摘要:

AbstractIn 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 atallnutrient concentrations, if that same species is sufficientlylessmotile than the other species. (3) In fact, the species with the smaller maximum specific growth rate may grow to alargerpopulation than the other. (4) The possibility of coexistence can be decided essentially from the results for single population g

ISSN:0006-3592    

DOI:10.1002/bit.260250902

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractDistiller's wet grain (DWG) and 95% ethanol were produced from corn in a farm‐scale process involving batch cooking–fermentation and continuous distillation–centrifugation. The energy balance was 2.26 and the cost was $1.86/gal (1981 cost). To improve the energy balance and reduce costs, various modifications were made in the plant. The first change, back‐end (after liquefaction) serial recycling of stillage supernatant at 20 and 40% strengths, produced beers with 0.2 and 0.4% (v/v) more ethanol, respectively, than without recycling. This increased the energy balance by 0.22–0.43 units and reduced costs by $0.07–$0.10/gal. The DWGs from back‐end recycling had increased fat. The second change, increasing the starch content from 17–19% to 27.5%, increased the ethanol in the beer from 10.5–14.9% at a cost saving of $0.41/gal. The energy balance increased by 1.08 units. No significant change was seen in DWG composition. The third change, using continuous cascade rather than batch fermentation, permitted batch‐levels of ethanol (10%) in the beer but only at low dilution rates. Both the cost and energy balance were decreased slightly. The DWG composition remained constant. The last change, replacing part of the corn and all of the tap water in the mash with whole whey and usingKluyveromyces fragilisinstead ofSaccharomyces cerevisiaeduring fermentation, resulted in an energy balance increase of 0.16 units and a $0.27/gal cost reduction. Here, 10% ethanolic beers were produced and the DWGs showed increased protein and fat. Recommendations for farm‐scal

ISSN:0006-3592    

DOI:10.1002/bit.260250903

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe need for the determination of the free energy of formation of biomass in bioreactor second law balances is well established. A statistical mechanical method for the calculation of the free energy of formation ofE. colibiomass is introduced. In this method, biomass is modelled to consist of a system of biopolymer networks. The partition function of this system is proposed to consist of acoustic and optical modes of vibration. Acoustic modes are described by Tarasov's model, the parameters of which are evaluated with the aid of low‐temperature calorimetric data for the crystalline protein bovine chymotrypsinogen A. The optical modes are described by considering the low‐temperature thermodynamic properties of biological monomer crystals such as amino acid crystals. Upper and lower bounds are placed on the entropy to establish the maximum error associated with the statistical method. The upper bound is determined by endowing the monomers in biomass with ideal gas properties. The lower bound is obtained by limiting the monomers to complete immobility. On this basis, the free energy of formation is fixed to within 10%. Proposals are made with regard to experimental verification of the calculated value and extension of the calculation to other types of biom

ISSN:0006-3592    

DOI:10.1002/bit.260250904

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractActivated sludge treatment of a pentachlorophenol (PCP)‐containing synthetic waste was examined. With a waste containing some sugars, and 40–120 mg/L PCP, laboratory activated sludge required about seven days for acclimation. However, the prior addition of a quasipure culture of PCP‐metabolizingArthrobacterresulted in immediate acclimation. Even with acclimated sludge, however, the system was upset for two days by a simple step change from 40 to 120 mg/L of PCP. The stability of the system to such a shock load was considerably improved when a chemostat culture of the PCP‐metabolizingArthrobacterwas fed slowly into the mixed liquor. Kinetic models were developed to describe the dynamic response of the system in terms of growth parameters, hydraulic detention time, sludge age, and bleed‐in rate from the

ISSN:0006-3592    

DOI:10.1002/bit.260250905

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractA systematic method is presented which is capable of both detecting the presence of grossly biased measurement errors and locating the source of these errors in a bioreactor through statistical hypothesis testing. Equality constraints derived from material and energy balances are employed for the detection of data inconsistencies and for the subsequent identification of the suspect measurements by a process of data analysis and rectification. Maximum likelihood techniques are applied to the estimation of the states and parameters of the bioreactor after the suspect measurements have been eliminated. The level of significance is specified by the experimenter while the measurments are assumed to be randomly, normally distributed with zero mean and known variances. Two different approaches of data analysis, batchwise and sequential, that lead to a consistent set of adjustments on the experimental values, are discussed. Several examples based on the fermentation data taken from literature sources are presented to demonstrate the utility of the proposed method, and one set of data is solved numerically to illustrate the computational aspect of the algorithm.

ISSN:0006-3592    

DOI:10.1002/bit.260250906

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractA new immobilization technique has been developed. It involves immobilizing enzymes on a porous polytetrafluoroethylene membrane with a nonporous polyurethane coat by the use of an electrostatic force, i.e. the Coulomb force. The immobilized enzyme can be recovered by supplying a reversed electrical potential. The reaction characteristics of the immobilized amyloglucosidase were studied using maltose as a substrate. The Michaelis constant becomes larger than that of the native enzyme, and depends on the electrical potential gradient in the solution.

ISSN:0006-3592    

DOI:10.1002/bit.260250907

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe contribution of the reversible thermal unfolding of an enzyme toward the overall irreversible thermoinactivation process has been examined both theoretically and experimentally. Using bovine pancreatic ribonuclease as a model, we have studied the effect of such variables as pH and salts both on the equilibrium constant of reversible denaturation and on the rate constant of the overall irreversible process. It has been demonstrated that at temperatures where a significant fraction of the enzyme molecules are in the native conformation, there is a correlation between the enzyme thermostabilities with respect to the reversible and irreversible inactivations: greater stability against the former is accompanied by greater stability against the latter. On the other hand, at very high temperatures (where essentially all of the enzyme molecules are unfolded), such a correlation does not exist. These findings are considered in terms of a kinetic model for irreversible enzyme thermoinactivation, and the implications of the derived relationship are discussed.

ISSN:0006-3592    

DOI:10.1002/bit.260250908

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractWhole cells ofEscherichia colicontaining the enzyme penicillinamidohydrolase EC 3.5.1.11 were immobilized on the surface of modified macroporous copolymers of glycidylmethacrylate with ethylenedimethacrylate and of copolymers of methacrylaldehyde (MA) with divinylbenzene (DVB) by means of glutaraldehyde. These polymeric carriers were modified before cell binding by using ammonia or polyamines, especially ethylenediamine and hexamethylenediamine (HMDA). The highest specific activity and the largest yield in cell immobilization were achieved with the macroporous copolymer of MA and DVB modified with HMDA. The material thus obtained was used in repeated conversions of benzylpenicillin to 6‐aminopenicillanic acid in a stirred batch reacto

ISSN:0006-3592    

DOI:10.1002/bit.260250909

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractIn this article, a mathematical model describing the kinetics of ethanol fermentation in a whole cell immobilized tubular fermentor is proposed. Experimental results show reasonable agreement with the proposed model. A procedure for treating the fermentation data for determining the ethanol inhibition constantsk1andk2is described. The ethanol productivity of the immobilized cell fermentor is compared with those of traditional fermentors. Experimental studies indicate that withSaccharomyces cerevisiae(NRRL Y132) culture, ethanol productivity in the range 21.2–83.7 g ethanol L−1h−1at ethanol concentration of 76–60 g/L can be achieved. This is comparable to or higher than those reported in the literature for yeast. The product yield factor of 0.5 g ethanol/g glucose was obtained. The immobilized cell fermentor does not show washout at dilution rates of 7 h−1and shows good stability over a 650‐h opera

ISSN:0006-3592    

DOI:10.1002/bit.260250910

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260250911

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY