bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toxic effects of fatty acids on yeast cells: Dependence of inhibitory effects on fatty acid concentration
Authors: Hundová Z. , Fencl Z. 
Published: December 2004

AbstractThe yeasts Saccharomyces cerevisiae, Candida utilis, and Candida lipolytica were used to investigate the action of different concentrations of fatty aeids (from acetic to myristic acid) on cell growth, division, uptake of inorganic phosphate, and substrate oxidation. The former two yeasts were found to undergo an inhibition of growth, cell division, and phosphate uptake at lower acid concentrations and to experience the inhibition of substrate oxidation at higher acid concentration. The concentration dependence of the action of fatty acids can be classified into four categories: (1) subthreshold concentrations which do not inhibit growth and have either no effect on, or stimulate, oxygen consumption; (2) threshold concentrations which lower the rate of growth, cell division, and phosphate uptake but do not inhibit the oxidation of carbon substrate; (3) above threshold concentrations which inhibit partially even substrate oxidation, and (4) microbicide concentrations. Candida lipolytica displays the Same sensitivity toward the action of fatty acids as the above yeast species; however, the threshold concentrations are higher and can be quickly lowered owing to oxidation by the yeast. The concentrations of fatty acids found in the medium after cultivations of yeast with n ‐alkanes are of the same order as limiting concentrations; the formation of acids with twelve and less carbons in the molecule can thus be assumed to be one of the basic reasons for the lowering of biomass yields during cultivations on these hydrocarbons.
Application of cyanide‐metabolizing enzymes to environmental control; enzyme thermistor assay of cyanide using immobilized rhodanese and injectase
Authors: Mattiasson Bo , Mosbach Klaus , Svenson Anders 
Published: December 2004

AbstractThe application of the enzyme thermistor in the analysis of cyanide in standard solutions as well as in blast furnace waste water is described. The heat signal is generated in the conversion of cyanide, catalyzed by the immobilized enzymes rhodanese (E.C. 2.8.1.1) and injectase (E.C. 4.4.19). Using the combination of cyanide‐metabolizing enzymes and the enzyme thermistor unit, assays down to 20μM cyanide can be carried out. Linear relationships were obtained at 20–600μM cyanide for injectase and 20–1000μM for rhodanese. The stability at 27°C of the heat response was initially decreased, but soon stabilized at about 80% of the initial value and remained so for at least 200 hr. The technique was easily adapted to continuous analysis, applicable to environmental control (e.g., a “cyanide guard”) with a response time at present within 2–3 min after a sudden change in cyanide concentration has appeared.
Transfer function matrix of the continuous cultivation system of Morchella crassipes in ammonia base waste sulfite liquor
Authors: Leduy A. , Kosaric N. , Zajic J. E. 
Published: December 2004

AbstractA continuous stirred tank fermentor (CSTF) used for cultivation of the fungus Morchella crassipes in ammonia base waste sulfite liquor (NH3‐WSL) was considered as a multivariable linear system around its operating point. Pulse testing on the inputs (inlet jacket temperature, inlet pH, inlet substrate concentration) and their responses at the outputs (biomass, outlet temperature, outlet jacket temperature, outlet pH, outlet substrate concentration) were used for numerical determination of the transfer function matrix:
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Application of immobilized chymotrypsin in a multistage fluidized‐bed reactor
Authors: Halwachs W. , Wandrey C. , Schügerl K. 
Published: December 2004

AbstractThe stereospecific hydrolysis of D,L‐phenylalanine methylester with immobilized α‐chymotrypsin was carried out as a model reaction for the racemate resolution of aromatic amino acids in a five staged fluidized‐bed reactor (FBR). Owing to ester hydrolysis, a pH shift occurred along the reactor. Because of the pH‐dependent enzyme activity a particular longitudinal pH profile had to be enforced by a proper entrance pH in order to gain an optimum conversion. In the FBR with optimum pH profile, higher conversions were achieved than in a continuous stirred tank reactor (CSTR) at the pH optimum and at the same contact time. By the application of a proton balance and the results of kinetic measurements a model was developed for the prediction of the optimum longitudinal pH profile with regard to the maximum conversion.
Preparation and properties of immobilized papain and lipase
Authors: Kilara A. , Shahani K. M. , Wagner Fred W. 
Published: December 2004

