bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of steam explosion as a method for increasing susceptibility of sugarcane bagasse to enzymatic saccharification
Authors: Morjanoff P. J. , Gray P. P. 
Published: December 2004

AbstractThe technique of autohydrolysis steam explosion was examined as a means for pretreatment of sugarcane bagasse. Treatment conditions were optimized so that following enzymatic hydrolysis, pretreated bagasse would give 65.1 g sugars/100 g starting bagasse. Released sugars comprised 38.9 g glucose, 0.6 g cellobiose, 22.1 g xylose, and 3.5 g arabinose, and were equivalent to 83% of the anhydroglucan and 84% of the anhydroxylan content of untreated bagasse. Optimum conditions were treatment for 30 S with saturated steam at 220°C with a water‐to‐solids ratio of 2 and the addition of 1 g H2SO4/100 g dry bagasse. Bagasse treated in this manner was not inhibitory to fermentation by Saccharomyces uvarum except at low inoculum levels when fermentation time was extended by up to 24 h. Pretreated saccharified bagasse was inhibitory to Pachysolen tannophilus and this was attributed to the formation of acetate from the hydrolysis of acetyl groups present in hemicellulose. The major advantage of the pretreatment is the achievement of high total sugar yield with moderate enzyme requirement and only minor losses due to sugar decomposition.
Kinetics of growth and phosphate uptake in pure culture studies of Acinetobacter species
Authors: Hao Oliver J. , Chang C. H. 
Published: December 2004

AbstractAcinetobacter has been found to be the major species responsible for mediating biological phosphate removal. The growth kinetics and phosphate uptake were investigated for an isolated Acinetobacter strain growing in a defined medium. The phosphate uptake is dependent on growth rate, temperature, and pH. Polyphosphate granules occurred in a balanced growth stage. The maximum phosphorus content in cells was 4.8% at the dilution rate of 12 day−1. The specific phosphate uptake rate was found to be a quadratic polynomial function of the dilution rate. Increased calcium (up to 36 mg/L) and magnesium (up to 15 mg/L), and the addition of yeast extract (100 mg/L), primary effluent (20%), and fluoride (10 mg/L) did not affect phosphate uptake. Anaerobic conditioning (N2 stripping), low pH (CO2 stripping), and addition of sodium acetate under anaerobic conditions failed to stimulate immediate phosphate release. Nevertheless, After 21–24 h, the phosphate release was ca. 3, 5, and 15 mg P/g cell, respectively, for N2 purging, the addition of acetate, and CO2 purging. For two‐stage completely stirred reactor operation, there was negligible phosphate overplus at the second reactor when phosphate was added, when the first reactor was subjected to phosphate limitation. When both phosphate and carbon limited the growth in the first reactor, there was slight phosphate accumulation under endogenous respiration conditions in the second reactor.
Kinetics of ethanol production during the reactor feeding phase in constant feb‐batch fermentation of molasses
Authors: Borzani Walter 
Published: December 2004

AbstractDuring the fermentor feeding phase in constant fed‐batch ethanol fermentation of molasses, the ethanol production rates are constant and are correlated to the sugar feeding rates by a Monod‐like equation. The parameters of this Monod‐like correlation depend on the sugars concentration of the feeding mash. A model is proposed to explain the constancy of the ethanol production rate experimentally observed. From the Monod‐like correlation it is possible to evaluate the maximum value of the mash feeding rate to be used in order to have a completely fermented medium just at the end of the feeding phase.
Evaluation of true kinetic parameters for reversible immobilized enzyme reactions
Authors: Ishikawa Haruo , Tanaka Takenori , Kurose Katsuo , Hikita Haruo 
Published: December 2004

AbstractFor a reversible one‐substrate reaction system that follows the Haldane reaction mechanism, a new and effective method has been proposed to extract true or intrinsic kinetic parameters of immobilized enzymes from diffusion limited rate data. The method utilizes the effectiveness factors correlated in terms of the general modulus defined by Aris and Bischoff, and a new modulus defined in the present study. It requires a trial‐and‐error calculation, but only a few data points. Furthermore, it provides a saving of materials such as substrates and enzymes, and takes less time for experiments compared to the initial rate methods. The usefulness of the method is demonstrated by determining the kinetic parameters for membrane bound fumarase which catalyzes the reaction of the conversion of fumarate to L‐malate, for which the equilibrium constant is ca. 4.
Regulation of lac operon expression in mixed sugar chemostat cultures
Authors: Ray N. G. , Vieth W. R. , Venkatasubramanian K. 
Published: December 2004

