bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nature of yeast cells immobilized by radiation polymerization. Activity dependence on the water content of polymer carriers
Authors: Fujimura T. , Kaetsu I. 
Published: December 2004

AbstractHigher activity of ethanol production due to higher density of yeast cells was observed in yeast cells immobilized with artificial polymer carriers of higher water content based on methoxypolyethyleneglycol methacrylate and 2‐hydroxyethylacrylate. These polymer carriers were prepared by radiation‐induced polymerization below 0°C. Yeast cells were immobilized with these carriers by adsorption method during multiplication. Two possible reasons for higher activity were discussed.
Steam pretreatment of lignocellulosic material for enhanced enzymatic hydrolysis
Authors: Brownell Harold H. , Saddler John N. 
Published: December 2004

AbstractPretreatment methods were compared with steam explosion, and differing views on the relative importance of mechanical and chemical effects were outlined. Hydrolysis was desirable; pyrolysis was undesirable. The effects of initial moisture content on steam consumption, mechanism and rate of heat transfer, pentosan solubilization, and subsequent glucose yield were summarized. The insignificant effect, after treatment at 240°C, of 90% pressure bleed‐down before explosion on subsequent simultaneous saccharification and fermentation (SSF) yields was described. Treatment at 190°C with complete bleed‐down (no explosion), when compared with that at 240°C with explosion from full pressure, showed at least as good solubilizatoin of pentosan, enzymatic hydrolysis, and SSF but showed greater pentosan destruction for the same degree of pentosan removal. Water washing of unexploded steamed aspenwood chips was at least as efficient as that of similarly treated but exploded chips. Scanning electron micrographs of unexploded chips showed extensive rupturing of vessel pit membranes and other morphological features associated with steam‐exploded wood. Neither the explosion nor the high temperatures (above 190°C) are necessary.
Immobilization of cellulolytic and hemicellulolytic enzymes on inorganic supports
Authors: Shimizu K. , Ishihara M. 
Published: December 2004

AbstractCommercial cellulase preparations from Trichoderma viride and Aspergillus niger were immobilized on porous silica glass and ceramics such as alumina and titania with titanium tetrachloride (TiCl4) and on their silanized derivatives with glutaraldehyde (GLUT). The amounts of the immobilized enzymes were in the range 10–50 mg/g carrier (dry) depending on the kind of carrier and immobilization method. Their activities toward carboxymethyl cellulose (CMC), xylan, aryl‐β‐glucoside, and aryl‐β‐xyloside were 3–53% of those of the native enzymes. The optimum pH of the enzymes shifted to the acidic side in most cases, whereas the optimum temperatures were nearly the same as those of native ones. The activity of immobilized enzyme preparations towards CMC did not change significantly during continuous operation over a periods of 60 days. Finally, xylan was hydrolyzed with the immobilized enzymes, and the sugars formed were investigated.
Single‐cell protein from methanol with Enterobacter aerogenes
Authors: Gnan Said Omar , Abodreheba Ali Omar 
Published: December 2004

AbstractAn identifiedEnterobacter aerogenesutilizing methanol as a sole carbon source was studied for the optimization of biomass production and the reduction of its nucleic acid content. Results indicated that the highest yield and conversion were obtained at 0.5% methanol. The addition of seawater as a source of trace elements has an adverse effect. However, the addition of urea as source of nitrogen enhanced the growth of E. aerogenes. Heat shock at 60°C for 1 min followed by incubation at 50°C for 2 h caused 72.6% reduction in the nucleic acid.
Inhibition or initiation of a radical polymerization reaction by an ultraviolet‐induced enzymatic process
Authors: Van Deynse D. , Desie G. , De Schryver F. C. , Leenders L. 
Published: December 2004

Abstractα‐Chymotrypsin was modified to a light‐controllable enzyme derivative by acylating active serine 195 residue with a cinnamoyl group or analogue. Upon UV irradiation the acylgroup could be isomerized, leading to release of the inhibiting group. Enzymatic activity could thus be regulated by means of UV light. A full 100% inhibition of the enzymatic activity could not be reached by the cinnamoyl derivative. Only posttreatment with diisopropylfluorophosphate yields a fully inactive enzyme derivative. The shelf‐life of the inhibited enzyme was rather poor. Only freeze‐dried samples could be used for several months without significant recovery of activity. Adapting the sensitivity of the system to visible light seems limited to the size of an enzyme's active site. Combination of the enzymatic system producing an inhibitor or an initiator with a polymerization reaction can result in a photographic process with a higher amplification factor.
Growth and enzyme synthesis during continuous culture of Trichosporon cutaneum on phenol
Authors: Spånning Åke , Neujahr Halina Y. 
Published: December 2004

