bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling and static optimization of the ethanol production in a cascade reactor. I. Modeling
Authors: Dourado A. , Goma G. , Albuquerque U. , Sevely Y. 
Published: December 2004

AbstractLet us consider the modeling of a cascade reactor for the production of ethanol. The rates of reaction in alcoholic fermentation are modeled so that it can assume both ethanol and substrate inhibition, in relation to the observed results.A nonstructured model, based on biomass, substrate, and ethanol concentrations, is developed and identified. It is a complex model, this being due to the nonlinearity between the specific rate of ethanol production and the growth rate and, on the other hand, the study of the static optimization of ethanol fermentation is performed.
Generalization of monod kinetics for analysis of growth data with substrate inhibition
Authors: Luong J. H. T. 
Published: December 2004

AbstractThe inhibitory effect of butanol on yeast growth has been studied for the strain Candida utilis ATCC 8205 growing aerobically on butanol under batch conditions. A mathematical expression was then proposed to fit the kinetic pattern of butanol inhibition on the specific growth rate:

The maximum allowable butanol concentration above which cells do not grow was predicted to be 9.16g/L. The proposed model appears to accurately represent the experimental data obtained in this study and the literature data developed for a variety of batch culture systems at widely ranging substrate concentrations.
Simulations of host–plasmid interactions in Escherichia coli: Copy number, promoter strength, and ribosome binding site strength effects on metabolic activity and plasmid gene expression
Authors: Peretti Steven W. , Bailey James E. 
Published: December 2004

AbstractA mechanistically detailed single‐cell model E. coli B/r‐A was adapted to simulate the effects of vector presence on cell metabolism. Competition for RNA polymerase between chromosome and plasmid DNA is explicitly included. Distribution of active ribosomes among chromosome‐ and plasmid‐derived messenger RNA, another key facet of host–plasmid interactions, is also treated in detail. Simulations of recombinant cell growth rate and cloned‐gene productivity as a function of relative plasmid number per cell agree closely with experimental results. Model prediction of the variation of cell cycle parameters C and D with plasmid number are roughly consistent with available data. Models of this class can be used to simulate changes in productivity resulting from specific alterations in the expression vector. The effects of changing cloned‐gene promoter and ribosome binding strengths and of augmenting cell transcription or translation capacity have been studied using the recombinant cell model. Results suggest that cloned‐gene expression is limited by cellular transcription capacity. These and other parametric studies, conveniently implemented using the computer cell, provide important guidance for future experiments directed at better understanding of host–plasmid interactions and at optimizing recombinant system productivity.
The dehydration of fermentative 2,3‐butanediol into methyl ethyl ketone
Authors: Tran Ai V. , Chambers Robert P. 
Published: December 2004

AbstractA solid acid catalyst consisted of sulfonic groups covalently bound to an inorganic matrice was developed to dehydrate 2,3‐butanediol into methyl ethyl ketone. Rate constant and apparent activation energy of the dehydration reaction were determined. The decay course of the catalyst was a two‐stage curve. The catalyst was deactivated more rapidly in the first stage than in the second stage. The strategy of maintaining constant degree of dehydration was employed to lengthen the lifetime of catalyst. Treatment of the 2,3‐butanediol containing fermentation broth with activated carbon greatly facilitated the subsequent dehydration reaction.
Theoretical and experimental yields for photoautotrophic, mixotrophic, and photoheterotrophic growth
Authors: Lee H. Y. , Erickson L. E. 
Published: December 2004

AbstractAvailable electron methods are presented and used to estimate theoretical energetic growth yields for photoautotrophic, mixotrophic, and photoheterotrophic growth of algae and photosynthetic bacteria. The theoretical yields are compared to experimental values reported previously. For photoautotrophic and mixotrophic growth of algae experimental values that approach and even exceed the theoretical values have been reported in the literature. For photosynthetic bacteria experimental yields are much smaller than thetheoretical maximum values.
Kinetics of milk coagulation: II. Kinetics of the secondary phase: Micelle flocculation
Authors: Carlson Alfred , Hill Charles G. , Olson Norman F. 
Published: December 2004

