bluuebunny/crossref_metadata_2025_split huggingface dataset:
Batch‐ and continuous‐culture studies of a methane‐utilizing mixed culture
Authors: Lamb S. C. , Garver J. C. 
Published: December 2004

AbstractA methane‐utilizing mixed culture isolated from activated sludge by selective enrichment at 45°C was found to consist of three interacting species: a methaneutilizing bacterium, a citrate‐utilizing bacterium, and a methanol‐utilizing bacterium. All three species grew well at 45°C. Three different stable mixed cultures were reconstituted by various combinations of these pure cultures. The nutritional requirements and substrate ranges for each pure culture were determined. The nutritional requirements and substrate ranges for each pure culture were determined. The saturation constant for the methane‐utilizing bacterium on methane (K) and for the methanol‐utilizing bacterium on methanol (K) were 1.73 × 10−6M and 4.51 × 10−7M, respectively. The volumetric mass transfer coefficient for methane (KLa) was determined to be 65.6 hr−1.
Production of maltose and maltotriose from starch and pullulan by a immobilized multienzyme of pullulanase and β‐amylase
Authors: Ohba Riichiro , Ueda Seinosuke 
Published: December 2004

AbstractPullulanase was immobilized on tannic acid and TEAE‐cellulose, and β‐amylase was covalently immobilized on p‐aminobenzylcellulose. Both the immobilized enzymes showed similar properties in pH and temperature optima and heat stability. On passing the pullulan solution at high temperature (50°C) through a column packed with immobilized pullulanase, only maltotriose was obtained for ten days and the half‐life was about 15 days. In a continuous reaction using immobilized multienzyme, starch was completely converted into maltose at 50°C and at a space velocity of 1.2, a comparative longer half‐life (20 days) was obtained. It was concluded that starch was smoothly converted into maltose with the aid of α‐amylase contaminated in the immobilized pullulanase and the operational stability of the column increased with 2‐5mM Ca2+.
Effects of controlled gas environments in solid‐substrate fermentations of rice
Authors: Bajracharya Rupak , Mudgett Richard E. 
Published: December 2004

AbstractThe gas environment is solid‐substrate fermentations of rice significantly affected levels of biomass and enzyme formation by a fungal species screened for high amylase production. Constant oxygen and carbon dioxide partial pressures were maintained at various levels in fermentations by Aspergillus oryzae. Control of the gas phase was maintained by a “static” aeration system admitting oxygen on demand and stripping excess carbon dioxide during fermentation. Constant water vapor pressures were also maintained by means of saturated salt solutions. High Oxygen pressures stimulated amylase productivity significantly. On the other hand, amylase production was severely inhibited at high carbon dioxide pressures. While relatively insensitive to oxygen pressure, maximum biomass productivities were obtained at an intermediate carbon dioxide pressure. High oxygen transfer rates were obtained at elevated oxygen pressures, suggesting, in view of the stimulatory effect of oxygen on amylase production, a stringent oxygen requirement for enzyme synthesis. Solid‐substrate fermentations were highly advantageous as compared with submerged cultures in similar gas environments. Not only were amylase productivities significantly higher, but the enzyme was highly concentration in the aqueous phase of the semisolid substrate particles and could be extracted in a small volume of liquid. Results of this work suggest that biomass and product formation in microbial processes may be amenable to control by the gas environment. This is believed to offer an interesting potential for optimizing selected industrial fermentation processes with respect to productivity and energy consumption.
Extracellular microbial polysaccharides: Kinetics of Pseudomonas sp., Azotobacter vinelandii, and Aureobasidium pullulans batch fermentations
Authors: Klimek J. , Ollis D. F. 
Published: December 2004

AbstractThe generality of a fermentation kinetic model (developed earlier for xanthan gum production by Xanthamonas campestris) is tested by application to several other polysaccharide‐producing fermentations. With literature batch data for exopolysac‐charides from Azotobacter vinelandii, Pseudomonas sp., and Aureobasidium pullulans, the model is shown to provide a reasonable description for biomass (X), product (polysaccharide, P), and substrate (S) evolution in time. Thus a general kinetic model for microbial fermentations that produce exopolysaccharides is established.
A macroscopic model describing yield and maintenance relationships in aerobic fermentation processes
Authors: Heijnen J. J. , Roels J. A. 
Published: December 2004