AbstractThe soil yeast Trichosporon cutaneum was grown in continuous culture with phenol as the sole carbon source. The cultures were operated as carbon‐limited chemostats or as steady‐state continuous cultures without carbon limitation. Selected comparative runs were also conducted on glucose or acetate as carbon source. In addition to growth parameters, the activities of several intracellular enzymes were determined, comprising those directly involved in the degradation of phenol as well as auxiliary enzymes required for the generation of reducing power. All enzymes were assayed in detergent‐permea‐bilized cells. Phenol was found to serve as an excellent carbon source, comparable to glucose or acetate. The utilization of phenol in T. cutaneum is very efficient as indicated by a low maintenance requirement (0.01 g phenol/g cells·h). The cell yields obtained were on the order of 0.8 g cells/g phenol. Although the phenol‐limited chemostats were run with fully phenol‐induced cells, a further increase in the activities of isocitrate DH(NADP+), maleate DH and the phenol‐degrading enzymes occurred after transition to nonlimiting condition. Enzyme activities increased in parallel with increasing phenol levels in the effluent, as well as with increasing toxicity. The significance of this phenomenon is discussed. The significance of this phenomenon is discussed. This elevation in enzyme activities in not related to an increase in specific growth rate.
Analysis of the productivity of a continuous algal culture system
Authors: Radmer R. , Behrens P. , Arnett K. 
Published: December 2004

AbstractWe describe a first‐principles analysis of a system for the continuous culture of the green alga Scenedesmus obliquus under light‐limiting conditions. According to this analysis, the productivity of the algal culture is given by the relation Y = EmI0AK(1 – e−αcl) – GRcV, where Y = yield (g cells/h), Em = 0.20 (the maximum attainable photosynthetic conversion on an energy basis), A = illuminated area (m2), K = 0.156[(g cells/h/W), the energy equivalent of the algae], I0 = light intensity (W/m2), α = extinction coefficient (L/cm/g),c = cell concentration (g/L), I = light path (cm), R = respiration rate (g carbon/g cells/h), V = culture volume (L), and G = ratio of g cells to g carbon (2.04). This formula is completely determined and has no free adjustable parameters. Using parameter values determined independently, the model accurately predicted the relationship of productivity to cell density in the culture system.
Improvement of product yields by temperature‐shifting of Escherichia coli cultures containing plasmid pOU140
Authors: diPasquantonio Vincent M. , Betenbaugh Michael J. , Dhurjati Prasad 
Published: December 2004

AbstractTemperature shifting was investigated as a means of improving cloned‐gene product yields form a recombinant Escherichia coli containing the temperature‐sensitive plasmid, pOU 140. In a series of shaker flask fermentations recombinant cells were thermally induced for different time periods. The growth, stability, and plasmid product levels were followed, and the results indicate the existence of an induction time period that maximizes product yield. A sustained thermal induction results in recombinant cell death and instability, while exposure to a runaway temperature for minimal time periods does not give sufficiently high product yields. At intermediate cycling times, however, the recombinant cells remain stable, and the plasmid replication region is activated, resulting in higher product yields.
Glucose oxidation in a dual hollow fiber bioreactor with a silicone tube oxygenator
Authors: Chang Ho Nam , Kyung Yun‐Seung , Chung Bong Hyun 
Published: December 2004

AbstractA dual hollow fiber bioreactor, consisting of an outer silicone membrane for oxygen supply and an inner polyamide membrane for substrate permeation, was used as an immobilized enzyme reactor to carry out enzymatic glucose oxidation. Attaching a silicone tube oxygenator to provide an additional oxygen supply improved the conversion in glucose oxidation when the oxygen supply was rate‐limiting. The reactor was operated in both diffusion and ultrafiltration modes. In the latter case, the conversion was much higher, but the stability of the immobilized enzyme was better maintained in the diffusion mode. As the inlet glucose concentration increased from 10mM to 500mM, the conversion decreased from 70 to 20%.
Methane recovery from water hyacinth through whole‐cell immobilization technology
Authors: Annachhatre A. P. , Khanna P. 
Published: December 2004