AbstractA kinetic model for the agglomeration of milk micelles following κ‐casein hydrolysis is described. The key features of the model are: (1) the surface potential of casein micelles is sufficient to explain the colloidal stability of the milk system; (2) the reduction in surface potential following κ‐casein hydrolysis explains the loss of stability; (3) partial hydrolysis leads to limited agglomeration; and (4) the kinetics of agglomeration are compatible with the theory that completely hydrolyzed micelles have only a limited number of interaction sites. The model accurately predicts solution turbidity increase assuming that micelles have only circa 1.2 interaction sites on the average under the experimental conditions of this study.
The kinetics of milk coagulation: IV. The kinetics of the gel‐firming process
Authors: Carlson Alfred , Hill Charles G. , Olson Norman F. 
Published: December 2004

AbstractA mechanistic kinetic model of gel firmness development during milk gel formation is presented. The model correctly accounts for the influence of enzymatic κ‐casein hydrolysis on the rate of firmness development in renneted milk gels. The model used is based on two first‐order reactions occurring in series. The first reaction is enzymatically controlled and corresponds to the formation of gel crosslink sites by κ‐casein hydrolysis. The second reaction is nonenzymatic and corresponds to the process of crosslink formation and depletion of active sites. The model successfully predicts gel firmness development in the temperature range 31–45°C for a variety of initial enzyme concentrations.
Growth inhibitory and lethal effects of ethanol on Escherichia coli
Authors: Sawada Tatsuro , Nakamura Yoshitoshi 
Published: December 2004

AbstractThe growth inhibitory and lethal effects of ethanol on Escherichia coli BB were investigated in batch cultures, by measuring total cell number, viable cell number, and cell mass concentration. Ethanol below ca. 50 g/L allowed exponential growth but depressed the specific growth rate. The effect of ethanol on the specific growth rate appeared to follow noncompetitive inhibition kinetics with apparently cooperative binding with a Hill coefficient of 2.5. The Hill coefficient and the inhibition constant were temperature independent over the range tested. Ethanol at 30 g/L decreased the growth yield. Ethanol enhanced the specific death rate in an experimental way. Stationary cell populations were more resistant than exponential ones but the degree of enhancement by ethanol was the same in both populations. Isopropanol and propanol also enhanced the specific death rate exponentially and the degree of enhancement was correlatedwith their membrane–buffer partition coefficients.
Preparation and properties of soluble–insoluble immobilized proteases
Authors: Fujimura Motoki , Mori Takao , Tosa Tetsuya 
Published: December 2004

AbstractIn order to carry out an effective enzyme reaction, the preparation of soluble–insoluble immobilized enzyme was investigated. Proteases were selected as model enzymes, and their immobilization was carried out by using an enteric coating polymer as a carrier. Among the polymers tested, methacrylic acid–methylacrylate–methylmethacrylate copolymer (MPM‐06) gave the most active soluble–insoluble immobilized papain. This immobilized papain showed insoluble from below pH 4.8 and soluble form above pH 5.8; it was also soluble in water‐miscible organic solvent. It was reusable and more stable with heat and water‐miscible organic solvents than native proteases. Furthermore, various proteases could be immobilized by using MPM‐06 with high activity. Chymotrypsin immobilized by this method catalyzed the effective peptide synthesis in a heterogeneous reaction system containing water‐miscible organic solvent.
Isolation of a respiratory‐deficient Kluyveromyces fragilis mutant for the production of ethanol from Jerusalem artichoke
Authors: Guiraud Joseph P. , Bourgi Jamal , Stervinou Michèle , Claisse Maurice , Galzy Pierre 
Published: December 2004

AbstractA respiratory‐deficient, mutant of Kluyveromyces fragilis was isolated using a ethidium bromide mutagenesis. It was characterized by a loss of cytochromes a + a3 and by an improvement of its inulinase activity. Under anaerobic conditions this mutant was always better than the wild strain for ethanol production especially from Jerusalem artichoke extracts containing large amounts of high polyfructosans ("early" extracts).
Properties and quality characteristics of rennin extracted by ultrasound
Authors: Zayas Joseph F. 
Published: December 2004

