bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solid‐state fermentation of sweet sorghum to ethanol in a rotary‐drum fermentor
Authors: Kargi Fikret , Curme James A. 
Published: December 2004

AbstractSugar compounds present in chopped solid‐sweet sorghum particles were fermented to ethanol in a rotarydrum fermentor (RDF) using an ethanol tolerant yeast strain. The influence of rotational speed of the RDF on the rate of ethanol fermentation was investigated and compared with static flask experiments. The rate of ethanol formation decreased with increasing rotational speed. The maximum rate and extent of ethanol formation were ca. 3.1 g EtOH/L h (based on expressed juice volume) and ca. 9.6 g EtOH/100 g mash, respectively, at 1 rpm rotational speed.
Recycle hollow fiber enzyme reactor with flow swing
Authors: Park Tai Hyun , Kim In Ho , Chang Ho Nam 
Published: December 2004

AbstractThe hollow fiber enzyme reactor with pulsation developed by Kim and Chang (1983) was operated in a differential mode by recycling a substrate solution, in order to assess the efficiency of ultrafiltration swing. The rates of lactose conversion by β‐galactosidase contained in the shell side of the reactor were measured to determine the effects of recirculation rate, pulsation period, and amplitude. The conversion increased with the increase of recirculation flow rate and the amplitude while variation in period affected the conversion relatively little. The maximum increase of 113% in the activity was observed in the reactor with pulsation as compared to that without pulsation. The two‐compartment model well described the experimental data obtained in this study. Square‐wave pulsation was theoretically more effective in increasing conversion than sine wave pulsation. However, in experimental operation the damping effect of the hollow fiber wall narrowed the difference between these two wave forms.
Steady‐state and transient behavior in microbial methanification: II. Mathematical modeling and verification
Authors: Bhatia D. , Vieth W. R. , Venkatasubramanian K. 
Published: December 2004

AbstractIt has been shown that the Upflow Anaerobic Sludge Bed (UASB) system data reported earlier1 cannot be explained by simple Monod‐type substrate consumption patterns. An autoinhibition model was also ruled out because the substrate concentration range over which hysteresis was observed was much larger than such a model would predict. However, propionic and acetic acids were found to inhibit each other's conversion machineries. Since in the UASB system the biocatalyst is flocculated, it was found that a model additionally incorporating this facet of the reactor set‐up could explain the steady‐state data very well. Using the parameters generated from steady‐state data and data from butyric acid step change,1 i.e., the entire set of parameters (Table I), a very good agreement between predicted and observed data was found. International Mathematical and Statistical Libraries (IMSL) and Upjohn's NONLIN library combined with various root‐finding and integrating subroutines were used for parameter estimation. The model thus described was used to predict the response of the UASB system when acetic acid and propionic acid influent concentrations were stepped‐up/down. The agreement between the predicted and observed data was found to be excellent in each case during the step‐up schedule. During the step‐down the data seemed to indicate that the UASB system, like any other chemostat, responded faster than predicted. This could be due to the fact that when the culture has to “gear up” part of the lag time is the time required for the cell to produce the requisite amount of enzymes. In the case of “gearing down” this time is not required and the system responds faster.
Experimental adaptive on‐line optimization of cellular productivity of a continuous bakers' yeast culture
Authors: Rolf Michael J. , Lim Henry C. 
Published: December 2004

AbstractAn adaptive on‐line optimization method that utilizes dynamic model identification has been applied to maximize the cellular productivity of a continuous bakers' yeast culture. Experiments were conducted on a sophisticated computerized fermentation system. Experimental results show that the adaptive on‐line optimization method requires very little a priori information, is easy to implement, converges quickly, adapts to changes in the process, and is stable even when operational difficulties are encountered.
Optimization of organic solvent in multiphase biocatalysis
Authors: Brink L. E. S. , Tramper J. 
Published: December 2004

AbstractThe microbial epoxidation of propene and 1‐butene was used to study some fundamental aspects of two‐liquid‐phase biocatalytic conversions. Introduction of a water‐immiscible organic solvent phase in a free‐cell suspension gave rise to a series of undesired phenomena, e.g., inactivation by the solvent, clotting of biomass, and aggregation of cells at the liquid‐liquid interface. Immobilization of the cells in hydrophilic gels, e.g., calcium alginate, prevented direct cell‐organic solvent contact and the related clotting and aggregation of biomass. However, the gel entrapment did not seem to provide additional protection against the organic solvent. The influence of various organic solvents on the retention of immobilized‐cell activity was related to solvent properties like the polarity (as expressed by the Hildebrand solubility parameter) and the molecular size (as expressed by the molecular weight or molar volume). High activity retention was favored by a low polarity in combination with a high molecular weight. The solubility parameter also proved useful to describe the capacity of various organic solvents for oxygen and alkene oxides. This facilitated the optimization of the solvent polarity.
An ultrafiltration membrane reactor for obtaining experimental reaction rates at defined concentrations of inhibiting sugars during enzymatic saccharification of alkali‐pretreated sallow: Formulation of a simple empirical rate equation
Authors: Frennesson Ingrid , Trägårdh Gun , Hahn‐Hägerdal Bärbel 
Published: December 2004

AbstractThe kinetics of the enzymatic hydrolysis of sodium hydroxide‐pretreated sallow were studied in an ultrafiltration membrane reactor in the presence of different concentrations of glucose. In the UF membrane reactor low‐molecular‐weight products were continuously removed at a low dilution rate and replaced by a buffer solution that contained different concentrations of glucose, which made it possible to keep the inhibiting product concentration constant throughout an experiment. The reaction rate was related to the degree of substrate conversion and a mathematical relationship was formulated that describes the influence of the product concentration on the rate coefficient.
A Mathematical model for ethanol production by extractive fermentation in a continuous stirred tank fermentor
Authors: Kollerup Finn , Daugulis Andrew J. 
Published: December 2004

AbstractExtractive fermentation is a technique that can be used to reduce the effect of end product inhibition through the use of a water‐immiscible phase that removes fermentation products in situ. This has the beneficial effect of not only removing inhibitory products as they are formed (thus keeping reaction rates high) but also has the potential for reducing product recovery costs. We have chosen to examine the ethanol fermentation as a model system for end product inhibition and extractive fermentation and have developed a computer model predicting the productivity enhancement possible with this technique together with other key parameters such as extraction efficiency and residual glucose concentration. The model accommodates variable liquid flowrates entering and leaving the system, since it was found that the aqueous outlet flowrate could be up to 35% lower than the inlet flowrate during extractive fermentation of concentrated glucose feeds due to the continuous removal of ethanol from the fermentation broth by solvent extraction. The model predicts a total ethanol productivity of 82.6 g/L h if a glucose feed of 750 g/L is fermented with a solvent having a distribution coefficient of 0.5 at a solvent dilution rate of 5.0 h−1. This is more than 10 times higher than for a conventional chemostat fermentation of a 250 g/L glucose feed. The model has furthermore illustrated the possible trade‐offs that exist between obtaining a high extraction efficiency and a low residual glucose concentration.
Effect of culture phasing and mannanase on production of cellulase and hemicellulase by mixed culture of Trichoderma reesei D 1–6 and Aspergillus wentii pt 2804
Authors: Ghose T. K. , Panda T. , Bisaria V. S. 
Published: December 2004

AbstractSignificant increase in extracellular cellulase and hemicellulase activities was observed in the biosynthesis of cellulase enzyme in mixed culture fermentation of Trichoderma reesei D 1–6 and Aspergillus wentii Pt 2804 when the A. wentii inoculation was phased by 15 h. The optimal conditions of fermentation by the mixed culture have been established. Presence of mannanase has been found to affect the release as well as activity of cellulase enzyme produced in mixed culture.
A Study of the cellulases produced by three mesophilic actinomycetes grown on bagasse as substrate
Authors: Van Zyl Willem H. 
Published: December 2004