AbstractPapain and lipase were immobilized on derivatized Sepharose 4‐B. The activated agarose had a binding capacity of 1.2 μmol amino groups/ml packed agarose or 17 mg proteins/g dry agarose. The immobilized enzyme preparations were tested for the effects of pH of assay, temperature of assay, and substrate concentrations. The effect of 6M urea on the activity of papain was also determined. Soluble forms of the enzymes were used for comparison. Immobilization of the enzymes resulted in slightly different pH and temperature optima for activities. For immobilized papain Km (app) was similar to the one observed with soluble papain. Immobilization of lipase, however, caused a decrease in Km values. The immobilized enzyme preparations were stable when stored at 4°C and pH 7.5 for periods up to eight months. The soluble enzymes lost their activity within 96 hr under similar storage conditions. Immobilized papain did not lose any activity after treatment with 6M urea for 270 min, whereas soluble papain lost 81% of its activity after the urea treatment, indicating that the immobilization of papain imparted structural and conformational stability to this enzyme.
Effect of mass transfer resistance on the lineweaver–burk plots for flocculating microorganisms
Authors: Ngian K. F. , Lin S. H. , Martin W. R. B. 
Published: December 2004

AbstractIt is shown that the mass transfer resistance can significantly distort the linearity of the Lineweaver–Burk plot of the kinetic data for a microbial culture which forms aggregates. For small flocs, the linearity of the Lineweaver–Burk plot is largely retained, but a different slope and intercept will be obtained compared with flocs free from mass transfer resistance. For large flocs, the Lineweaver–Burk plot shows pronounced curvature at high limiting substrate concentrations. Hence, if the true intrinsic kinetic parameters are to be extracted from a highly flocculating microbial culture, sufficient agitation has to be provided to remove the effect of mass transfer resistance. If the behavior of the flocculating microbial culture is to be explored, additional values for some physical parameters, such as the effective diffusion coefficient of the substrate in floc, the floc density, and the mean floc radius, are needed.
Practical identifiability of growth and substrate consumption models
Authors: Nihtilä Markku , Virkkunen Jouko 
Published: December 2004

AbstractThe estimation of parameters in several dynamic models, which describe growth and substrate consumption, has been carried out using a modified Gauss–Newton‐type method. The four models considered are Monod, Contois, linear specific growth rate, and an enzyme kinetic model. The initial values of the differential equations are included in the parameter vector which will be estimated. The efficiency of the method and the confidence limits of the parameters were studied using simulated measurement noise. The experimental results describeTrichoderma viridegrowing on glucose as the main carbon source.
Selection of a chemically defined medium for submerged cultivation of Streptomyces aureofaciens with high extracellular caseinolytic activity
Authors: Laluce Cecilia , Molinari Rubens 
Published: December 2004

AbstractA chemically defined medium was developed for the submerged cultivation of Streptomyces aureofaciens with a high secretion of caseinolytic activity. The medium composition is: 40 g/liter maltose; 1.640 g/liter L‐leucine (0.0125M); 1.765 g/liter L‐lysine (0.0125M); 6.976 g/liter K2HPO4(0.04M); 4 g/liter CaCO3; 0.2 g/liter MgSO4·7H2O; 0.01 g/liter ZnSO4·7H2O; 0.01 g/liter FeSO4·7H2O; 0.01 g/liter. MnSO4·H2O, and 0.005 g/liter CoSO4·7H2O. Quantitative correlations were established between the concentrations of nutrients in the medium and the secretion of proteolytic activity. In this medium the secretion of proteolytic activity parallels growth, reaching a maximum after 70 hr at 30°C in shaker cultures. The secretion appears to be an active process and to require aerobic conditions.
Preparation and properties of proteases immobilized on anion exchange resin with glutaraldehyde
Authors: Ohmiya Kunio , Tanimura Shuya , Kobayashi Takeshi , Shimizu Shoichi 
Published: December 2004

AbstractHigh activity alkaline protease was obtained when the enzyme was immobilized on Dowex MWA‐1 (mesh 20–50) with 10% glutaraldehyde in chilled phosphate buffer (M/15, pH 6.5). Activity yields of the protease and rennet were 27 and 29, respectively. The highest activities appeared at 60°C, pH 10 for alkaline protease and 50°C, pH 4.0 for rennet. The properties of both proteases were not essentially changed by the immobilization except that the Km values of both enzymes were increased about tenfold as a result of immobilization. Both proteases in the immobilized state were more stable than those in the free state at 60°C. Other peptide hydrolases, β‐galactosidase, invertase, and glucoamylase, were successfully immobilized with high activities, but lipase, hexokinase, glucose‐6‐phosphate dehydrogenase, and xanthine oxidase became inactive.
Continuous dehydrogenation of a steroid with immobilized microbial cells: Effect of an exogenous electron acceptor
Authors: Yang Ho Seung , Studebaker Joel F. 
Published: December 2004