AbstractAn optimal time of 45 min was established for extraction of rennin (chymosin) from abomasa using ultrasound. Effect of swelling of raw material and increased temperature of extraction medium (45°C) was established. As rennin is resistant to ultrasound treatment and enhanced temperatures, ultrasound extraction results in a significant increase in the yield and activity. However, purified rennins were sensitive to ultrasound action. There were found changes of the electrophoretic properties and amino acid composition. Physicochemical properties were different and quality characteristics were higher for ultrasonic extracted rennin than for the control, particularly specific clotting activity, proteolytic activity, and rheological properties of curd. However, nonspecific proteolysis, coefficient of rennin effectivity, appearance, odor, solubility, moisture, protein, and NaCI content were similar. Ultrasonic extraction caused a decrease in the total viable counts of microorganisms of rennin, because of the short time of extraction.
Invertase activity of intact cells of Saccharomyces cerevisiae growing on sugarcane molasses. II. Unsteady‐state continuous‐culture tests
Authors: Vitolo Michele , Vairo Marina L. R. , Borzani Walter 
Published: December 2004

AbstractDuring unsteady‐state continuous culture of Saccharomyces cerevisiae on sugarcane blackstrap molasses, the invertase activity of the intact yeast cells oscillated. Disturbances were produced by changing medium composition, air rate, impeller speed, and dilution rate. The influence of the oxygen supply rate and of the dilution rate on the invertase activity depend on the medium composition. The highest invertase activity was obtained when, after a steady‐state attained using unsupplemented culture medium, nutrients were added to the feeding mash. A Monod‐like equation seems to be the best representation of the correlation between the specific rate of reducing sugars consumption and the specific rate of nonreducing sugar hydrolysis by the yeast cells.
Modelling mass transfer and agitator performance in multiturbine fermentors
Authors: Bader Fredric G. 
Published: December 2004

AbstractA methodology for mathematically analyzing agitator performance and mass transfer in large multiturbine production fermentors is presented. The application of this approach provides a method for determining axial dissolved oxygen profiles under conditions of known mass transfer rates as a function of agitation–aeration characteristics. A stagewise approach is used which divides the fermentor into a series of mixing cells. This allows for each turbine and mixing cell to be individually optimized. The model also permits the determination of the mass transfer coefficient for each turbine based upon limited dissolved oxygen data. The primary limitation of this approach rests in the limited data and correlations available for multiturbine systems. The structure of the modelling approach can serve as a basis for testing single turbine correlations and adapting them to multiturbine systems. The step‐by‐step details of the mathematical analysis are presented and interpreted. A series of computer simulations demonstrate the effect of typical fermentor operating variables on the axial dissolved oxygen profile. Further simulations demonstrate the effect of modifying agitator blade numbers on the dissolved oxygen profile and agitator power requirement.
Acidogenic fermentation of lactose
Authors: Kisaalita W. S. , Pinder K. L. , Lo K. V. 
Published: December 2004

AbstractCheese whey is the main component of waste streams from cheese manufacturing plants. Whey is a high biochemical oxygen demand (BOD) effluent that must be reduced before the streams are sent to the sewer. It is proposed in this article that the production of methane by anaerobic fermentation would be the best use of this stream, especially for small plants. Single‐stage fermentation of lactose, the main component of whey, results in a very low pH and a stalled process. Two‐phase fermentation will eliminate this problem. The acidogenic stage of fermentation has been studied at pH of between 4 and 6.5. The nature of the main products of the reaction have been found to be pH dependent. Below a pH of 4.5 a gas (CO2 and H2) is produced along with ethanol, acetate, and butyrate. Above a pH of 4.5 no gas was produced, and the liquid products included less ethanol and butyrate and more acetate. A separate study on the conditions for gas formation showed that if the pH dropped for a short time below 4.5 gases were formed at all subsequent pH. This would indicate a change in population distribution due to the period at a low pH. By assuming that the desired products from the acidogenic stage were butyrate, acetate, and no gases, the optimum pH range was found to be between 6.0 and 6.5.
The use of rotifers for the maintenance of monoalgal mass cultures of Spirulina
Authors: Mitchell S. A. , Richmond A. 
Published: December 2004

