bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Computer‐aided noninterfering on‐line technique for monitoring oxygen‐transfer characteristics during fermentation processes
Authors: Spriet J. A. , Botterman J. , Buyser D. R. De , De Visscher P. L. , Vandamme E. J. 
Published: December 2004

AbstractThe role of computers in the monitoring and control of fermentation processes has increased steadfastly. The ultimate utility of the machines will not depend on the availability of online sensors but also on the availability of techniques that combine direct measurements, leading towards estimates of variable closely related to the microbial process or its control. In this article, a methodology for on‐line and noninterfering evaluation of the volumetric mass‐transfer coefficient Kla is developed. A detailed presentation of the procedure, called “the static method,” is given. Its feasibility is proved through implementation of the method on an antibiotic fermentation process. These experiments indicate that operator actions meant to modify the oxygen‐transfer conditions can be checked on‐line. The quantitative value of the static method is ascertained by comparing the experimental results with Kla estimates obtained with the “gassing‐out” method. A sensitivity analysis was carried out, revealing the need for temperature and pressure corrections and showing that the precision of the oxygen analyzer determines the precision of the static method.
The production of 6‐aminopenicillanic acid by a multistage tubular reactor packed with immobilized penicillin amidase
Authors: Park Jong M. , Choi Cha Y. , Seong Baik L. , Han Moon H. 
Published: December 2004

AbstractA theoretical model equation was derived to find the correlation between the conversion and the amount of immobilized penicillin amidase in column. The theoretical values of the conversion were predicted form this correlation and compared with experimental results. It was observed in a column reactor that the pH drop along the column path was linear versus the enzyme loading and that the enzyme activity was also linearly dependent on pH up to 8.0. In order to diminish the effect of pH drop, a continuous two‐stage plug‐flow reactor (PFR) with pH adjustment between the two columns was used was used in the experiments, and two‐ and three‐stage PFRs were simulated by computer. In the case of the two‐stage PFR, the maximum productivity was demonstrated experimentally and theoretically as well. when an equal amount of the immobilized enzyme was packed in both columns. It was also predicted in the tree‐stage PFR system that the optimal distributions of enzyme loading in three columns were found to be 1:1:1. It was demonstrated that the increased number of reactors in series could enhance the level of the maximum productivity with a given amount of enzyme loading.
Use of chemically modified activated carbon as a support for immobilized enzymes
Authors: Osborn James A. , Ianniello Robert M. , Wieck Henry J. , Decker Thomas F. , Gordan Susan L. , Yacynych Alexender M. 
Published: December 2004

AbstractLoading and activity assays of the enzymes α‐chymotrypsin, α‐chymotrypsinogen, and glucose oxidase covalently bound to an activated carbon support are presented. The activated carbon support material was pretreated using either a radio‐frequency oxygen plasma or an electrochemical oxidation to maximize the enzyme attachment. Cyanuric chloride or water‐soluble carbodiimide linking reactions were used to covalently attach the enzymes to the carbon support. Discussion of the relative merits of each reaction scheme is presented.
Farm‐scale production of fuel ethanol and wet grain from corn in a batch process
Authors: Westby Carl A. , Gibbons William R. 
Published: December 2004

AbstractThe batch production of fuel grade ethanol and distillers' wet grain (wet solids) in a farm‐scale process (1240–15,580 L/batch) is described. The employs yeast fermentation of amylase‐treated corn mash and a two‐stage distillation. Primary emphasis in this study was on the cooking, fermentation, and centrifugation steps. Without recycling, fermentation of the mash yield beers with 10.0–10.5% ethanol. Recycling of stillage supernatant at full, 75, or 50% strengths produced enriched mashes that after 48‐h fermentation yielded beers with 5–;14% more ethanol. Recycling twice with full‐strength supernatant at pH 7.0 increased the ethanol yield in the final beer 16.5%; however, the time to complete the final fermentation was extended form 48 to 72 h and salt buildup occurred. By recycling at pH 5.4, it was possible to avoid rapids salt buildup and obtain beers with 10.3–10.5% ethanol. Recycling resulted in increased levels of glucose, starch, crude protein, and fat in the beer and a reduced moisture content while the wet solids showed an increased starch content. Centrifugation after cooking or fermentation yield in the subsequently produced beer. Fermentation of a volume‐resorted mash supernatant gave a beer with only 9.25% ethanol. Mash wet solids varied somewhat chemically from beer and stillage solids. An economic and energy balance analysis of various modes of plant operation are provided and plant considerations are suggested.
Immobilization of yeast cells containing β‐galactosidase
Authors: Banerjee Mita , Chakrabarty Aloka , Majumdar S. K. 
Published: December 2004