AbstractThe cellulases that strains of Streptomyces albogriseolus, S. nitrosporeus, and Micromonospora melanosporea produce when grown on untreated ballmilled bagasse were investigated. Optimum conditions for extracellular cellulase production and activity were determined to be growth at pH 6.7−7.4 and 25–35°C for 4–5 days and assay at pH 5.0−6.0 and 45–55°C, respectively. The endoglucanases were thermally stable at 50°C, but the Avicelases had a half‐life of approximately 24 h at this temperature. Nearly half of the endoglucanases and almost all of the Avicelases were absorbed on ballmilled bagasse after 15 min incubation at 50°C. The β‐glucosidases were found to be mainly intracellular or cell wall bound. These mesophilic actinomycetes concomitantly produced xylanases and β‐xylosidases with cellulases that, apart from cellobiose and glucose, also release xylose from bagasse. This feature may be advantageous in the commerical application of the enzymes of mesophilic actinomycetes for the saccharification of natural cellulosic substrates.
Performance evaluation of an anoxic/oxic activated sludge system: Effects of mean cell residence time and anoxic hydraulic retention time
Authors: Shieh Wen K. , Chen Chiu Y. 
Published: December 2004

AbstractA laboratory investigation has been undertaken to asses the effects of two operating parameters, mean cell residence time (MCRT) and anoxic hydraulic retention time (HRT), on the performance of an anoxic/oxic activated sludge system. The performance of the system was evaluated in terms of its COD, nitrogen, and biomass characteristics. An activated sludge system is capable of producing a better effluent, in terms of COD and nitrogen characteristics, when it is operated in an anoxic/oxic fashion. A longer MCRT and an adequate anoxic HRT are desirable in the operation of an anoxic/oxic activated sludge system. For the wastewater used in this investigation, the anoxic/oxic unit was capable of producing an effluent with the following characteristics when it was operated at MCRT = 20 days, total system HRT = 10 h, and anoxic HRT = 3–5 h: COD = 15 mg/L; VSS = 10 mg/L; TKN = 1.30 mg/L; NH3− N = 0.60 mg/L; and NO2+ NO3− N = 5.0 mg/L. A uniform distribution of biomass is achievable in an anoxic/oxic activated sludge system because of the intensive recirculation/convection maintained. The provision of an anoxic zone in the aeration tank promotes a rapid adsorption of feed COD into the biomass without an immediate utilization for cell synthesis. This, in turn, results in a high microbial activity and a lower observed biomass yield in the system. A tertiary treatment efficiency is achievable in an anoxic/oxic activated sludge system with only secondary treatment operations and costs. A conventional activated sludge system can be easily upgraded by converting to the anoxic/oxic operation with minor process modifications.
Effects of immobilization on growth, fermentation properties, and macromolecular composition of Saccharomyces cerevisiae attached to gelatin
Authors: Doran Pauline M. , Bailey James E. 
Published: December 2004

AbstractThe kinetic properties of Saccharomyces cerevisiae immobilized on crosslinked gelatin were found to be substantially different from those of the suspended yeast. Batch fermentation experiments conducted in a gradientless reaction system allowed comparison of immobilized cell and suspended cell performance. The specific rate of ethanol production by the immobilized cell was 40–50% greater than for the suspended yeast. The immobilized cells consumed glucose twice as fast as the suspended cells, but their specific growth rate was reduced by 45%. Yields of biomass from the immobilized cell population were lower at one‐third the value for the suspended cells. Cellular composition was also affected by immobilization. Measurements of intracellular polysaccharide levels showed that the immobilized yeast stored larger quantities of reserve carbohydrates and contained more structural polysaccharide than did suspended cells. Flow cytometry was used to obtain. DNA, RNA, and protein frequency functions for immobilized and suspended cell populations. These data showed that the immobilized cells have higher ploidy than cells in suspension. The observed changes in immobilized cell metabolism and composition may have arisen from disturbance to the yeast cell cycle by the cell attachment, causing alterations in the normal pattern of yeast bud development, DNA replication, and synthesis of cell wall components.
Biomass yields and energetic yields of oleaginous yeasts in batch culture
Authors: Pan Jae G. , Rhee Joon S. 
Published: December 2004