AbstractExpression of the lactose (lac) operon in the Escherichia coli chromosome has been studied in mixed‐sugar chemostat cultures under steady‐state and transient conditions. A unified model has been formulated which involves regulation of active inducer (lactose) transport, promoter–operator regulated expression of the lac operon, glucose‐mediated inducer exclusion, and catabolite repression. The model of the lac operon control system focuses on the molecular interactions among the regulatory species and the genetic control elements for the initiation of transcription. The role of catabolite modulator factor (CMF) in the regulation of transcription is described. The modeling of glucose‐mediated regulation of intracellular cyclic adenosine monophosphate (cAMP) and inducer exclusion is based on the recently elucidated mechanisms of the involvement of the PTS (phosphoen‐olpyruvate dependent sugar transport system) enzymes, in the presence of glucose, in regulation of adenylate cyclase and non‐PTS sugar transport proteins (i.e. per‐meases). The adequacy of the unified model was verified with experimental data.
Modeling biofilm kinetics for a low‐loaded expanded‐bed anaerobic reactor
Authors: Wang Yi‐Tin , Suidan Makram T. , Rittmann Bruce E. 
Published: December 2004

AbstractThe effect of surface coverage of biomass on biofilm kinetics in an expanded‐bed, granular activated carbon an aerobic reactor was evaluated. Acetate was used as the sole organic carbon source. An assumption of 10% surface coverage of biofilm was examined and compared to 100% coverage. Best estimated values of ka and Ksa did not differ significantly from one case to the other. The confidence region analysis also showed that the biofilm was fully penetrated in the expanded‐bed reactor for the case of 10% coverage, as well as when 100% coverage was assumed. Because the biofilm was fully penetrated, a model having no internal diffusion resistance and using the best estimates of ka and Ksa obtained from the 10 and 100% coverage assumptions was capable of giving good predictions of effluent acetate concentrations for an in dependent experiment having a reduced liquid detention time. Consideration of biofilm surface‐loading criteria demonstrated how the results can be applied to other reactors for the purpose of predicting when the extent of surface coverage and internal diffusion resistance are not significant factors in biofilm modeling.
Production of ethanol by Saccharomyces cerevisiae under high‐pressure conditions
Authors: Thibault Jules , LeDuy Anh , Côté François 
Published: December 2004

AbstractA research project was initiated to examine the possibility of using supercritical carbon dioxide for in situ recovery of ethanol during its production by yeast Saccharomyces cerevisiae. As a preliminary step, it was necessary to study the behavior of ethanol production under high‐pressure conditions, up to 7 MPa (1000 psi). The results show that pressure has a significant inhibiting effect on the production of ethanol. There is a significant decrease in the initial rate of production as well as in the final ethanol concentration as pressure is increased. This decrease is more significant when carbon dioxide is used to pressurize the fermentor. The pressure affects the ability of the cells to produce ethanol in a reversible way. When the fermentor is returned to atmospheric conditions, the reaction resumes its normal fermentation rate.
The effect of temperature and pH on ethanol production by free and immobilized cells of Kluyveromyces marxianus grown on Jerusalem artichoke extract
Authors: Bajpai Pratima , Margaritis Argyrios 
Published: December 2004

AbstractThe effect of temperature and pH on the kinetics of ethanol production by free and calcium alginate immobilized cells of Kluyveromyces marxianus grown on Jerusalem artichoke extract was investigated. With the free cells, the ethanol and biomass yields were relatively constant over the temperature range 25–35°C, but dropped sharply beyond 35°C. Other kinetic parameters, specific growth rate, specific ethanol production rate, and specific total sugar uptake rate were maximum at 35°C. However, with the immobilized cells, ethanol yield remained almost constant in the temperature range 25–45°C, and the specific ethanol production rate and specific total sugar uptake rate attained their maximum values at 40°C. For the pH range between 3 and 7, the free‐cell optimum for growth and product formation was found to be ca. pH 5. At this pH, the specific growth rate was 0.35 h−1 and specific ethanol production rate was 2.83 g/g/h. At values higher or lower than pH 5, a sharp decrease in specific ethanol production rate as well as specific growth rate was observed. In comparison, the immobilized cells showed a broad optimum pH profile. The best ethanol production rates were observed between pH 4 and 6.
Mixed solvent systems for recovery of ethanol from dilute aqueous solution by liquid–liquid extraction
Authors: Mitchell R. J. , Arrowsmith A. , Ashton N. 
Published: December 2004

