Conlon Hugh D. , Baqai Javed , Baker Kerry , Shen Yong Q. , Wong Bing L. , Noiles Ray , Rausch Carl W. 
Published: December 2004

AbstractThe first large‐scale production of 7‐aminocephalosporanic acid (7ACA) from cephalosporin C (CPC) using a wholly enzymatic synthesis method is reported here. We produced 7ACA from CPC in as high a molar yield as 85% using the immobilized enzymes D‐amino acid oxidase (D‐AOD) and glutaryl‐7‐ACA acylase (GL‐acylase). In the first reactor, CPC is converted to keto‐adipyl‐7‐aminocephalosporanic acid (keto‐7ACA) using an immobilized D‐AOD isolated from a yeast, Trigonopsis variabilis. The keto‐7ACA is then spontaneously converted to glutaryl‐7‐aminocephalosporanic acid (GL‐7ACA) via a chemical reaction with hydrogen peroxide. The hydrogen peroxide is also a product of the D‐AOD reaction. Near quantitative conversion of the keto‐7ACA to GL‐7ACA was observed. The second reactor converts GL‐7ACA to 7ACA using an immobilized GL‐acylase, which was isolated from a reconbinant Escherichia coli. The final 7ACA crystalline product is a high quality product. The reactions are conducted under very mild aqueous conditions: pH 8.0 and 20° to 25°C. The production of desacetyl side products is minimal. This process is currently being implemented on an industrial scale to produce 7ACA. © 1995 John Wiley & Sons, Inc.
Conversion of native lignin to a highly phenolic functional polymer and its separation from lignocellulosics
Authors: Funaoka M. , Matsubara M. , Seki N. , Fukatsu S. 
Published: December 2004

AbstractAn original reaction system (the phase separative reaction system) has been designed for derivatizing native lignins to highly phenolic, functional polymers. This system is composed of a phenol derivative and concentrated acid, which are not miscible at room temperature. The key point of the lignin functionalization process, including the phase separative system, is that lignin and carbohdrates, which are totally different in structures and reactivitie, are modified individually in the different phases: lignin is present in the organic phase and carbohydrates in the aqueous phase. Through the process, lignin was modified selectively at Cα‐positions of side chains, the most reactive sites, to give highly phenolic, light‐colored, diphenylmethane‐type materials which still retained original interunit linkages formed by the dehydrogenative polymerization during the biosynthesis. The carbohydrates were swollen, followed by partial hydrolysis and dissolution in the acid solution, resulting in the perfect decomposition of interpenetrating polymer network structures in the cell wall. Therefore, the functionalization of lignin and the separation of resulting lignin from carbohydrates were quickly achieved at room temperature, independent of wood species. This process would be a powerful tool for estimating strutures and reactivities of lignins as well as the functionalization of lignins, because of the selective structural modifications. © 1995 John Wiley & Sons, Inc.
Hyphal growth and fragmentation of Penicillium chrysogenum in submerged cultures
Authors: Nielsen Jens , Krabben Preben 
Published: December 2004

AbstractA previously derived population model describing the average properties of hyphal elements in submerged cultures of filamentous fungi was revised, and a term for the influence fo spore germination on the average total hyphal length was added. The model was derived from a general balance for the distribution function for the hyphal elements. Based on experimental data and the derived model, simple kinetic expressions for spore germination, tip extension, branching, and hyphal break‐up were set up. It is concluded that spore germination can be quantified by three parameters: (1) the time at which spore germination is initiated, (2) the time at which spore germination terminates, and (3) the fraction of viable spores in a spore suspension. The frequency of spore germination can be described with the B‐distribution. For growth kinetics it is concluded that the branching frequency is closely correlated with the total hyphal length and that the average tip‐extension rate can be described with saturation kinetics with respect to the hyphal length. Finally, the rate of fragmentation is linearly related to the energy input to the bioreactor, and related to the effective hyphal length. © 1995 John Wiley & Sons, Inc.
Biocatalytic synthesis of acrylates in organic solvents and supercritical fluids: III. Does carbon dioxide covalently modify enzymes?
Authors: Kamat Sanjay , Critchley Glenn , Beckman Eric J. , Russell Alan J. 
Published: December 2004