AbstractZooplankton was successfully used for the biological control of unicellular algal contaminants in Spirulina mass cultures even under conditions adverse to the growth of Spirulina (maximal winter daily temperature of approximately 10°C and very low bicarbonate concentration). Brachionus plicatilis (Rotifera) was the most successful species of zooplankton used. The interrelationships between Spirulina, green unicellular contaminant, and B. plicatilis were studied under various conditions. Two species of unicellular contaminant were used; Monoraphidium minutum was isolated from local cultures and Chlorella vulgaris, obtained from contaminated Spirulina cultures in Israel. The rotifer B. plicatilis successfully controlled the population size of both contaminants whether they were introduced in a single addition or as a daily dose. The biological control of the unicellular contaminants allows Spirulina to be cultured in a medium low in bicarbonate, thereby reducing the cost of the medium and increasing the quantity of CO2 that may be freely absorbed from the atmosphere at the optimal pH for Spirulina cultivation.
Studies on a wild strain of Schizophyllum commune: Cellulase and xylanase production and formation of the extracellular polysaccharide Schizophyllan
Authors: Steiner W. , Lafferty R. M. , Gomes I. , Esterbauer H. 
Published: December 2004

AbstractA wild strain of schizophyllum commune (Fr:Fr:) isolated in Bangladesh produced cellulase and xyianase in high yields as well as the exobiopolymer schizophyllan. It was found experimentally that concentrations of 4% Avicel, 3.5% peptone, and 0.5% Ca(NO3)2·4H2O were optimal for growth and product formation. Bacto‐peptone was found to be the most suitable substrate of a number of casein, mycological, and meat peptone preparations for enzyme production. Young plate‐culture inocula (4 days) were found to be better than comparatively aged fungal cultures (14 days). With the optimized medium, 5 units filter paper (FP) cellulase, 1244 units xylanase, 108 units β‐glucosidase, and 65 units of carboxymethyl (CM) cellulase per mL culture filtrate were obtained in shake flasks. In a laboratory fermentor the respective enzyme activities were 4.5 units FP‐cellulase, 1200 units xylanase, 100 units β‐glucosidase, and 60 units CM‐cellulase per mL culture filtrate. A biopolymer, reported to be active against can cerous cells, was an additional product in addition to the enzymes.
Unsteady‐state operation of continuous fermentor for enhancement of cell mass production
Authors: Hong Juan , Lee C. K. 
Published: December 2004

AbstractThe transient behavior of continuous fermentation is studied concentrating on the time scale intrinsic to the system. The time scale is the time required for the fermentorto reach a stable steady state after the disturbance of cell mass is introduced. When the cell concentration is disturbed from the steady‐state value, in particular, at the dilution rate near washout, the transient period becomes extended significantly, and the steady state is resumed sluggishly. This sluggish transient behavior could be turned to an advantage for enhancing the cell mass output rate. The proposed transient operation is a continuous fermentation whereby a positive disturbance in the cell mass is introduced, so that the cell concentration is higher than the steady‐state value for an extended transient period. It is shown that a significantly higher cell mass production than that from the steady‐state continuous fermentation can be achieved. Simple experiments were performed to demonstrate the improvement of cell (Candida utilis) productivity.
Immobilization of microorganisms by adhesion: Interplay of electrostatic and nonelectrostatic interactions
Authors: Mozes N. , Marchal F. , Hermesse M. P. , Van Haecht J. L. , Reuliaux L. , Leonard A. J. , Rouxhet P. G. 
Published: December 2004

AbstractThe adhesion of three microorganisms (Saccharomyces cerevisiae, Acetobacter aceti, and Moniliella pollinis) to different materials has been studied using various supports (glass, metals, plastics), some of which were treated by an Fe(III) solution. The surface properties of the cells were characterized by the zeta potential and an index of hydrophobicity; characterization of the supports involved surface chemical analysis (XPS) and contact angle measurements. Cell suspensions in pure water at a given pH were left to settle on plates; the latter were then rinsed and examined microscopically, Saccharomyces cerevisiae and A. aceti adhere to metals under certain pH conditions but do not adhere to any of the other materials tested unless it is previously treated by ferric ions; adhesion of these hydrophilic cells is essentially controlled by electrostatic interactions. Moniliella pollinis adhere spontaneously to glass and to polymeric materials, but its attachment is also influenced by cell–cell or cell–support electrostatic repulsions; near the cell isoelectric point, cell flocculation is competing with adhesion to a support.
Enzyme‐Entrapping behaviors in alginate fibers and their papers
Authors: Kobayashi Yoshinari , Matsuo Ryûkichi , Ohya Takaichi , Yokoi Nobumasa 
Published: December 2004