AbstractThis article provides the analysis on biomass yields and energetic yields of the oleaginous yeasts. The biomass yields of the oleaginous yeasts are consistently lower than nonoleaginous microorganisms, whereas their energetic yields are higher. Data inconsistencies of literature are explained by the variation of energy contents of oleaginous yeasts.
Spore production of Penicillium roqueforti by solid state fermentation: Stoichiometry, growth and sporulation behavior
Authors: Desfarges Chantal , Larroche Christian , Gros Jean‐Bernard 
Published: December 2004

AbstractThe development of Penicillium roqueforti on buckwheat seeds proceeds roughly into four steps, involving a lag phase and three growth phases. First, it appears as a spore germination and external colonization of the grains by the mycelium. Then, mainly external sporulation and internal colonization of the seeds occur and finally internal sporulation takes place. The Stoichiometry of the growth and the sporulation is established. Kinetic experiments performed in a fixed bed reactor show that the growth of the microorganism (biomass production) may be estimated by the protein content of the medium. This growth occurs with a very low μmax value close to 0.030 h−1. The chitin content of the medium is an indicator of the sporulation, just as the metabolic liquor (mainly water) produced during the course of a cultivation. The values of the observed respiratory quotient are close to those predicted by stoichiometry.
Anaerobic saccharolytic bacterial adhesion to raw starch granules
Authors: Wang Hsi‐Hua , Chiou Tsyy‐Wen , Hsu Jyh‐Ping 
Published: December 2004

AbstractThe experiment of bacteria adhesion onto starch granules is conducted. It is found that anaerobic saccharolytic bacteria have the highest adhesion ability in their growth and initial stage of stationary phase. Starch granules with a low crystallinity, low bulk density, and high water‐holding capacity have a high adhesion capacity. The optimum temperature for both bacterial growth and their adhesion is 30°C. The optimum pH for the bacterial adhesion range from 5.0 to 6.5. Anaerobic conditions cause an appreciable decrease in percentage of adhesion. The percentage of adhesion is not sensitive to the type of soluble saccharide on which bacteria were grown.
Air‐stripping effects on cell growth with volatile substrates
Authors: Singh Nona , Hill G. A. 
Published: December 2004

AbstractThe removal of substate molecules from aerobic microbial cultures is due to both consumption by microorganisms and stripping by the air stream. The air stripping component can be described by a constant parameter for low concentrations of volatile substrates. This air stripping parameter was found to have a value of 0.0033 h−1 for phenol molecules in a typical fermentation situation. The determination and inclusion of this constant is important for modeling microbial growth. For Pseudomonas putida growing on phenol, it is shown that air stripping is responsible for all of the original decline in phenol concentration. Further, the kinetic inhibition constant is sensitive to both the value of the air stripping parameter and the value of the initial concentration of bacteria. The experimental data for Pseudomonas putida growing on phenol was fit by a non‐linear, least squares technique to isolate the inhibition constant between 100 and 600 ppm.
Optimal temperature control for batch beer fermentation
Authors: Gee Douglas A. , Ramirez W. Fred 
Published: December 2004

AbstractOptimal control theory was applied to the process of batch beer fermentation. The performance functional considered was a weighted sum of maximum ethanol production and minimum time. Calculations were based on the model of Engasser et al. modified to include temperature effects. Model parameters were determined from isothermal batch fermentations. The fermentor cooling duty was the single available control. Temperature state variable constraints as well as control variable constraints were considered. The optimal control law is shown to be bang‐bang control with the existence of a singular arc corresponding to isothermal operation at the maximum temperature constraint. An iterative algorithm is presented for computing appropriate switching times using a penalty‐function‐augmented performance functional.
Mathematical model of microporous hollow‐fiber membrane extractive fermentor
Authors: Fournier Ronald L. 
Published: December 2004