AbstractThe concepts of feed pretreatment, phase separation, and whole‐cell immobilization technology have been incorporated in this investigation for the development of rational and cost‐effective two‐ and three‐stage methane recovery systems from water hyacinth (WH)Analyses of laboratory data reveal that a three‐stage system could be designed with an alkali pretreatment stage [3.6% Na2CO3 + 2.5% Ca(OH)2 W/W, 24 h HRT] followed by an open acid reactor (2.1 days HRT) and closed immobilized methane reactor (12 h HRT), providing steady‐state COD conversion of 62–65%, TVA conversion of 91–95%, and gas productivity of 4.08–5.36 L/L reactor volume/day with 82% methane. A gas yield of 50 L/kg WH/day (dry wt basis) at 35–37°C is possible with this system. Insulation bricks, with particle size distribution of 500–3000 μm, were used as support material in the reactors at organic loading rate of 20 kg COD/m3 day. The reactors matured in 15–18 weeksSubstantial reduction in retention time for the conversion of volatile acids in immobilized methane reactors prompted further research on the combined immobilized reactor to make possible an additional reduction in the cost of a WH‐based biogas system. Evaluation of laboratory data reveals that a two‐stage system could be designed with an open alkali pretreatment stage and a combined immobilized reactor (12 h HRT), providing steady‐state COD conversion of 53% and gas productivity of 3.1 L/L reactor volume/day with 86% methane. A gas yield of 44 L/kg WH/day (dry wt basis) at 35–37°C could be obtained from this system. Insulation bricks, with 500–1000 μm particle size distribution, was used as support material at an organic loading rate of 15 kg COD/m3 day. Notwithstanding the fact that the technology in this study has been developed with water hyacinth as substrate, the implicit principles could be extended to any other organic substrate.
Polymerization of phenols catalyzed by peroxidase in nonaqueous media
Authors: Dordick Jonathan S. , Marletta Michael A. , Klibanov Alexander M. 
Published: December 2004

AbstractPolymers produced by horseradish‐peroxidase‐catalyzed coupling of phenols have been explored as potential substitutes for phenol‐formaldehyde resins. To overcome low substrate solubilities and product molecular weights in water, enzymatic polymerizations in aqueous‐organic mixtures have been examined. Peroxidase vigorously polymerizes a number of phenols in mixtures of water with water‐miscible solvents such as dioxane, acetone, di‐methylformamide, and methyl formate with the solvent content up to 95%. As a result, various phenolic polymers with average molecular weights from 400 to 2.6 × 104 D were obtained depending on the reaction medium composition and the nature of the phenol. Peroxidase‐catalyzed copolymerization of different phenols in 85% dioxane was demonstrated. Poly(p‐phenylphenol) and poly(p‐cresol) were enzymatically prepared on a gram scale. They had much higher melting points, and in addition, poly(p‐phenylphenol) was found to have a much higher electrical conductivity than phenol‐formaldehyde resins.
Mixing and power characteristics of drag board device in shallow pool
Authors: Cárdenas A. , Markovits A. 
Published: December 2004

AbstractMixing and stirring of a 20‐m2 shallow pool by means of a drag board device has been investigated. The board closes the pool cross section except for a slit of a few centimeters above the bottom, and it is slowly moved back and forth, forcing the water to run through the slit and thereby creating a turbulent backwhirl. Power drawn and the drag on the board has been measured together with the velocities of the water at different locations in the wake of the board. Power number Np has been correlated with the Reynolds NRe and the bottom clearance numbers Nc by the expressions

Power and Reynolds numbers are defined as usual with the square root of the board‐immersed‐area as the characteristic length. The bottom clearance number is defined as the ratio of the water depth in the pool to the difference between water depth and the board width immersed in water. Flow pattern behind the board consists of large vortex loops causing the fluid to circulate from bottom to top and producing a thorough mixing effect. The drag board seems to have several advantages over conventional paddle wheels for the mixing and stirring of algal cultures in shallow ponds.
Reaction properties of hydrophobic enzymes and their immobilization on phospholipid composite membranes
Authors: Sada Eizo , Katoh Shigeo , Terashima Masaaki , Kikuchi Yasufumi 
Published: December 2004

