bluuebunny/crossref_metadata_2025 huggingface dataset:
Infectivity and mode of action of Baculoviruses
Authors: Granados Robert R.
Published: December 2004

The genus Baculovirus contains three subgroups of viral types: (1) nuclear polyhedrosis viruses (NPVs), (2) granulosis viruses (GVs), and (3) nonoccluded baculoviruses. While little information is available for viruses from the third subgroup, several aspects of the infectivity and mode of action of NPVs and GVs have been studied. The most common route of entry of a virus into an insect host is per os, and both virus types enter midgut cells (primary site of infection) by membrane fusion. However, two distinct mechanisms of virus uncoating occur among the baculoviruses: NPVs uncoat within the nucleus, whereas GVs uncoat at the nuclear pore complex. Baculoviruses of subgroup 3 appear to uncoat by either mechanism. In addition to replicating within the nucleus, NPV inoculum virus may pass through the intestinal epithelium immediately after ingestion, thereby establishing a systemic infection of the hemocoel prior to virus replication in midgut cells. The GVs do not appear to pass through midgut cells as rapidly as NPVs and in general, the developmental cycle of GVs is longer than that of NPVs. NPVs have been grown in cell culture while GVs have not.
Energy requirements and process design considerations in compression‐milling pretreatment of cellulosic wastes for enzymatic hydrolysis
Authors: Tassinari Thomas , Macy Charles , Spano Leo , Ryu Dewey D. Y.
Published: December 2004

The effectiveness of compression‐milling pretreatment of lignocellulosics for enzymatic hydrolysis has been demonstrated for a wide variety of substrate sources. Reductions in the degree of crystallinity and the degree of polymerization of cellulose and partial destruction of the structural integrity of lignocellulosics brought about by compression milling significantly increase the susceptibility of cellulose to enzymatic hydrolysis. The enzymatic hydrolysis yield was found to be directly related to the specific energy input to the cellulosic substrate (kWh/1b substrate) by compression milling, and the energy input can be controlled by the milling time. The enzymatic hydrolysis yeilds from cellulosic materials pretreated by compression milling also vary significantly depending on the source and kind, the composition milling also vary significantly depending on the source and kind, the composition (contents of lignin and other components), and the structure. The power requirements for compression milling which renders equivalent hydrolysis yields also depend on the source and kind of lignocellulosics to be pretreated. For newspaper, the specific energy input required for 55% sugar yield is estimated as 0.3 kWh/lb substrate including 15% power loss. The additional sugar yield gained from the enzymatic hydrolysis of compression‐milled newspaper (over and above the sugar yield of untreated substrate) is determined as 453 g sugar/kWh energy input.
Fermentation of Bacillus thuringiensis for exotoxin production: Process analysis study
Authors: Holmberg Andrea , Sievänen Risto , Carlberg Gunnel
Published: December 2004

The exotoxin produced by certain serotypes of Bacillus thuringiensis was used as a means of microbiological control of the larval development of flies. The optimal batch cultivation conditions with respect to pH, temperature, aeration, agitation, and initial concentration of growth‐limiting substrate were determined. A dynamic model describing the process was designed and fitted to the experimental data. The application of a method for estimating exotoxin and bacterial concentrations from on‐line measurable quantities such as oxygen consumption and heat production is presented.
Product formation in the continuous culture of microbial populations grown on carbohydrates
Authors: Baskir Cyril Isadore , Hansford Geoffrey Spearing
Published: December 2004

Experimental studies of the growth of a natural microbial population on a synthetic liquid effluent containing sugar, sodium alginate, and nutrients showed that: (I) the concentration of substrates in the feed to an activated sludge process exerts a significant effect upon its effluent chemical oxygen demand (COD) and (ii) there is an optimum sludge age for achieving minimum effluent COD, given by the relationship: optimum growth rate ∝ (feed COD)0.5. These were explained by incorporating the concept of product formation into existing activated‐sludge theory, which showed that at sludge ages longer than optimum, effluent COD increased due to product formation; at shorter sludge ages, the effluent COD increased owing to an increased concentration of degradable substrates.
Substrate utilization kinetic model for biological treatment process
Authors: Chen Y. R. , Hashimoto A. G.
Published: December 2004