AbstractDistribution coefficients and selectivities of a number of mixed solvent systems have been determined in order to assess their suitability in preferentially extracting ethanol from aqueous solution. The measured values of distribution coefficients and selectivities differ substantially from the values estimated by interpolating between the pure solvents.
Oxygen transfer in animal cell culture medium
Authors: Lavery M. , Nienow A. W. 
Published: December 2004

AbstractBoth kLa and kL measurements were carried out by an unsteady state technique at impeller speeds ranging from 1.6 to 5.8 s−1 in a mechanically agitated animal cell culture vessel of working volume 1.5 L. Checks were made that the time constant of the oxygen electrode was negligible compared to the time for aeration and that the oxygen electrode reading was not a function of agitator speed in the range employed. The kL values by surface aeration of (1.18–3.54) × 10−5 m/s and kLa values by sparged aeration of (2.8–8.5) × 10−4 s−1 were found. The former are in reasonable agreement with published experimental values and the latter in accord with values estimated from published correlations based on agitator power input and aeration rate. The fluids used were water, basal medium, and basal medium supplemented with 5% (v/v) foetal calf serum; for each of these, kL and kLa values were similar. However, the addition of silicone antifoam (6 PPM) reduced the kLa value by ca. 50%.
Continuous‐culture studies of synthesis and regulation of extracellular β(1‐3) glucanase and protease enzymes from Oerskovia xanthineolytica
Authors: Andrews B. A. , Asenjo J. A. 
Published: December 2004

AbstractThis article describes the synthesis and regulation of β(1‐3)glucanase and protease enzymes from the cell lytic system of Oerskovia xanthineolytica LL‐G109 in continuous culture using different concentrations of carbon source (glucose) and inducer (glucan). These two enzyme activities are the main components of a lytic system capable of lysing and disrupting whole yeast cells; it is subject to catabolite repression by glucose and is induced by yeast glucan. Peaks of β(1‐3)glucanase and protease activity are obtained at dilution rates of between 0.05 and 0.15 h−1. The glucanase‐protease ratio is very high compared to other strains. At dilution rates above 0.15 h−1 all activities are similar to those obtained in batch culture. The lytic enzyme system appears to contain several β(1‐3)glucanase enzymes. In continuous culture both productivity and enzyme concentrations are greatly in creased when compared to batch culture, 11‐ and 4.4‐fold, respectively.
Periodic forcing of microbial cultures: A model for induction synchrony.
Authors: Hjortso Martin A. 
Published: December 2004

AbstractPeriodic environmental shifts have been used to induce synchrony in many different microbial populations. In this article, the induction synchrony phenomenon is analyzed using an age distribution model in which the age at which the cells divide is subjected to periodic forcing. It is found that synchrony will occur whenever the period of the forcing lies in the interval between the youngest and the oldest division age that occur in the population during the forcing. The analysis also predicts that under certain conditions it should be possible to obtain a multimodal synchrony in which cells in the population are distributed among a set of discrete, synchronized cell lines. The behavior of the age distribution when the conditions for synchrony are not satisfied is briefly explored. It is found that the age distribution model is able to exhibit a very rich spectrum of possible dynamic behavior. Many of the phenomena observed can be thought of in terms that are familiar from nonlinear analysis, such as stable and unstable limit cycles, period doubling, halving, and chaos. The richness of dynamic behavior opens the possibility that environmental shifts or periodic forcing could be used as a powerful tool in discriminating models of microbial kinetics and cell cycle control.
Preservation of potential fermentables in sweet sorghum by ensiling
Authors: Linden James C. , Henk Linda L. , Murphy Vincent G. , Smith D. H. , Gabrielsen Byron C. , Tengerdy Robert P. , Czako Lajos 
Published: December 2004