AbstractThe present paper presents a generalized treatment of the principles of elemental and enthalpy balances which are applied to aerobic fermentation processes. It is shown that strict relations do exist between the various yield factors of biomass or product on substrate, oxygen, carbon dioxide, and between the various maintenance coefficients. These relations are confirmed from the existing body of literature data on yield and maintenance coefficients. Another consequences of the application of elemental balances is the existence of limits for the maximum biomass yield on substrate and oxygen, which depend on the degree of reduction of the substrates with different degree of reduction. It appears from this model that substrates with a high degree of reduction are C limited and substrates with a low degree of reduction are energy limited. Finally the effects of temperature on yield and maintenance coefficients are analyzed from the existing body of literature data. It can be concluded that the maintenance coefficients follow an Arrhenius type of relationship and that yield is temperature independent. The literature data seem to indicate that a degree of reduction of about 4 is optimal for the carbon and energy needs for biomass formation.
Disruption of Candida utilis cells in high pressure flow devices*
Authors: Engler Cady R. , Robinson Campebell W. 
Published: December 2004

AbstractThe disruption of Candida utilis cells in suspensions subjected to different types of stress was investigated. Stresses caused by impingement of a high velocity jet of suspended cells against a stationary surface were found to be significantly more effective for disruption than either shear or normal stresses. The fraction of cells disrupted by impingement is a first order function of the number of passes through the disruptor and, over a prescribed range of operating pressures, is a power function of pressure. These results indicate that impingement is the predominant mechanism causing cells disruption in high pressure flow devices such as Manton–Gaulin homogenizers. The impingement results suggest that cells grown in cyclic batch culture are easier to disrupt than cells grown at a lower specific growth rate in continuous culture. In addition to determining the fraction of cells disrupted, the release of invertase activity was determined for the impingement experiments. The fraction of total invertase activity released was found to be somewhat greater than the fraction of cells disrupted.
The effect of combined chemical and enzyme treatments on the saccharification and in vitro digestion rate of wheat straw
Authors: Ben‐Ghedalia Daniel , Miron Joshua 
Published: December 2004

AbstractWheat straw was pretreated with sodium hydroxide, ozone, and sulfur dioxide, and subsequently treated with four sources of cellulase, T. reesei, T. reesei, T. viride, A. niger, and Oxyporus sp. The effect of the combined chemical + enzyme treatments on the extent of saccharification and on the digestion rate by rumen microorganisms was studied. Cellulases were applied at an equal but low concentration (0.5 FPU/ml) on the pretreated straw. The combined treatments, SO2 + T. reesei cellulase nd SO2 + T. viride cellulase, produced the highest and significant levels of reducing sugars (RS), 577 and 597 mg RS/g straw organic matter. The highest enzyme efficiency, 44.7 mg RS/mg enzyme, was found with T. reesei cellulase when applied on SO2 pretreated straw. The in vitro organic matter digestibility was affected significantly only by the chemical pretreatments, whereas the effect of the cellulases was expressed mainly in increasing the fermentability of the hydrolyzed straw. The in vitro digestion pattern of the saccharified straw was found to be typical of a highly fermentable feed and comparable to a starchy mixture such as used in concentrate ruminant diets.
Cultivation of a filamentous mold in a glass pilot‐scale airlift fermentor
Authors: Malfait J. L. , Wilcox D. J. , Mercer D. G. , Barker L. D. 
Published: December 2004

AbstractResults of pilot plant studies using a glass airlift fermentation device (55 liter fermentation volume) have proven the relative merits of such a system in the fermentation of a filamentous mold, Monascus purpureus, on 4% (w/w) starch media. The resultant overall yield of cell mass (Yx/s) of 0.38 was an appreciable increase over the 0.32 obtained with a pilot scale stirred tank fermentor previously studied. Power requirements of the airlift fermentor were approximately 50% of those for the mechanically agitated system. The lack of mechanical shear in the airlift system provides a more gentle environment or the cultivation of organisms than does the high degree of shear prevalent in the mechanically agitated vessels. Mass transfer of oxygen to the aqueous phase of the fermentation volume is improved significantly through use of the airlift device. Mass transfer coefficients in the range of 200 reciprocal hr were obtained to approximately 80 reciprocal hr in the stirred tank fermentor.
Experimental evaluation of a quasi‐steady‐state controller for yeast fermentation
Authors: Kalogerakis N. , Boyle T. J. 
Published: December 2004