The applicability of Contois' kinetic equation to aerobic and anaerobic treatments of organic wastes is investigated. A refractory coefficient to account for the nonbiodegradable portion of the organic substrates in the digester is incorporated into the kinetic equation. The kinetic equation is applied to the data for aerobic digestions of organic substrates and for anaerobic treatment of dairy wastes. They all show a very good fit of the kinetic equation to the data. Furthermore, the kinetic parameters and the refractory coefficients are shown to be independent of influent organic substrate concentration. This study confirms previous reports that the effluent quality of biological treatment systems for organic wastes depends on influent organic waste concentration. The effect of temperature on the kinetic parameters and the refractory coefficient for anaerobic treatment of sewage sludge are studied. It shows that the kinetic parameters vary with temperature, while the refractory coefficient remains fairly constant. Equations to predict biodegradable treatment efficiency and volumetric substrate utilization rate are also briefly discussed.
Batch‐ and continuous‐culture studies of a methane‐utilizing mixed culture
Authors: Lamb S. C. , Garver J. C.
Published: December 2004

A 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

Pullulanase 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

The 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

The 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

The 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

The 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

Wheat 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

Results 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

The 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

The 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

This 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

Yeast–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

A 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

Applying 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

The 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

A 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

A 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

The 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

Dextransucrase 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

The 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.
Effect of physical and physicochemical pretreatments of wood for SCP production with Chaetomium cellulolyticum
Authors: Chahal D. S. , Moo‐Young M. , Vlach D.
Published: December 2004

Relatively poor SCP production (4.2 mg/L h) was obtained using C. cellulolyticum and ground aspen wood treated with steam at atmospheric pressure for 1 h. The percentage of protein in the final product increased to 21.4% at a specific growth rate of 0.15 h−1 when the wood sample was treated with steam at a higher pressure (280 psig for 4 min) according to the "Stake" process. Alkali treatment (10% and 15% w/w at 121°C for 30 min), known to solubilize hemicelluloses and some of the lignin, gave intermediate results. More complete delignification of wood using NaClO2 increased the protein composition in the final product to 37.9%, at a specific growth rate of 0.19 h−1. Cellulose utilization was lowest (12.4%) in the case of the wood treated with steam at atmospheric pressure; it was higher at 75.3 and 78.5% for wood treated with NaOH at 10 and 15% w/w levels, respectively. The cellulose utilization was highest (90%) for wood treated with NaClO2.
Kinetic modeling of a multiple immobilized enzyme system. I. Development and testing of the model
Authors: Mercer D. G. , O'Driscoll K. F.
Published: December 2004

A kinetic model for the reaction sequence catalyzed by coimmobilized invertase and glucose oxidase with a sucrose substrate in a tubular reactor has been developed. The computerized mathematical model employs and orthogonal collection technique for solving oxidase were coimmobilized in poly(2‐hydroxyethlmethacrylate) gels and used in a continuous flow packed‐bed tubular reactor system. In addition to describing the development of the kinetic model, this article compares experimentally determined reactor effluent concentrations for various sucrose feed solutions to those predicted by the model. Variations between experimental and predicted reactor effluent concentrations were found to be on the micromolar level for sucrose feed concentrations as low as 1.38mM.
γ‐Ray‐induced degradation of lignocellulosic materials
Authors: Han Y. W. , Timpa J. , Ciegler A. , Courtney J. , Curry W. F. , Lambremont E. N.
Published: December 2004

Lignocellulosic plant materials were treated with various swelling agents and exposed to γ radiation from 60Co or 137Cs. At dosages of 50 Mrad or above, lignocellulosic materials were extensively degraded and solubilized in water. Addition of water, NaOH, or H2SO4 to the substrate increased the degree of solubilization. Complete solubilization was achieved for samples of sugarcane bagasse, newspaper, cotton linters, cotton cloth, sawdust, and α‐cellulose powder. About 35% total sugar and 5% reducing sugar per dry weight of sugarcane bagasse could be obtained by this method. Most of the soluble carbohydrates seemed to be disaccharides or larger molecules and glucose degradation products. Solubilization of cellulose was dosage dependent and although the rate of solubilization was increased by adding alkali, released sugar was further decomposed by the alkali and by high dosage of radiation.
Kinetics of thermal denaturation of antithrombin III
Authors: Mitra G. , Schneider P. M. , Lundblad J. L.
Published: December 2004