AbstractReaction rates of hydrophobic enzymes, aminopeptidase, and alkaline phosphatase, in microsomes prepared from the porcine brush border membrane and in vesicles pre pared from microsomes and phospholipids were measured at various temperatures. Interactions between the hydrophobic enzymes and the phospholipid layers are discussed as well as the effects of fluidity change of phospholipid layers on enzyme activity. Further, reaction properties and stabilities of the immobilized vesicles containing microsomal enzymes were studied.
An investigation of a fertilizer–tap water medium for mass algal production in outdoor plastic‐enclosed systems
Authors: Geldenhuys D. J. , Walmsley R. D. , Toerien D. F. 
Published: December 2004

AbstractThe feasibility of using two fertilizers (urea plus superphosphate) in tap water as a medium for the mass culture of green algae (Scenedesmus and Ankistrodesmus) in outdoor plastic‐enclosed minipond systems was investigated. Experiments in which the basic fertilizer‐tap water medium was enriched with micro‐ and/or macronutrients revealed no nutrient deficiency symptoms in the algal biomass produced. Biomass production was found to be quantitatively related to the concentration of fertilizer added and maximal production (> 15 g/m2 day) was achieved following the addition of 30 mg N/L (1.89 g N/m2 day) and 4.5 mg P/L (0.28 g P/m2/day).
Amylolysis of raw corn by Aspergillus niger for simultaneous ethanol fermentation
Authors: Han Inyee Y. , Steinberg M. P. 
Published: December 2004

AbstractThe novelty of this approach was hydrolysis of the raw starch in ground corn to fermentable sugars that are simultaneously fermented to ethanol by yeast in a non‐sterile environment. Thus, the conventional cooking step can be eliminated for energy conservation. A koji of Aspergillus niger grown on whole corn for 3 days was the crude enzyme source. A ratio of 0.2 g dry koji/g total solids was found sufficient. Optimum pH was 4.2. Ethanol concentration was 7.7% (w/w) in the aqueous phase with 92% raw starch conversion. Agitation increased rate. Sacharification was the rate‐limiting step. The initial ethanol concentration preventing fermentation was estimated to be 8.3% by weight.
Adsorption and kinetic behavior of purified endoglucanases and exoglucanases from Trichoderma viride
Authors: Beldman G. , Voragen A. G. J. , Rombouts F. M. , Searle‐van Leeuwen M. F. , Pilnik W. 
Published: December 2004

AbstractAdsorption on crystalline cellulose of six endoglucanases (Endo I, II, III, IV, V and VI; 1, 4‐β‐D‐glucan glucanohydrolase, EC 3.2.1.4) and two exoglucanases (Exo II and III; 1,4‐β‐D‐glucan cellobiohydrolase, EC 3.2.1.92), purified from a commercial cellulase preparation of Trichoderma viride origin, was studied. Endo I, III, and V adsorbed strongly on Avicel cellulose, while adsorption of Endo II, IV, and VI was much lower. Also, the two exoglucanases could be divided into one enzyme (Exo III) that had a high adsorption affinity and another enzyme (Exo II) that adsorbed only moderately. Adsorption data fitted the Langmuir‐type adsorption isotherm. However, adsorption was only partially reversible with respect to dilution. No relation could be found between adsorption affinity and degree of randomness in cellulose hydrolysis, measured as the diversity of released hydrolytic products. Kinetic measurements indicated that only part of the adsorbed enzyme molecules are hydrolytically active.
Influence of very small bubbles on kLa measurement in viscous microbiological cultures
Authors: Kawase Y. , Moo‐Young M. 
Published: December 2004

AbstractIn gas–liquid dispersions based on viscous non‐Newtonian fluids, numerous very small bubbles are formed due to their high residence times in contacting devices such as bubble columns. The influence of these small bubbles on the measurement of the volumetric mass transfer coefficient in the contactor by the dynamic CO2 gas analysis method is discussed. It is found that their effect on this measuring technique is insignificant compared to that when using the conventional dissolved‐oxygen technique.
The pH mediated effects of initial glucose concentration on the transitory occurrence of extracellular metabolites, gas exchange and growth yields of aerobic batch cultures of Klebsiella pneumoniae
Authors: Iversen J. J. Lønsmann 
Published: December 2004