AbstractThe quasi‐steady‐state (QSS )controller whose implementation on a computer‐coupled laboratory fermentor was presented earlier is briefly reviewed. The slow rate of approach to QSS of the uncontrolled process is verified experimentally. The ability of the control system to rapidly force the system to QSS is demonstrated by a run in which three different QSS points are achieved in a single 12 hr fermentation. The nonlinear nature of the process and the ability of the control system to handle this is demonstrated by comparing the response times to command inputs of different sizes. Noninteraction between cell and substrate response modes is demonstrated. The ability of the system to manipulate substrate concentration in the vessel without a direct measure of it is shown.
Multiple steady‐state phenomena within enzyme reactors: The enzyme reaction with two substrates
Authors: Webster Ian A. , Shuler Michael L. 
Published: December 2004

AbstractThe theoretical dynamic characteristics of an isothermal continuous flow stirred tank enzyme reactor (CFSTER) operating on two substrates are investigated. Under certain conditions multiple steady states are possible; namely, with an enzyme which binds with the two substrates sequentially. The occurrence of multiple steady states is found to be primarily dictated by three dimensionless parameters which incorporate rate law constants. The global stability of certain steady states is examined by numerically solving the transient material balance on the CFSTER. The effect of recycle on the dynamics of an isothermal plug flow enzyme reactor (PFER) is also studied. A general conclusion indicated by this work is that any open isothermal reaction system wherein the reaction rate law passes through a maximum with increasing substrate concentration and where back mixing occurs with exhibit multiple steady‐state behavior in some operating range.
Yeast alcohol dehydrogenase immobilized in a glutaraldehyde–albumin matrix: Kinetics and cofactor diffusional effects*
Authors: Millis James R. , Wingard Lemuel B. 
Published: December 2004

AbstractThis study was carried out to define how the overall rate of reaction would be influenced by different degrees of diffusional resistance to cofactor transport within an oxidoreductase membrane matrix. To accomplish this, 0.7–6.6μMyeast alcohol dehydrogenase was immobilized in an albumin matrix crosslinked with 2.5 or 5.0% glutaraldehyde to give 102–1685 μM thick membranes. The enzyme half‐life was at least doubled at pH 7.5 or 8.8 on immobilization. Values of the kinetic constants for the soluble and immobilized enzyme were determined at 25°C and pH 8.8 over the range of 0.01–1.0Mbulk solution concentration of ethanol as substrate and 140–1000μMbulk solution concentration of nicotinamide adenine dinucleotide (NAD+) as cofactor, to give essentially single substrate kinetics in NAD+. Equilibrium partitioning of ethanol and NAD+between the solution and membrane was measured and used in the data analysis. The four kinetic constants for the soluble enzyme agreed with literature values; and all increased with immobilization of the enzyme. The Michaelis constants for NAD+and for ethanol were greater for the immobilized enzyme. The diffusional resistance to NAD+transport, presented in terms of the Thiele modulus, showed that the overall rate of reaction was decreased by about 50% even at values of the modulus as low as 2.0.
The isolation of lytic enzymes from Cytophaga and their application to the rupture of yeast cells
Authors: Asenjo J. A. , Dunnill P. 
Published: December 2004

AbstractYeast–lytic enzymes have been isolated on a pilot scale from Cytophaga species by precipitation and the light, enzyme‐rich solid phase recovered by liquid‐liquid separation. The enzyme complex was immobilized to soluble polymeric carbohydrates and the effectiveness of the free and immobilized enzyme for protein release and cell debris dissolution has been assessed.
Stabilization of phosphorylating mitochondrial electron transport practicles and their use for ATP regeneration
Authors: Matsuoka Hideaki , Suzuki Shuichi , Aizawa Masuo 
Published: December 2004