AbstractPressed and wilted samples of sweet sorghum [Sorghum bicolor (L.) Moench var. Rio] were ensiled for periods up to 155 days. A kinetic study of the biochemical changes which occurred during ensiling showed that in wilted sorghum ensilage invert sugars and mannitol levels collectively were maintained at 65% of the original ferment able sugar content of the sorghum. The acidic environment produced by ensiling also served as a pretreatment that resulted in enhanced yields of reducing sugar when the sorghum was contacted with cellulolytic enzymes. The quantity of sugar obtained from enzymatic hydrolysis more than compensated for carbohydrate used by organisms during the ensiling process. Both Saccharomyces uvarum and Clostridium acetobutylicum were able to ferment a medium constituted from pressed sorghum juice and the solution resulting from enzymatic hydrolysis of sweet sorghum ensilage.
Influence of anions on metal adsorption by Rhizopus arrhizus biomass
Authors: Tobin J. M. , Cooper D. G. , Neufeld R. J. 
Published: December 2004

AbstractThe presence of anions in solution was found to inhibit the uptake of La3+, Cd2+, Pb2+, UO, and Ag+ by Rhizopus arrhizus biomass. The effects ranged from total inhibition of Cd2+ and Pb2+ uptake at equimolar concentrations of EDTA to no change in uptake of La3+ or UO at 12‐fold molar excesses of Cl− or CO. No anion was found to enhance metal uptake levels, and the degree of inhibition generally followed the series:

The chemical equilibrium model REDEQL2 was adapted to treat metal uptake by R. arrhizus biomass and used to predict the effects of anions in solution. Comparisons with the experimental results are made and discussed in light of the assumptions underlying the model.
Separation of dilute aqueous butanol and acetone solutions by pervaporation through liquid membranes
Authors: Matsumura Masatoshi , Kataoka Hiroshi 
Published: December 2004

AbstractA simultaneous extraction‐stripping process is proposed for separating volatile products from fermentation broths, it is based on pervaporation through a liquid membrane supported with a hydrophobic porous membrane. The liquid membrane prepared with oleyl alcohol was selected as the most suitable for separating volatile products resulting from acetone‐butanol fermentation. The separation performance and stability of the oleyl alcohol liquid membrane were investigated by using dilute aqueous butanol and acetone solutions. The oleyl alcohol liquid membrane was found to be superior by far in both selectivity and permeability of butanol to the better known silicone rubber membrane in its high selectivity for alcohols. Using the oleyl alcohol liquid membrane, the dilute aqueous butanol solutions of around 4 g/L obtained in acetone‐butanol fermentation could be concentrated up to 100 times. The stability of this liquid membrane was also quite good as long as the surface tension of the feed solution was less than the critical surface tension of the support membrane. No change in the separation performance was found after the continuous usage in a long period of 100 h.
Microencapsulation of human fibroblasts in a water‐insoluble polyacrylate
Authors: Boag Alexander H. , Sefton Michael V. 
Published: December 2004

AbstractViable human diploid fibroblasts have been micro‐encapsulated in EUDRAGIT RL, a commercially available water‐insoluble polyacrylate, by an interfacial precipitation technique. Cells in medium and polymer solution (in diethyl phthalate) were coextruded and formed into droplets by a coaxial air stream. The droplets fell into a corn‐oil/mineral‐oil mixture to extract the solvent to precipitate the polymer around the cells. Capsules were ca. 500 μm in diameter depending on the air flowrate with a ca. 10‐μm thick wall. When collagen (1 mg/mL) was added to the cell suspension prior to encapsulation and base‐washed corn oil was used, cell growth occurred with one doubling achieved after five to six days as the collagen gel contracted inside the capsule. In the absence of collagen, cells spread on the inner wall of the capsule but did not grow, presumably because the surface charge on the capsule was inadequate. In similar fashion fibroblasts spread but did not grow on films of EUDRAGIT RL but did grow on blends of EUDRAGIT RL and EUDRAGIT E containing 10–30% of the latter more highly aminated polyacrylate. Although not suitable for anchorage‐dependent cell growth by itself, EUDRAGIT RL has been suitable as a model polymer to demonstrate the feasibility of using water insoluble polyacrylates and organic solvents and nonsolvents for the micro‐encapsulation of fibroblasts. Such microcapsules are of potential interest as a mode of large scale tissue culture for the production of novel therapeutic agents.
An enzyme electrode for on‐line determination of ethanol and methanol
Authors: Belghith Hafedh , Romette Jean‐Louis , Thomas Daniel 
Published: December 2004