Purified antithrombin III (AT III), a single‐chain human plasma glycoprotein, molecular weight 58,000 daltons, and one of the major serine protease inhibitors, was heated in the 60–70°C range for inactivating possible contaminations by hepatitis B virus (HBV). Loss of inhibitory activity, unfolding of tertiary structure, and the rate of aggregate formation of AT III were monitored experimentally during heatig. Sucrose and sodium citrate were demonstrated to stabilize the protein. From the rate data the calculated activation energies (E) showed Etert. struct. < Ebiol. act. < Eaggreg. indicating the order (lower activation energy process first) in which heat causes these changes in the protein molecule. The activation energy corresponding to denaturation of HBV was estimated to be at least fourfold lower than that associated with the unfolding of the tertiary structure of the protein. Purified AT III, thus stabilized and pasteurized, should be therapeutically effective, and the risk for transmission of hepatitis B should be decreased significantly.
Effect of surface shear stress on the attachment of Pseudomonas fluorescens to stainless steel under defined flow conditions
Authors: Duddridge J. E. , Kent C. A. , Laws J. F.
Published: December 2004

The application of the radial‐flow growth chamber to the study of the initial stages of bacterial adhesion to surfaces under flowing conditions is reported. The adhesive properties of the bacterium Pseudomonas fluorescens (NCIB 9046) to stainless steel (type AISI 316) were found to be highly dependent on surface shear stress and the time and concentration of cells used in the incubation procedure. Maximum levels of adhesion occurred in zones of lowest surface shear stress, particularly less than 6–8 Nm−2. Adhesion was still noticeable at shear stresses even up to 130 Nm−2. Significant detachment of cells from a monolayer attached under static conditions was found to occur at surface shear stresses in excess of 10–12 Nm−2.
Production of surfactant by Arthrobacter paraffineus ATCC 19558
Authors: Duvnjak Z. , Cooper D. G. , Kosaric N.
Published: December 2004

A. paraffineus ATCC 19558 grown in MMSM (modified mineral salts medium) containing hydrocarbon produced surfactant, with a maximum CMC−1 value obtained by using hexadecane as the carbon source. No activity of surface active agent in whole broth was observed when glucose was used in the MMSM instead of hexadecane. The biomass concentration obtained with glucose was about 40% of that obtained with hexadecane. Glucose (4%) in the medium contaning hexadecane caused a 27 and 21% decrease of biomass and surfactant concentrations, respectively. In the process of surfactant production, glucose can be used as a carbon source for growth, and hexadecane added later can serve for production of the surface active agent. The optimum temperature for production of surfactant is 27°C.
Strategies for penicillin fermentation in tower–loop reactors
Authors: König Burghard , Schügerl Karl , Seewald Christian
Published: December 2004

Since it has not been possible to produce penicillin in tower–loop reactors with highly viscous filamentous molds ofPenicillium chrysogenumwhich are employed in stirred‐tank reactors, a new strategy has been developed to avoid the formation of this morphology and to use the pellet form of the fungi. When employing definite impeller speeds in the subculture in connection with definite inoculum amounts and substrate concentrations in the main culture (bubble column), it is possible to generate a suspension of isolated small pellets, which shows a low broth viscosity up to a sediment content of 45% over the entire fermentation time. Volumetric mass‐transfer coefficientskLasare by a factor of 4 to 5 higher in these pellet suspensions than in filamentous broths. It was easy to maintain the necessary oxygen supply for penicillin production in these pellet suspensions. Under these conditions the specific penicillin productivities were higher with regard to power input (up to 90%), biomass, and consumed substrate than in the stirred‐tank reactors with highly viscous filamentous morphology of the fungi. Under nonoptimized operating conditions the absolute penicillin production in the tower loop was 35% lower than in the stirred‐tank reactor due to lower possible biomass concentrations. The separation of the biomass, and therefore the penicillin recovery, is much simpler when employing pellets. It is shown how the particular mass transfer resistances at the gas/liquid and liquid/pellet interfaces and within the pellets change with the pellet diameter. There should be a particular pellet diameter at which penicillin productivity has its maximum. These investigations indicate that the use of tower‐loop reactors can, in the future, be an alternative for more economical penicillin production methods.
Properties of hydrocarbon‐in‐water emulsions stabilized by Acinetobacter RAG‐1 emulsan
Authors: Zosim Zinaida , Gutnick David , Rosenberg Eugene
Published: December 2004