AbstractCultural conditions optimum for β‐galactosidase production by Saccharomyces anamensis are pH 4.5, temperature 26 ± 2°C, and 30 h of incubation period. Addition of lactose at 24 h fermentation greatly increase the level of enzyme. Optimum pHl, temperature, pH stability, and thermostability of yeast β‐galactosidase are negligibly affected by immobilization. The Km values of enzyme in the native and immobilized cells are 102mM and 148mM, respectively. Glucose noncompetitively inhibits the enzyme activity. Addition of substances such as dithioerythritol, glutathione, and bovine serum albumin to the native cell during assay procedure and immobilized cell prior to immobilization have stimulatory effects on enzyme activity. Metal ions like Ca2+, Mg2+ enhance the β‐galactosidase activity for both intact and bound cells. Immobilized cells retain 68.6% of the β‐galactosidase activity of intact cells and there is no significant loss of activity on storage at 4°C for 28 days.
Process optimization of a continuous airlift tower‐loop reactor
Authors: Luttmann R. , Thoma M. , Buchholz H. , Lehmann J. , Schügerl K. 
Published: December 2004

AbstractBased on the experimental investigations with H. polymorpha and Methylomonas M 15 in bench‐scale airlift tower‐loop reactors, a general distributed parameter model was developed and used to simulate to cultivation process in a 40‐m‐high production reactor. This general model was simplified with regard to the gas phase and loop balances and was employed to optimize cell productivity and/or profit in a 20‐m‐high pilot‐plant airlift tower‐loop reactor. Maximum cell productivity always occurs in the oxygen‐transfer‐limited growth range. In case of a high “penalty factor” for nonconsumed substrate, maximum profit is attained at the boundary between substrate and oxygen‐transfer‐limited growth. Oxygen‐transfer limitation exists in the lower half of the tower, whereas in the upper half, substrate limitation prevails. The longitudinal dissolved oxygen concentration passes a minimum in this case as has been determined experimentally in the bench‐scale column. The simulation results agree fairly well with the data measured in the pilot plant.
Dynamic simulator for anaerobic digestion processes
Authors: Kleinstreuer C. , Poweigha T. 
Published: December 2004

AbstractA transient, two‐culture model simulating methane production from biomass has been developed. The simulator, based partially on the work by Andrews and McCarty, is capable of calculating the hydrolysis products of several common organic materials, accommodating various substrate feeding modes, and simulating the transient physico‐biochemical transport and conversion processes occurring in the biological, liquid, and gaseous phases of a well‐mixed reactor. The mathematical representation of this bioconversion system consists of a set of 11 coupled, nonlinear first‐order rate equations based on the principles of mass conservation and biochemical reaction kinetics. The model can be used in conjunction with laboratory investigations and as a simulator for evaluating process control strategies and cost developments.
Continuous culture of the ciliate Tetrahymena pyriformis on Escherichia coli
Authors: Swift Steven T. , Najita Irene Y. , Ohtaguchi Kazuhisa , Fredrickson A. G. 
Published: December 2004

AbstractThe ciliated protozoan Tetrahymena pyriformis was grown in a chemostat fed with a culture of Escherichia coli overflowing from another chemostat. Densities of the protozoan and bacterial populations, mean volume of protozoan cells, yields of protozoan volumes and numbers, and filtering rates of protozoans per cell and per unit volume of biomaterial were determined at five different dilution rates. The data obtained supplement other data already available for the popular test organism T. pyriformis, and they are also comparable with data available for related ciliates.
Kinetics of biodegradation of 2,4‐dichlorophenoxyacetate in the presence of glucose
Authors: Papanastasiou A. C. , Maier W. J. 
Published: December 2004