AbstractWhole cells of Pseudomonas testosteroni, induced to synthesize steroid‐transforming enzymes beforehand, have been immobilized by entrapment in polyacrylamide gel. The immobilized cells have then been used to catalyze the continuous Δ1‐dehydrogenation of Reichstein's substance S under various conditions in the presence of phenazine methosulfate (PMS), an electron acceptor for the cell‐free Δ1‐dehydrogenase. The presence of PMS substantially increases the rate of reaction when fed with the steroid substrate to a continuous stirred tank reactor containing the immobilized cells. The operational half‐life of the Δ1‐dehydrogenase activity of the cells, about 103 hr under the best operating conditions, is essentially unaffected by the presence of PMS. Though the acceleration of the reaction may be due to PMS‐mediated passage of electrons from some component in the electron transport chain to molecular oxygen, the lack of a similar effect with methylene blue is consistent with the conclusion that PMS functions directly as the electron acceptor for the Δ1‐dehydrogenase.
Determination of redox potential levels critical for cell respiration and suitable for L‐leucine production
Authors: Akashi Kunihiko , Ikeda Shigeho , Shibai Hiroshiro , Kobayashi Kaetsu , Hirose Yoshio 
Published: December 2004

AbstractThe effect of oxygen supply on L‐leucine fermentation was investigated employing a leucine‐producing mutant of Brevibacterium lactofermentum. Since it was not possible to measure oxygen tension below 0.01 atm by a Teflon‐coated oxygen electrode, the degree of satisfaction of the cells' oxygen demand (cells' respiration rate/maximum oxygen demand of cells, rab/KrM) and the redox potential of the culture medium (E. mV) were used as indices to oxygen supply in cultures under low oxygen tension. When the oxygen demand of the cells was satisfied (rab/KrM = 1.0) and the E value was between −90 and −110 mV, L‐leucine formation was 26.5 mg‐ml. When the oxygen demand of the cells was not satisfied (rab/KrM = 0.85) and the E value was between −200 and −220mV, L‐leucine accumulation was 29.7 mg/ml. When the oxygen supply was extremely limited (rab/KrM = 0.27) and the E value was −280 mV. L‐leucine formation was 12.9 mg/ml. A new method which simultaneously measures the redox potential and dissolved oxygen was applied to the determination of the critical dissolved oxygen level for cell respiration (PL crit), which was too small to be detected by conventional oxygen electrodes. The value of PL crit of the leucine producer was estimated as 0.0002 atm.
Disintegration of dried yeast cells and its effect on protein extractability, sedimentation property, and viscosity of the cell suspension
Authors: Lee Cherl‐Ho , Tsang Shek Kwan , Urakabe Rintaro , Rha Cho Kyun 
Published: December 2004

AbstractThe morphology of dried Candida lipolytica yeast suspended in aqueous solutions (H2O, 0.4% NaOH, 2N HCl, and 6N HCl) and organic solvents (95% alcohol and acetone) was studied using a scanning electron microscope (SEM) and an optical microscope. The effect of high‐pressure homogenization on cell‐wall structure and cell clumps was also determined. The protein extractability, sedimentation property, and viscosity of cells subjected to different mechanical and chemical treatments were also investigaged. The dried yeast cells were in a spherical agglomeration consisting of 100s of closely bound cells. The clump was resistant to water, aqueous 2N HCl solution at 25°C, 95% alcohol and acetone, but vulnerable to 6N HCl, aqueous 0.4% NaOH solution, and homogenization. The homogenization of the cell suspension not only broke the clump but also cracked the cell‐wall structure. The aqueous alkaline solution could have weakened the cell wall and increased the solubility of the protein released through the cracks in the cell wall. The destruction of the agglomeration and the cell‐wall structure increased the hydration of the cell and thereby increased the stability of the suspension. The sedimentation and the viscosity of the cell suspension corresponded to the morphological changes and the extractability of protein in the cell suspensions with different treatments.
Immobilized hydroxysteroid dehydrogenases for the transformation of steroids in water–organic solvent systems
Authors: Carrea G. , Colombi F. , Mazzola G. , Cremonesi P. , Antonini E. 
Published: December 2004