AbstractWe have previously demonstrated that the activity of the lipase (Candida cylindracea) catalyzed transesterification reaction between methylmethacrylate and 2‐ethylhexanol in supercritical carbon dioxide is comparatively low. In this article, we have investigated the same reaction in supercritical carbon dioxide with a special emphasis on determining the extent of any interaction between the enzyme and carbon dioxide. Transesterification reaction rates in hexane and supercritical carbon dioxide are compared at different temperatures. In supercritical carbon dioxide, temperature was found to have no significant effect on reaction rate in the range of 40° to 55°C. Above 55°C, however, the reaction rate increased significantly as a function of temperature. It appears that carbon dioxide forms reversible complexes with the free amine groups on the surface of the enzyme. Direct evidence of modification was obtained using mass spectroscopy to detect the extent of modification of a pure protein. The kinetics of the reaction have been studied in hexane, and they obey a ping‐pong bi–bi mechanism with inhibition by 2‐ethylhexanol. The effect of bubbling carbon dioxide and/or fluoroform on the reaction rate in hexane at different temperatures suggests that the enzyme undergoes shear inactivation in hexane. © 1995 John Wiley & Sons, Inc.
Fundamental denitrification kinetic studies with Pseudomonas denitrificans
Authors: Wang J.‐H. , Baltzis B. C. , Lewandowski G. A. 
Published: December 2004

AbstractFundamental kinetic studies on the reduction of nitrate, nitrite, and their mixtures were performed with a strain of Pseudomonas denitrificans (ATCC 13867). Methanol served as the carbon source and was supplied in excess (2:1 mole ratio relative to nitrate and/or nitrite). Nitrate and nitrite served as terminal electron acceptors as well as sources of nitrogen for biomass synthesis. The results were explained under the assumption that respiration is a growth‐associated process. It was found that the sequence of complete reduction of nitrate to nitrogen gas is via nitrite and nitrous oxide.It was found that the specific growth rate of the biomass on either nitrate or nitrite follows Andrews inhibitory kinetics and nitrite is more inhibitory than nitrate. It was also found that the culture has severe maintenance requirements which can be described by Herbert's model, i.e., by self‐oxidation of portions of the biomass. The specific maintenance rates at 30°C and pH 7.1 were found to be equal to about 28% of the maximum specific growth rate on nitrate and 23% of the maximum specific growth rate on nitrite. Nitrate and nitrite were found to be involved in a cross‐inhibitory noncompetitive kinetic interaction. The extent of this interaction is negligible when the presence of nitrite is low but is considerable when nitrite is present at levels above 15 mg/L.Studies on the effect of temperature have shown that the culture cannot grow at temperatures above 40°C. The optimal temperature for nitrate or nitrite reduction was found to be about 38°C. Using an Arrhenius expression to describe the effect of temperature on the specific growth rates, it was found that the activation energy for the use of nitrate by the culture is 8.6 kcal/mol and 7.21 kcal/mol for nitrite. Arrhenius‐type expressions were also used in describing the effect of temperature on each of the parameters appearing in the specific growth rate expressions. Studies on the effect of pH at 30°C have shown that the culture reduces nitrate optimally at a pH between 7.4 and 7.6, and nitrite at a pH between 7.2 and 7.3. © 1995 John Wiley & Sons, Inc.
A comparison of lipase‐catalyzed ester hydrolysis in reverse micelles, organic solvents, and biphasic systems
Authors: Yang Fangxiao , Russell Alan J. 
Published: December 2004

AbstractThe performance of lipases from Candida rugosa and wheat germ have been investigated in three reaction media using three acetate hydrolyses as model reactions (ethyl acetate, allyl acetate, and prenyl acetate). The effect of substrate properties and water content were studied for each system (organic solvent, biphasic system, and reverse micelles). Not unexpectedly, the effect of water content is distinct for each system, and the optimal water content for enzyme activity is not always the same as that for productivity. A theoretical model has been used to simulate and predict enzyme performance in reverse micelles, and a proposed partitioning model for biphasic systems agrees well with experimental results. While the highest activities observed were in the micellar system, productivity in microemulsions is limited by low enzyme concentrations. Biphasic systems, however, support relatively good activity and productivity. The addition of water to dry organic solvents, combined with the dispersion of lyophilized enzyme powders in the solvent, resulted in significant enzyme aggregation, which not surprisingly limits the applicability of the “anhydrous” enzyme suspension approach. © 1995 John Wiley & Sons, Inc.