AbstractA mathematical model is presented for a microporous hollow‐fiber membrane extractive fermentor (HFEF). The model is based on the continuous flow of the aqueous nutrient phase and cells through the shell space of the fermentor where the fermentation reaction occurs. The product diffuses from the shell space through the hollow‐fiber membrane where it is continuously removed by solvent flowing concurrently through the fiber lumen. Results for ethanol production show that the HFEF has a volumetric productivity significantly higher than that possible using conventional methods. The model predicts the existence of an optimum volume fraction of hollow fibers in the fermentor that maximizes the total volumetric productivity. This optimum is the result of a classic trade‐off between the volume fraction of the fermentor required for fermentation and that required for efficient removal of the ethanol product to minimize product inhibition.
Transient characteristics of oxygen probes with significant liquid film effects
Authors: Linek V. , Vacek V. , Beneš P. , Sinkule J. 
Published: December 2004

AbstractVarious experimental procedures for the determination of transient characteristics with significant liquid film effects were tested. A comparison between transient characteristics obtained experimentally and those calculated from rational models indicates that all procedures but one give highly inconsistent results. Recalculation of transient characteristics with no liquid film (easily measured in the gas phase) to that with liquid film (occurring in viscous liquids) is recommended as well as the selected experimental procedure which yields consistent results in the situations where the steady‐state probe reading is decreased up to one‐half due to the liquid film.
Alginate as immobilization material. II: Determination of polyphenol contaminants by fluorescence spectroscopy, and evaluation of methods for their removal
Authors: Skjåk‐Bræk Gudmund , Murano Erminio , Paoletti Sergio 
Published: December 2004

AbstractAlginates, both commercial and laboratory made, are strongly fluorescent due to small amounts of polyphenolic materials. These contaminants can be detected by fluorescence spectroscopy in concentrations lower than 1 ppm. This technique has been used to measure polyphenols in a wide range of alginates and various procedures for preparation of biotechnological‐grade alginates have been evaluated.
Thermophilic semisolid anaerobic digestion of municipal refuses
Authors: Marique Ph. , Gilles A. , Edeline F. , Joassin L. 
Published: December 2004

AbstractComparison of both mesophilic (35°C) and thermophilic (55°C) anaerobic digestions of the organic fraction of municipal refuses in pilot digesters designed to process in a semisolid phase at total solids concentrations of ca. 25% shows that the average gas production is 20–25% higher in thermophilic conditions than in mesophilic conditions even for a retention time of 10 days. These results and the data recorded during long periods of experimentation indicate that the process allows to increase the net energy production and to improve the economical balance of an industrial plant.
Studies on growth and cardenolide production of Digitalis lanata tissue cultures
Authors: Tuominen U. , Toivonen L. , Kauppinen V. , Markkanen P. , Björk L. 
Published: December 2004

AbstractDigitalis lanata cell cultures grown as small undifferentiated aggregates in suspension culture can be redifferentiated into green embryos that produce cardenolides. The possibility of using a statistical (Box–Wilson) experimental design to study the effects of four different variables on growth, differentiation, and cardenolide production of D. lanata tissue cultures are investigated. The results of the analyses were processed by linear regression analysis. Mathematical models explaining the effects of the variables were developed. The concentration of maltose and the NO3−NH4+ ratio were found to be significant variables for both growth and cardenolide production. The size of the inoculum was also important.
Optimization of batch fermentor sterilization
Authors: Singh V. , Hensler W. , Fuchs R. 
Published: December 2004

AbstractThis article presents a calculation procedure useful for the optimization and scale up of batch sterilization cycles in large‐scale fermentors. This technique determines the sterilization temperature and hold‐time necessary to minimize nutrient damage in a specific fermentor. The method can also be used for “scaledown” experiments to eliminate sterilization conditions as a scale up parameter. A method for the systematic evaluation of different sterilization conditions on product yield is also presented. This procedure is useful in determining if scale up of sterilization conditions is important for a given process. The validity of the techniques presented are supported by data showing significant yield improvements in a 1.2 × 105 L antibiotic fermentation.