Emulsan is a polymeric extracellular emulsifying agent produced by Acinetobacter RAG‐1. Hydrocarbon‐in‐water emulsions (Vf of hydrocarbon of 0.01–0.10) were stabilized by small quantities of emulsan (0.02–0.2 mg/mL). Although both aliphatic and aromatic hydrocarbon emulsions were stabilized by emulsan, mixtures containing both aliphatics and aromatics were better substrates for emulsan than the individual hydrocarbon by themselves. The emulsan remained tightly bound to the hydrocarbon even after centrifugation as determined by (a) residual emulsan in the aqueous phase and (b) the fact that the resulting “cream” readily dispersed in water to reform stable emulsions. With hexadecane‐to‐emulsan weight ratio of 39 and 155, the noncoalescing oil droplets had average droplet diameters of 2.0 and 4.0 μm, respectively. Dialysis studies showed that the water‐soluble dye Rhodamine B adsorbed tightly to the interface of hexadecane–emulsan droplets although the dye did not bind to either hexadecane or emulsan alone. At saturating concentrations of dye, 2.2 μmol of dye were bound per mg emulsan.
Conversion of D‐xylose to ethanol by the yeast Pachysolen tannophilus
Authors: Slininger P. J. , Bothast R. J. , Van Cauwenberge J. E. , Kurtzman C. P.
Published: December 2004

The yeast Pachysolen tannophilus was found to be capable of converting D‐xylose to ethanol. Batch cultures initially containing 50 g/L D‐xylose yielded 0.34 g of ethanol per gram of pentose consumed. Aerobic conditions were required for cell growth but not for ethanol production. Both alcohol formation and growth were optimum when incubation temperature was 32°C, when pH was near 2.5, and when D‐xylose and ethanol concentrations did not exceed 50 and 20 g/L, respectively.
Fuel alcohol biosynthesis by Zymomonas anaerobia: Optimization studies
Authors: Kosaric N. , Ong S. L. , Duvnjak Z.
Published: December 2004

The optimum operating conditions for growth and ethanol production of Zymomonas anaerobia ATCC 29501 were established. The optimum pH range and temperature were found to be 5.0–6.0 and 35°C, respectively. Based on the results obtained from the temperature optimization study, an Arrhenius‐type temperature relationship for the specific growth rate was developed. The growth and ethanol production of this microbe also have been optimized in terms of concentrations of glucose, essential nutrients, and minerals. With optimum medium and operating conditions, an ethanol concentration of 96 g/L was obtained in 23 h. Both growth and ethanol yield coefficients in dependence on initial glucose concentrations were determined.
Diffusion resistance and enzyme activity decay in a pellet
Authors: Verhoff F. H. , Goldstein W. E.
Published: December 2004

The effective enzyme activity decay can be decreased by diffusion limitation in the immobilized pellet. Thiele modulus changes and/or poisoning of various enzyme forms are two phenomena which are influenced by diffusion limitation. This article considers these effects on enzyme decay as applied to glucose isomerase.
Kinetics of the acid precipitation of soya protein in a continuous‐flow tubular reactor
Authors: Virkar P. D. , Hoare M. , Chan M. Y. Y. , Dunnill P.
Published: December 2004

The acid precipitation of soya protein was studied in a continuous‐flow tubular reactor under conditions of turbulent flow. Preliminary batchwise experiments of a semiquantitative nature were also carried out on a bench‐scale reactor to better define the parameters affecting precipitate growth. The experiments indicated the dominant growth mechanism to be the aggregation of primary precipitate particles produced by the contacting of the protein and acid streams. The rate of particle growth was observed to rise with an increase in the protein concentration as well as with greater intensity of turbulence. The final mean particle size decreased with increased intensity of turbulence. A theoretical model was set up to simulate the growth of the precipitate particles.
The mechanism of thorium biosorption by Rhizopus arrhizus
Authors: Tsezos M. , Volesky B.
Published: December 2004

Inactive cells of Rhizopus arrhizus have been documented to exhibit a high thorium biosorptive uptake (170 mg/g) from aqueous solutions. The mechanism of thorium sequestering by this biomass type was investigated following the same method as for the uranium biosorption mechanism. The thorium sequestering mechanism appeared somewhat different from that of uranium. Experimental evidence is presented which indicates that, at optimum biosorption pH (4), thorium coordinates with the nitrogen of the chitin cell wall network and, in addition, more thorium is absorbed by the external section of the fungal cell wall. At pH 2 the overall thorium uptake is reduced. The kinetic study of thorium biosorption revealed a very rapid rate of uptake. Unlike uranium at optimum solution pH, Fe2+ and Zn2+ did not interfere significantly with the thorium biosorptive uptake capacity of R. arrhizus.
Immobilized enzymes: Electrokinetic effects on reaction rates in a porous medium
Authors: Ruckenstein Eli , Kalthod Dilip G.
Published: December 2004