AbstractBiodegradation of 2,4‐dichlorophenoxyacetate (2,4‐D) and glucose were studied using a 2,4‐D acclimated culture. Biodegradation of glucose by the 2,4‐D preacclimated culture follows the typical Monod kinetics after a 20‐h lag period in the presence or absence of 2,4‐D. Biodegradation of 2,4‐D by the same culture follows Andrew's “substrate inhibition” model. When both glucose and 2,4‐D are available, mutual inhibition is observed. However, the effect on 2,4‐D is masked by the fact that larger concentrations of active biomass are produced when glucose is available. This kind of concurrent utilization and interaction results in a substantial reduction of the mean cell residence time in a continuous flow system. It also extends the area of stability of the process into higher dilution rates as well as into higher influent concentrations.
Stability of glucose oxidase and catalase adsorbed on variously activated 13X zeolite
Authors: Pifferi P. G. , Vaccari A. , Ricci G. , Poli G. , Ruggeri O. 
Published: December 2004

AbstractThe use of 13X zeolite (0.1‐0.4‐mm granules), treated with 2N and 0.01N HCI, 0.01M citric acid, 0.1M citric‐phosphate buffer (pH 3.6), and in untreated form to adsorb glucose oxidase of fungal origin and microbial catalase was examined. Physicochemical analysis of the support demonstrated that its crystalline structure, greatly altered by the HCl and buffer, could be partially maintained with citric acid. The specific adsorption of the enzymes increased with decreasing pH and proved to be considerable for all the supports. The stability with storage at 25°C is strictly correlated with the titrable acidity of the activated zeolite expressed as meq NaOH/g and with pH value of the activation solution. It proved to be lower than 55 h for both enzymes if adsorbed on zeolite treated with 2N HCl, and 15‐fold and 30‐fold higher for glucose oxidase and catalase adsorbed, respectively, on zeolite treated with the 0.1M citric‐phosphate buffer and 0.01M citric acid. The specific adsorption of glucose oxidase and catalase was, respectively, 1840 U/g at pH 3.0 and 6910 U/g at pH 5.0. Their half‐life at 25°C with storage at pH 3.5 for the former and at pH 5.0 for the latter was 800 and 1560 h vs. 40 and 110 h for the corresponding free enzymes.
Continuous glutamate production using an immobilized whole‐cell system
Authors: Kim H. S. , Ryu Dewey D. Y. 
Published: December 2004

AbstractFor the purpose of saving the energy and raw materials required in glutamate fermentation, an immobilized whole‐cell system was prepared and its performance in a continuous reactor system was evaluated. Corynebacterium glutamicum (a mutant strain of ATCC 13058) whole cell was immobilized in K‐carrageenan matrix and the gel structure was strengthened by treatment with a hardening agent. The effective diffusivities of carrageenan gel for glucose and oxygen were found to decrease significantly with an increase in carrageenan concentration, while the gel strength showed an increasing trend. Based on the physical and chemical properties of carrageenan gel, the immobilization method was improved and the operation of the continuous reactor system was partially optimized. In an air‐stirred fermentor, the continuous production of glutamate was carried out. The effect of the dilution rate on glutamate production and operational stability were investigated. The performance of the continuous whole‐cell reactor system was evaluated by measuring glutamate productivity for a period of 30 days; it was found to be far superior to the performance of conventional batch reactor systems using free cells.
Continuous conversion of D‐xylose to ethanol by immobilized pachysolen tannophilus
Authors: Slininger P. J. , Bothast R. J. , Black L. T. , McGhee J. E. 
Published: December 2004

AbstractThe yeast Pachysolen tannophilus was entrapped in calcium alginate beads to ferment D‐xylose on a continous basis in the presence of high cell densities. Experimental operating variables included the feed D‐xylose concentration, the dilution rate, and the fermentor biomass concentration. Under favorable operating conditions, cultures retained at least 50% of their initial productivity after 26 days of operation. The specific ehanol production rate was dependent on the substrate level in the fermentor, passing through an optimum when the D‐xylose concentration was between 28 and 35 g/L. Consequently, reactor productivity increased with dilution rate and feed D‐xylose concentration until a maximum was reached. The ethanol content of the effluent always decreased with increasing dilution rate, but excessive dilution rates diminished the ethanol content without increasing productivity. Unlike production rate, ethanol yield declined monotonically from 0.35 g/g as the fermentor substrate concentration increased. The yield was 69% of that theoretically possible when the D‐xylose concentration was near zero, as opposed to 42% when it was in the range supporting the optimum specific rate of ethanol production. As long as D‐xylose was supplied to cells faster than they could consume it, productivity increased with the mass of cells immobilized. The effectiveness factor associated with the calcium alginte beads used in this system was 0.4, indicating that only 40% of the entrapped biomass was effective in converting D‐xylose to ethanol because of diffusion limitations.
Modeling of percolation process in hemicellulose hydrolysis
Authors: Cahela D. R. , Lee Y. Y. , Chambers R. P. 
Published: December 2004