AbstractThe hydroxysteroid dehydrogenases: β‐HSDH, 20β‐HSDH, and 3α‐HSDH, were immobilized on CNBr‐activated Sepharose. The effect of various immobilization conditions on the activity recovery and stability were examined. The presence of cofactor during the immobilization reaction increased the activity recovery (40–60% of the total) and also led to materials highly stable in the presence of organic solvents. For example, β‐HSDH maintained 60% of its original activity two months after continuous use in the water–ethyl‐acetate system. Kinetic experiments showed that the increase of the apparent Km values is poor and demonstrated that the organic solvent behaves as a weak inhibitor (ki > 0.2M) for the substrate. The immobilized enzymes lyophilized in the presence of sucrose had full activity restored even after several months storage at room temperature. Immobilized hydroxysteroid dehydrogenases were shown to be suitable for preparative transformation of steroids in water–organic solvent systems.
Potentiometric method for subatrate analysis using immobilized NAD+‐dependent oxidoreductase enzymes
Authors: Chen A. K. , Liu C. C. , Schiller J. G. 
Published: December 2004

AbstractTwo coenzyme‐dependent oxidoreductases, glucose dehydrogenase and alcohol dehydrogenase, were immobilized in polyacrylamide gel over a platinum grid matrix and used as enzyme electrodes to measure their substrate concentrations in buffered aqueous solutions. The immobilized enzymes were used to oxidize their substrates in the presence of NAD+. Ferricyanide was used as the redox mediator and electroactive specific. The determinations of glucose and ethenol were utilized to demonstrate and evaluate the performance of the system. The described methodology should be readily applicable to the analysis of numerous other substrates of coenzyme‐dependent oxidoreductases.
Effects of ribonucleic acid removal methods on proteolytic activity and protein solubility in Candida utilis
Authors: Gierhart Dennis L. , Potter Norman N. 
Published: December 2004

AbstractCandida utilis was grown under controlled conditions and nucleic acids were removed from whole cells and homogenates by alkaline hydrolysis techniques, en‐zymatic methods, and washing with buffer. Homogenization released hydrolytic enzymes and proteolytic activity increased with incubation at elevated temperatures under acidic conditions. Slight proteolysis occurred in all incubated samples and this may contribute to protein insolubilization. Very little protein was lost during incu‐bation when compared to similar processes using bakers' yeast. This can be due to lower levels of protease activities in C. utilis. Alkaline hydrolysis methods resulted in hydrolysis of some proteins and irreversible insolubilization of the protein. These methods also destroyed any residual enzymatic activities. Heat denaturation studies suggest that protein insolubilization occurs at neutral pH when heat treatments equivalent to or greater than 85° C for 15 min are used. SDS‐PAGE methods were used to characterize and monitor changes in protein. Eighteen proteins and/or sub‐units were present at levels of 1% or greater. Results may help to explain changesin functional properties of sample preparations which accompany RNA removal.
Influence of substrate on the amino acid profile and macromolecular composition of a Brevibacterium species
Authors: Miller Leslie T. , Thayer D. W. 
Published: December 2004

AbstractBrevibacterium JM98A (ATCC 29895) was grown aerobically in carbon‐limited continuous culture on the following substrates: gluconic acid, galactose, fumaric acid, glutamic acid, and aspapagine. Both whole and trichloacetic acid(TCA)‐ex‐tracted cells were analyzed for their amino acid compositions. No significant variations of amino acid profile were induced by change of substrate. Only the valine content varied significantly with growth rate. Some significant variations were observed between whole and extracted cell samples, primarily in the levels of the essential amino acids threonine, cystine, and valine.
Effects of external diffusion and design geometry on the performance of immobilized glucose isomerase reactor system
Authors: Lee S. B. , Kim S. M. , Ryu Dewey D. Y. 
Published: December 2004