The effect of the internal diffusion and electrical surface charge on the overall rate of a reaction catalyzed by an enzyme immobilized on a porous medium are examined. Effectiveness factors have been calculated which compare the global reaction rate to that existing in the absence of the internal diffusion and/or the electrical field. The surface charge, assumed to arise from the dissociation equilibria of the acidic and basic surface groups of the enzyme, generates an electrical double layer at the pore surface. The double‐layer potential is governed by the Poisson‐Boltzmann equation. It is shown that the diffusion potential can be characterized by a modulus which depends upon the surface reaction rate, the charges and diffusivities of the substrate and products, the ionic strength, and the pore dimensions. The flux of a charged species in the pore occurs under the influences of the concentration gradient and the electrical potential gradient. The governing equations are solved by an iterative numerical method. The effects of pH, enzyme concentration, and substrate concentration on the rates of two different hydrolysis reactions catalyzed by immobilized papain are examined. The release of H+ in one of the reactions causes the lowering of internal pH, and also a constancy of the internal pH when the external pH in creases beyond a certain value. The latter reaction also shows a maximum in the reaction rate with respect to enzyme concentration. The reaction not involving H+ as a product shows a maximum in the reaction rate with respect to external pH, but a monotonic increase in the reaction rate as the enzyme concentration increases.
Kinetics and activation energetics of death in Saccharomyces cerevisiae induced by sulfur dioxide
Authors: Anacleto J. , van Uden N.
Published: December 2004

Death of Saccharomyces cerevisiae induced by sulfur dioxide (K2S2O2 was used as the SO2 source) followed saturation kinetics. The enthalpy of activation of death was not affected by concentration over the range tested (5–150) mg/L of (K2S2O2 at pH 3.4) and averaged 3.6 × 104 cal/mol as compared with 8.5 × 104 cal/mol for ΔH‡ of thermal death. The entropy of activation of death was hyperbolic function of the sulfur dioxide concentration, extrapolated at zero concentration to ΔS0‡ = 36.8 cal mol−1 K−1 and tended to ΔΔSmax‡ = 13.2 cal mol−1 K−1 at saturating concentration, yielding a dis0sociation constant of 5.8 × 10−1 M sulfur dioxide. As was predicted from these results, In Kd (the specific rate of death induced by sulfur dioxide) was hyperbolic function of concentration under isothermic conditions and extrapolated toa finite value at zero concentration. The Arrhenuis plots and the ΔS± plot versus concentration revealed the occurrence of substrate inhabitation of the death effect at high concentrations (above 60 mg/L K2S2O2 at pH 3.4). A model is presented involving two types of receptor sites for sulfur dioxide on the cell surface, on directly connected with the death process, the other modulating its entropy of activation.
Anaerobic fluidized bed whey treatment
Authors: Boening Paul H. , Larsen Vidar F.
Published: December 2004

Anaerobic treatment of moderate strength lactic casein why permeate [2000–7000 mg/L soluble chemical oxygen demand (SCOD)] is possible in fluidized bed reactors. Removal efficiencies up to 90% were obtained at organic removal rates of 7.7 kg SCOD M−3 day−1 and efficiencies of 70% were obtained at organic removal rates of 19.5 kg SCOD M−3 day−1, both at 35°C. A removal rate of 3.0 kg SCOD M−3 day−1 at 50% removal efficiency was obtained at 15°C. Nutrient requirements were much lower than for CSTR systems, and no supplemental nitrogen or phosphorus was required. Removal rates increased and removal efficiency decreased as the organic loading increased. Microorganism concentration increased with decreasing temperature, compensating for reduced reaction rates at lower temperatures.
Competition between two microbial populations in a nonmixed environment: Effect of cell random motility
Authors: Lauffenburger D. , Calcagno P. B.
Published: December 2004

In a nonmixed environment, bacterial population growth can be influenced significantly by cell motility properties as well as by growth kinetic properties. Therefore, in a situation of competition between two bacterial populations for a single chemical nutrient in a nonmixed environment, the outcome may depend upon the respective cell motility properties. In this article, the authors have presented a simple mathematical model for competitive growth of two randomly motile (i.e., possessing no chemotactic behavior) populations in a finite nonmixed region. An understanding of the behavior of this model should provide insight into the behavior of a number of common microbial competition problems. Analysis of this model yields the following results: (1) There may be as many as three possible non‐trivial steady‐state (or long‐time) configurations: when species 1 survives, species 2 dies out; when species 2 survives, species 1 dies out; and species 1 and species 2 coexist. (2) The coexistence state can exist even though one species possesses a smaller intrinsic growth rate constant at all nutrient concentrations, if that same species is sufficiently less motile than the other species. (3) In fact, the species with the smaller maximum specific growth rate may grow to a larger population than the other. (4) The possibility of coexistence can be decided essentially from the results for single population growth.