AbstractA mathematical model was developed for a percolation reactor in connection with consecutive first‐order reactions. The model was designed to simulated acid‐catalyzed cellulose or hemicellulose hydrolysis. The modeling process resulted in an analytically derived reactor equation, including mass‐transfer effects, which was found to be useful in process desing and reactor optimization. The modedl was verified by experimental data obtained from hemicellulose hydrolysis.
Conversion of pentoses by yeasts
Authors: Gong Cheng‐Shung , Claypool Tanya A. , McCracken Linda D. , Maun Christine M. , Ueng Pear P. , Tsao George T. 
Published: December 2004

AbstractThe utilization and conversion of D‐xylose, D‐xylulose, L‐arabinose, and xylitol by yeast strains have been investigated with the following results: (1) The majority of yeasts tested utilize D‐xylose and produce polyols, ethanol, and organic acids. The type and amount of products formed varies with the yeast strains used. The most commonly detected product is xylitol. (2)The majority of yeasts tested utilize D‐xylulose aerobically and fermentatively to produce ethanol, xylitol, D‐arabitol, and organic acids. The type and amount of products varies depending upon the yeast strains used. (3) Xylitol is a poor carbon and energy source for most yeasts tested. Some yeast strains produce small amounts of ethanol from xylitol. (4) Most yeast strains utilize L‐arabinose, and L‐arabitol is the common product. Small amounts of ethanol are also produced by some yeast strains. (5) Of the four substrates examined, D‐xylulose was the perferred substrate, followed by D‐xylose, L‐arabinose, and xylitol. (6) Mutant yeast strains that exhibit different metabolic product patterns can be induced and isolated from Candida sp. Saccharomyces cerevisiae, and other yeasts. These mutant strains can be used for ethanol production from D‐xylose as well as for the study of metabolic regulation of pentose utilization in yeasts.
Effects of mass‐transfer resistance on apparent stability and performance of fixed‐bed immobilized enzyme reactors: Theory and experiments with immobilized invertase
Authors: Ooshima Hiroshi , Harano Yoshio 
Published: December 2004

AbstractTaking the hydrolysis of sucrose by invertase immobilized on anion‐exchange resin as an example, the effects of mass‐transfer resistance on the apparent stability of immobilized enzyme (IME) and the optimal policy for an IME reaction in a fixed‐bed reactor have been studied theoretically and experimentally. The following results were obtained: (1) The effect of mass‐transfer resistance on the effective deactivation rate of IME is summarized in two parameters concerning the intraparticle diffusion αp and the interparticle αf. (2) At a constant processed amount of raw materials, there exists an optimal flow rate of reaction fluid to enhance the reactor performance while the mass‐transfer resistance shifts the optimal point. (3) The intrinsic deactivation rate of IME has been estimated from the relationship between the fractional conversion at the reactor outlet and the operation time.
Characterization of the two‐phase systems in airlift tower–loop bioreactors during the cultivation of E. coli
Authors: Lippert J. , Adler I. , Meyer H. D. , Lübbert A. , Schügerl K. 
Published: December 2004

AbstractDuring the cultivation of E. coli in an airlift tower–loop bioreactor, the following properties were measured: transverse profiles of Sauter bubble diameter, dS; local relative gas holdup, EG; bubble rise velocity, uBS; local mean velocity, ū turbulence intensity, u′; macrotime scale, TEL; dissipation time scale, τE; power spectrum, E(n); and energy dissipation spectrum D(n) at different distances from the aerator. The influence, distance from the aerator, absence and/or presnece of cells, and batch and/or continuous‐culture operation on the behavior of the two‐phase system are discussed on the basis of these properties.
Factors affecting cell attachment, spreading, and growth on derivatized microcarriers. I. Establishment of working system and effect of the type of the amino‐charged groups
Authors: Reuveny Shaul , Mizrahi Avshalom , Kotler Moshe , Freeman Amihay 
Published: December 2004