AbstractA possible use of phosphorylating mitochondrial electron transport particles (ETPH) has been investigated for ATP regeneration. The oxidative phosphorylation of ETPH was considerably inhibited by the hydrolytic activity of ATPase and adenylate kinase. The hydrolytic activity of ATPase and adenylate kinase were found to be intensively retarded in the presence of Mg2+. ETPH continuously regenerated ATP from ADP over 4 hr when suspended in an isotonic buffer containing ADP, succinate, and 100 mM MgSO4. Furthermore, repeated use of ETPH was possible for ATP regeneration primarily due to considerable stabilization of the electron transport system.
Interrelationship among specific rates of cell growth, substrate consumption, and metabolite formation in some simple microbial reactions producing primary metabolites
Authors: Yamané Tsuneo , Shiotani Takeshi 
Published: December 2004

AbstractApplying the carbon balance principle, the interrelationship between ν = μ/Y + m (μ is the specific growth rate of microorganism, v is the specific substrate consumption rate) and π = Aμ B (Luedeking–Piret eqyuation, π is the specific metabolite formation rate) has been established for three types of simple microbial reactions. Equations for the kinetic parameters A and B have been proposed for each of the three types of microbial reactions, Expresses in terms of γx, γs and γp (carbon contents of dry cell, mass, major carbon energy source, and metabolite) as well as the parameters Y and m. Values of both A and B calculated from the proposed equations were compared with their experimental data for lactic acid fragmentation, aerobic SCP production, and alcohol fermentation. The estimated values agreed with the observed ones with reasonably small deviations.
Alcohol production from jerusalem artichoke using yeast with inulinase activity
Authors: Guiraud J. P. , Daurelles J. , Galzy P. 
Published: December 2004

AbstractThe obtaining of a fermentable extract from Jerusalem artichoke is simple. Yeasts with inulinase activity can be used to produce ethanol with good profitability. This method makes it possible to obtain 25 to 65 hl ethanol/ha with by‐products usable as feed.
Use of glucose oxidase system in measuring aeration capacity of fermentors. Comparison of the dynamic and steady‐state methods of kla measurement
Authors: Linek V. , Beneš P. , Hovorka F. , Holeček O. 
Published: December 2004

AbstractA steady‐state method for kla determination has been presented using the Michaelis–Menten two‐substrate kinetic equation for oxidation of glucose in the presence of the enzymes glucose oxidase and excess catalase. The conditions have been specified where spontaneous hydrolysis of lactone is sufficiently rapid, thus eliminating inhibitory action of lactone on the oxidation. In glucose oxidase‐free batches, the kla values were determined using various modification of the dynamic method. The dynamic methods in which gas interchange was effected without interrupting aeration and agitation of the batch yielded erroneously lower kla values as compared to the results of steady‐state methods if the measured kla value was higher than 0.03 s−1. The values yielded by the dynamic method in which the gas interchange was effected at the same time with turning on aeration and agitation of the batch agreed with values resulting from the steady‐state method provided that the measured kla values were lower than 0.08−1 and the simultaneous interfacial transport of nitrogen and oxygen had been taken into account in the evaluation. At kla values higher than 0.08 −1, this modification of the dynamic method also yielded lower kla values as compared with the outcome of the steady‐state method. The experiments performed do not, however, allow one to decide unambiguously on the whether these lower kla values are due to failure of the adopted model to describe adequately the dynamic behavior of the system or whether they are true values differing from those yielded by the steady‐state method on account of different physical properties of compared batches.
A mathematical model for the aerobic growth of Saccharomyces cerevisiae with a saturated respiratory capacity
Authors: Barford J. P. , Hall R. J. 
Published: December 2004

AbstractA mathematical model for the aerobic growth of Saccharomyces cerevisiae in both batch and continuous culture is described. It was based on the experimental observation that the respiratory capacity of organism may become saturated and exhibit a maximum specific oxygen uptake rate after suitable adaptation. This experimental observation led to the possibility that transport into and out of the mitochondrion was of major importance in the overall metabolism of S. cerevisiae and was subject to long‐term adaptation. Consistent with this observation a distributed model was proposed which. as its basis, assumed the control of repression or inhibition of the uptake rates of other substrates. No other regulation of fermentation and respiration was assumed. The model provided a suitable structure allowing precise quantification of the changes in rate and stoichiometry of energy production. The model clearly indicated that growth under the wide range of experimental conditions reported could not be predicted using constant values for the maximum specific respiratory rate of constant values of YATP (g biomass/mol ATP) and PO ratio of (mol ATP/atom oxygen). The causes of the variation in the respiratory rate were not determined and it was concluded that a more detailed analysis (reported subsequently) was required. The variation of YATP and PO ratio with specific growth rate implied that the efficiency of ATP generation or ATP utilization decreased with increasing specific growth rate. It was concluded that it was not possible to quantify the individual effect of YATP and PO ratio until independent means for their reliable estimation is available.
Optimization of batch alcoholic fermentation of glucose syrup substrate
Authors: Chen S. L. 
Published: December 2004

AbstractThe quantitative effects of substrate concentration, yeast concentration, and nutrient supplementation on ethanol content, fermentation time, and ethanol productivity were investigated in a Box–Wilson central composite design experiment, consisting of five levels of each variable, High substrate concentration, up to 30° Brix, resulted in higher ethanol content (i.e., up to 15.7% w/v or 19.6% v/v) but longer fermentation time and hence lower ethanol productivity. Increasing yeast concentration, on the other hand, resulted in shorter fermentation time and higher productivity. The highest ethanol productivity of about 21 g EiOH/L h was obtained at low substrate concentration (i.e., 12° Brix), low alcohol content (i.e., 6% by weight), high yeast concentration (i.e., 4.4%), and high supplementation of yeast extract (i.e., 2.8). Productivity of this magnitude is substantially higher that that of the traditional batch fermentation of fed‐batch fermentation. It is comparable to the results of continuous fermentation but lower than those of vacuum fermentation but lower than those of vacuum fermentation. Optimal conditions for maximal ethanol productivity can be established by a multiple regression analysis technique and by plotting the contours of constant response to conform to the constraints of individual operations.
On the production of dextran by free and immobilized dextransucrase
Authors: Monsan P. , Lopez A. 
Published: December 2004

AbstractDextransucrase from Leuconostoc mesenteroides was produced in a semicontinuous culture with slow addition of a concentrated sucrose solution. The resulting high activity of the fermentation broth allowed a one‐step purification method, by gel permeation chromatography (GPC) in 96.4% yield. This procedure resulted in 140‐fold purification, with specific activity of 122 U/mg. The enzyme was immobilized onto an amino‐Spherosil support activated with glutaraldehyde. Preparations with dextransucrase activities as high as 40.5 U/g of support were obtained, when low specific area supports were used and maltose was added during the enzyme coupling. Diffusional limitations were found during enzyme reaction, as shown by a kinetic study. As a consequence of immobilization, the average molecular weight of dextrans seems to increase. Immobilized dextransucrase looks promising for low‐molecular‐weight dextran production. Clinical dextran was synthesized when the polysaccharides produced in the presence of maltose were used as acceptor of a second synthesis reaction. The molecular weight distribution of the resulting production was less disperse than when clinical dextran was produced by acid hydrolysis of high‐molecular‐weight dextran.
Kinetics of phenol oxidation by washed cells
Authors: Sokol W. , Howell J. A. 
Published: December 2004

AbstractThe uptake of phenol by pure cultures of Pseudomonas putida growing on phenol in continuous culture has been studied. The purpose of the experiments was to determine the kinetic parameters governing uptake of phenol by organisms growing on phenol in the high‐conversion range by measuring uptake rates per unit biomass per unit time at various phenol concentrations. The microorganisms used were taken from a chemostat at residence times of 8, 5.25, 3.85, 3.2, 3, and 2.7h. The Monod–Haldane model and modifications of it were applied to the data and the best kinetic parameters were determined by nonlinear least‐squares techniques. The best model was a two‐parameters simplification of Monod–Haldane in which μ = K1S/(K2 + S2). The value of K1 was found to increase monotonically with the value of phenol concentration in the original chemostat with an apparent induction “threshold” of 0.1 mg/L.