AbstractThe changes in growth kinetics in aerobic batch cultures of Klebsiella pneumoniae were followed by measurements of extracellular metabolites, rates of gas exchange, dissolved oxygen tension, pH, and carbon balance at all stages of growth. When the initial growth‐limiting glucose concentration in media without pH control was increased from 1.0 g carbon L−1 to 2.2 g carbon L−1, the number of different, mainly acidic, extracellular metabolites of glucose at the end of exponential growth increased, while the proportion of acetate decreased. During the postexponential growth phase, the extracellular metabolites were oxidized, resulting in an increasing complexity of changes in pH, gas exchange, and dissolved oxygen tension with increasing initial substrate concentration. All these parameters showed concomitant stepwise changes. This pattern was independent of the dissolved oxygen tension in the range 30–200 μM. When pH was kept constant, the number, slope, and relative magnitude of the steps in gas exchange and dissolved oxygen tension were pH‐dependent, being most complex at low pH. Detailed carbon balances showed that 20% of the initial glucose was converted into extracellular metabolites at the end of exponential growth at neutral pH. In the postexponential phase, pyruvate (2%) was reoxidized first followed by acetate (13%). The observed molar growth yield coefficient (YATP) was 8.4 if the transitory occurrence of pyruvate and acetate was accounted for, and 6.4 if it was neglected. The corrected observed molar growth yield coefficient (Y′ATP) was 9.4 and compared well with the true molar growth yield coefficient (Y), which was found to be 11.0. Specific in situ respiration rates of the exponential growth phase of cultures grown at different controlled pH values compared well with in situ values for energy‐limited chemostat grown cells at the same growth rates, suggesting that growth in the batch culture was energy‐limited throughout the exponential growth phase. This view was supported by low levels of intracellular glycogen and exopolysaccharides of all cultures, by the value of Y′ATP of 9.4, and by a constant specific production rate of the extracellular metabolites throughout exponential growth. It was concluded that even under strictly aerobic conditions, control of pH is as important as control of dissolved oxygen tension during growth of enterobacteriaceae in batch cultures.
Dynamics of chemostat in which one microbial population grows on multiple complementary nutrients
Authors: Pavlou Stavros 
Published: December 2004

AbstractThe equations of a chemostat in which one microbial population grows on multiple rate‐limiting nutrients are formulated. The dynamics of a chemostat involving growth on complementary nutrients is studied through stability analysis of the system of equations. Some conditions are derived that relate the dynamic behavior of the chemostat to its operating conditions and can be applied to any model for the specific growth rate of the population. It is shown that, if maintenance of the population is neglected, the system exhibits no sustained or damped oscillations. If maintenance of the population is considered, damped oscillations are observed for some operating conditions.
Performance evaluation of ethanol fermentor systems using a vector‐valued objective function
Authors: Tsuji Satoshi , Shimizu Kazuyuki 
Published: December 2004

AbstractIt is shown that the performance evaluation using a vector‐valued objection function whose components are the product productivity, the product concentration, and the substrate conversion is quite useful in getting deeper insight into the development of new processes and in determining the operating point. Particular attention is focused on the ethanol fermentation using variety of systems such as the conventional chemostat system, multiple fermentor system, cell recycle system, extractive fermentor system, cell recycle system, extractive fermentor system, and immobilized cell system. The contour map and the projection of the noninferior set are used in investigating the performance improvement and the trade‐offs among performance indexes.
Modeling the kinetics of immobilized glucose oxidase
Authors: Parker J. W. , Schwartz C. S. 
Published: December 2004

AbstractDetermination of glucose concentrations in fluids frequently requires the application of immobilized glucose oxidase. An accurate description of the immobilized enzyme kinetics is critical for such applications. In this study, the overall rate of reaction of immobilized glucose oxidase is investigated theoretically. A novel steady‐state model based on a ping‐pong kinetic mechanism for glucose oxidase is developed. Numerical studies are used to examine the parameter sensitivity of this model. The enzyme loading, matrix thickness and geometric con figuration are found to have a significant influence on substrate uptake by insolubilized glucose oxidase.Aditionally, this new model is compared with a previously developed model based on an alternative ping‐pong kinetic mechanism. Under steady‐state conditions, no significant difference between the two models is apparent when appropriate kinetic parameters are applied to each of the models. The model developed herein is also compared with models utilizing the simplifying assumption of Michaelis–Mented kinetics for substrate reaction. Numerical studies indicate that under most realizable biological conditions, a model based on ping‐pong kinetics should be applied to accurately describe substrate uptake by immobilized glucose oxidase.