AbstractSince a stable alcohol oxidase with a high specific activity is not commercially available, we propose to produce and purify this enzyme from a strain of the yeast Hansenula polymorpha. This alcohol oxidase was immobilized into a gelatin matrix and its activity was estimated by a pO2 sensor. The enzyme electrode obtained was then used in a continuous flow system to measure methanol or ethanol concentrations. The sample oxygen content dependence of the signal was minimized by the support properties. Measuring time for each sample were less than two minutes including response data treatment and rinsing step. The enzyme electrode response was set for ethanol from 0.5mM to 15mM and for methanol from 10mM to 300mM. On repeated use, the electrode signal for 10mM of ethanol was stable for at least 500 assays. Analysis have been performed in different beverages such as wine and beer, and the results compared to those obtained with classical methods of analysis.
New instrument for on‐line viscosity measurement of fermentation media
Authors: Picque D. , Corrieu G. 
Published: December 2004

AbstractIn an attempt to resolve the difficult problem of on‐line determination of the viscosity of non‐Newtonian fermentation media, the authors have used a vibrating rod sensor mounted on a bioreactor. The sensor signal decreases nonlinearly with increased apparent viscosity. Electronic filtering of the signal damps the interfering effect of aeration and mechanical agitation. Sensor drift is very low (0.03% of measured value per hour).On the rheological level the sensor is primarily an empirical tool that must be specifically calibarated for each fermentation process. Once this is accomplished, it becomes possible to establish linear or second‐degree correlations between the electrical signal from the sensor and the essential parameters of the ferementation process in question (pH of a feremented milk during acidification, concentration of extra cellular polysaccharide). In addition, by applying the power law to describe the rheological behavior of fermentation media, we observe a second‐order polynomial correlation between the sensor signal and the behavior index (n).
Specific and nonspecific glucanases from Trichoderma viride
Authors: Beldman G. , Voragen A. G. J. , Rombouts F. M. , Searle‐Van Leeuwen M. F. , Pilnik W. 
Published: December 2004

AbstractSix endoglucanases (Endo I, II, III, IV, V, and VI), three exoglucanases (Exo I, II, and III), and a β‐glucosidase (β‐gluc I) isolated from a commercial cellulase preparation of Trichoderma viride origin were examined as to their activities on xylan ex oat spelts. Endo I, II, and III as well as Exo II and III showed no activity toward xylan and were classified as specific glucanases. Less specificity was found for the endoglucanases Endo IV, V, and VI, Exo I, and β‐gluc I, whose enzymes were able to hydrolyze xylan. With respect to product formation these xylanolytic cellulases fit the classification of xylanases generally accepted in the literature. Kinetic experiment with xylan, CM‐cellulose, and p‐nitrophenyl‐β‐D‐glucoside revealed that Endo IV, V, an VI and Exo I prefer to hydrolyze β‐1, 4‐D‐glucosidic linkages. β‐Gluc I showed no clear substrate preference.
Adaptive control of anaerobic digestion processes—a pilot‐scale application
Authors: Renard P. , Dochain D. , Bastin G. , Naveau H. , Nyns E.‐J. 
Published: December 2004

AbstractA simple adaptive control algorithm, for which theoretical stability and convergence properties had been previously demonstrated, has been successfully implemented on a biomethanation pilot reactor. The methane digester, operated in the CSTR mode was submitted to a shock load, and successfully computer controlled during the subsequent transitory state.
A microfibril‐generating factor from the cellulase of Trichoderma reesei
Authors: Krull L. H. , Dintzis F. R. , Griffin H. L. , Baker F. L. 
Published: December 2004

AbstractA combination of ionic strength reduction and diafiltration of Trichoderma reesei cellulate complex through a hollow fiber apparatus of 5000 molecular weight (MW) cutoff and subsequent passage of filtrate over a Spherogel‐TSK 3000‐SW column provided extracts that had the ability to generate microfibrils in filter paper and to disrupt filter paper and corn leaf tissue. Milligram quantities of material obtained from these extracts released small amounts of soluble carbohydrate from filter paper, required ferric iron for increased activity, and contained amino acids. Short fiber formation and disruption of filter paper during interaction with these extracts was enhanced by prior acid treatment and eliminated by prior base treatment. The amount of soluble carbohydrate hydrolyzed in 24 h from filter paper by whole cellulase complex was not changed by first disrupting the substrate with the extracts.