AbstractUsing immobilized glucose isomerase, the effects of superficial velocity of the reaction solution flowing through a packed‐bed reactor on the apparent kinetic constants of reversible reaction system were studied. The results showed that the apparent kinetic constants, both Vm″ and Km″, of the forward reaction varied significantly as the superficial velocity is changed, whereas those of the reverse reaction varied only slightly. Using the kinetic data determined experimentally, computer simulation of the enzyme reactor performance was carried out, and the importance of the external mass transfer in the proximity of immobilized‐enzyme particles was recognized. The reactor performance, expressed in terms of productivity, was examined as a function of the reactor height‐to‐diameter ratio, H/D. The productivity of the reactor system goes through a maximum value at a H/D ratio of about 1.6. and decreases as the H/D ratio increases. Theoretical analysis of the reaction kinetics of immobilized‐enzyme system that has reversible reaction kinetics is also presented. The experimental results showed good agreement with the results found from the theoretical analysis and the computer simulation studies. Based on the principles of the methods and the results presented in this paper, it is anticipated that one can predict the optimal design and operating conditions for the glucose isomerase reactor system and that application of the results could be extended to other enzyme systems with reversible reaction kinetics.
Separation of gentamicin by foaming
Authors: Lee S. B. , Ryu Dewey D. Y. 
Published: December 2004

AbstractIn order to develop a more economical separation method and to determine the feasibility of such a method for the recovery of gentamicin from fermentation broth, a foam separation process was evaluated using a batch system. The effects of such process variable as surface‐active agent, pH, collector–colligent ratio, and the gas flow rate on the separation efficiency of gentamicin were studied. Form the experimental results, the optimal operating conditions selected were: pH below 9.0, collector‐to‐colligent ratio of 3, and airflow rate at 0.5 vol air/vol liquid/min. Under these operation conditions, the average recovery efficiency of gentamicin was 73% when sodium dodecyl sylfate was used as a collector. A mathematical expression for the foam separation rate was derived. The theoretically predicted values of separation efficiencies agreed reasonably well with the experimental results.
Analysis of the coupled transport, reaction, and deactivation phenomena in the immobilized glucose oxidase and catalase system
Authors: Reuss M. , Buchholz K. 
Published: December 2004

AbstractIn a previous paper, the overall or macrokinetics of the immobilized glucose oxidase–catalase system has been presented. In this paper a detailed analysis of the interaction of diffusion and reaction in this system will be presented. The mathematical treatment includes two consecutive reactions with two‐substrate kinetics. Furthermore, the deactivation of both enzymes due to the intermediate product peroxide is taken into account. The predicted results suggest that the efficiency of the glucose oxidase reaction depends on the concentration ranges of the two substrates. Furthermore, the external mass‐transfer rate may cause a shift from glucose limitation to oxygen limitation. The efficiency of the coupled system is always higher than that predicted for the uncoupled reaction path. The calculations show that the economics of the coupled system depend a great deal on the deactivation of the enzymes.
Hydrophobic esters of cellulose: Properties and applications in biochemical technology
Authors: Dixon James , Andrews Philip , Butler Larry G. 
Published: December 2004

AbstractWe have investigated the utility for enzyme immobilization of several hydrophobic cellulose esters, as a function of solvent composition, extent of esterification, and enzyme. Phenoxyacetyl cellulose was also used for immobilization of rat liver microsomes, hydrophobic chromatography of proteins, and removal of Triton X‐100 from protein solutions. Phenoxyacetyl groups esterified to cellulose were much less subject to enzymatic hydrolysis than soluble phenoxyacetyl esters.
Temperature effects on ethanol and isopropanol utilization by Candida krusei
Authors: Kilian S. G. , Prior B. A. , Lategan P. M. , Kruger W. C. J. 
Published: December 2004

AbstractCandida Krusei has a optimum growth temperature of 37°C on SASOL ethanol‐isopropanol mixture. The organism was unable to grow on isopropanol, but oxidized it partially to acetone in the presence and absence of ethanol. Growth at 40°C in the alcohol mixture was slightly faster than at 30°C over an ethanol concentration range of 0.43 to 3.6% (v/v), although at both temperatures the growth rate declined continuously with increasing concentration. At an ethanol concentration greater than 3.6% (v/v), the mixture was much more inhibitory to growth at 40 and 30°C. The inhibitory effect was due to the ethanol rather than the isopropanol. Metabolites such as acetate, acetaldehyde, and ethyl acetate accumulated in the medium, but the degree of accumulation depended upon the temperature and alcohol mixture concentration. At 40°C, acetaldehyde and acetate accumulated to a greater extent than 30°C on a 4.0% (v/v) synthetic alcohol mixture and this may also cause the greater inhibition at this temperature. The alcohol mixture is unsuitable for single cell protein (SCP) production in batch culture because of the low cell densities observed at all alcohol concentrations.