AbstractA working system for studying the effects of factors involved in the chemical nature of microcarriers on cell attachment, spreading, and growth was established. The system is based on polyacrylamide beads, prepared by the emulsion polymerization technique. Sieved beads of desirable mean diameter were derivatized to generate controlled amounts of primary and tertiary amino groups. These microcarriers were used for the propagation of four different cell strains: BHK, MDCK, CEF, and MRC‐5. It was found that BHK cells attach and spread significantly faster on primary amino‐derivatized beads than those with tertiary amino groups, and at a lower degree of charging. Cell yields of MDCK cells (with pronounced epithelial morphology) propagated on primary amino‐derivatized beads were higher than that obtained for the tertiary amino‐derivatized microcarriers. On the other hand, CEF and MRC‐5 cells (with pronounced fibroblast morphology) achieved higher cell yields on the tertiary amino‐derivatized microcarriers.
Ethanol fermentation with cell recycling: Computer simulation
Authors: Lee J. M. , Pollard J. F. , Coulman G. A. 
Published: December 2004

AbstractA mathematical model for glucose‐to‐ethanol fermentation at high yeast cell concentrations was developed. The feasibility of improving fermenter productivity over that of a conventional continuous‐stirred‐tank fermenter by using multiple stage reactors and yeast cell recycling was predicted by computer simulation. The optimum size distribution for multistage fermentors was obtained for different glucose feedstream concentrations and different glucose conversion levels. Productivity increases over a single‐stage reactor ranged from 1.2–2.0 times. The use of yeast cell recycling to increase cell concentration and productivity increases of over 4.0 times that of a system without recycling.
Anodic reactions in microbial fuel cells
Authors: Bennetto H. Peter , Stirling John L. , Tanaka Kazuko , Vega Carmen A. 
Published: December 2004

AbstractPotentiometric and amperometric measurements were made with microbial fuel cells containing E. coli or yeast as the anodic reducing agent and glucose as the oxidizable substrate. The catalytic effects of thionine and resorufin on the anode reaction were investigated. Results on the potentiometry, polarization, and coulombic output of the cells support a mediator‐coupled mechanism for the transfer of electrons from the organism to the electrode in preference to a mechanism of “direct” electrochemical oxidation of glucose or its degradation products. Experiments with 14C‐labeled glucose show that when a microbial fuel cell produces a current under load, exogenous glucose is metabolized to produce 14CO2. The Coulombic yields of the cells indicate a high degree of energy conversion in these systems.
Growth and anthocyanin accumulation rates of carrot suspension cultures grown with excess nutrients after semicontinuous culture with different limiting nutrients at several dilution rates, pHs, and temperatures
Authors: Dougall D. K. , LaBrake S. , Whitten G. H. 
Published: December 2004

AbstractWhen carrot cell cultures, after growth in semicontinuous culture, were transferred to media containing excess nutrients, they grew at different rates. The growth rates were generally higher after semicontinuous culture at higher dilution rates. There appears to be a limit on dilution rate above which growth rate does not increase. These changes were also displayed by clones from the parental culture. The possibility that these changes in growth rate reflect a need for the cultures to adapt to their new conditions is discussed. The growth rates of the cultures is markedly increased at 25°C compared with 22°C with little further increase at 28°C. Growth rate is altered by less than 20% when pH is changed from 4.5 to either 5.5 or 4.2. The rates of anthocyanin accumulation by the cultures were similar under all conditions tested except at 22°C. They were larger than the rates of dry weight accumulation. In contrast, the amounts of anthocyanin accumulated in the clones and in the parental cultures grown at pH 5.5 instead of pH 4.5 were very different. The observations were interpreted as showing that the clones differ in the rate of metabolism but not in the rate of synthesis of anthocyanins and that at pH 5.5 the rate of metabolism of anthocyanins but not the rate of synthesis is higher than it is at pH 4.5. The use of semicontinuous cultures as a source of inoculum for batch cultures rather than as a source of biomass for extraction of chemicals is discussed.