AbstractEnzyme immobilization in the form of fiber and paper was easily achieved by wet spinning of aqueous admixture of sodium alginate and enzymes into divalent metallic ion solution as a coagulating bath, followed by paper making of resultant shortly cut fibers. Entrapment yields of enzymes used, e.g., glucoamylase, cyclodextrin glucanotransferase, endo‐polygalacturonase, and protease, were always higher in calcium alginate fibers and their papers than those in corresponding beads. It was found that the yields increased with an increase of the discharge rate through the spinning nozzle because the higher discharge rate could provide more highly oriented metal‐chelate linear polymer molecules along the fiber axis for preventing leakage of entrapped enzymes. Divalent metallic ions affected greatly the entrapment of glucoamylase in alginate fibers, the order of which followed roughly the ionotropic series of Thiele. Entrapment of glucoamylase in bicomponent systems comprising alginate and other water‐soluble polymers was also investigated.
Species selection in a reactor–settler system
Authors: Sheintuch Moshe 
Published: December 2004

AbstractThe competition between flocculating and nonflocculating microorganisms was investigated in a continuous reactor‐settler system (e.g. activated sludge). Co existence states were found to be possible, over a certain domain of operating conditions, even with simple monotonic kinetics and simple competition. Multiple solutions exist when coexistence states are unstable. Coexistence solutions are stable when the flocculating bacteria grow faster at feed conditions as in the activated sludge problem. The analysis applies to one or several mixed or plug flow reactors. Other effects, such as enrichment of the recycle stream by the flocculating microorganism or substrate adsorption and storage, may change the structure of solution.
Kinetic study and mathematical modeling of methanogenesis of acetate using pure cultures of methanogens
Authors: Yang S. T. , Okos M. R. 
Published: December 2004

AbstractKinetics of methanogenesis from acetate was studied using pure cultures of Methanosarcina barkeri and Methanosarcina mazei. Methane formation was found to be associated with cell growth. Nearly equimolar methane was produced from acetate during the methanogenic growth, and about 1.94 g of cells were formed from each mole of acetate consumed. Cell growth can be estimated from methane production. Significant substrate inhibition was found when acetate concentration was higher than 0.12 M. Among the three methanogenic strains studied, M. mazei strain S6 had the highest specific growth rate at all acetate concentrations studied and was least sensitive to environmental factors investigated (e.g., acetate concentration). The maximum specific growth rate found for strain S6 was 0.022 hr−1 at acetic acid concentration around 7 g/L. The other two strains studied were M. barkeri strain 227 and strain MS. Growth of M. barkeri was completely inhibited at sodium acetate concentrations higher than 0.24 M. The maximum specific growth rate found for strains 227 and MS was 0.019 and 0.021 h−1 at acetic acid concentrations of 3.6 and 6.8 g/L, respectively. A kinetic model with substrate inhibition was developed and can be used to simulate the methane formation from M. mazei strain S6 grown on acetate at 35°C, pH 7.
Substrate protection of immobilized glucose isomerase
Authors: Chen Kuo‐Cheng , Wu Juan‐Yih 
Published: December 2004

AbstractUsing commercial immobilized glucose isomerase (SWETASE®, Nagase Co.), the effect of substrate protection on enzyme deactivation has been studied in a batch manner. The data analysis was carried out based on Briggs‐Haldane kinetics in which enzyme deactivation accompanying the protection of substrates was also considered. The protection factor was proposed to elucidate the dependence of the degree of substrate protection. The existence of the protection of glucose isomerase by the substrates has been verified experimentally. Also, the enzyme‐substrate complex deactivates with a decay constant which is one‐half that of the free enzyme. Theoretical analysis of enzyme deactivation with substrate protection offers an effective understanding which is essential for enzyme replacement and process optimization.