ISSN:0006-3592    

DOI:10.1002/bit.260390102

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

年代:1992

数据来源: WILEY

摘要:

AbstractAn examination is made of five methods for obtaining values of the enthalpy of formation of a unit mass of livingEscherichia coliK‐12 cells. The values obtained by these methods ranged from −88.95 kJ to −99.55 kJ, the gross average being 96.01 kJ, per unit carbon formula weight equivalent of living, hydrated cells. Although theoretically the growth of this organism in a microcalorimeter should provide the best value, the value obtained by this method (−88.95 kJ per UCFW equivalent) is not in close agreement with those of the other four methods, the values from which form a cluster averaging −97.8 ± 1.0 kJ (−23.4 ± 0.2 kcal)/UCFW equivalent. Calculations using this value indicate that the enthalpy change accompanying anabolism (as this is represented) is zero, or very nearly so, and that the heat of growth is that from cat

ISSN:0006-3592    

DOI:10.1002/bit.260390103

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

年代:1992

数据来源: WILEY

摘要:

AbstractFront‐surface detection of emission from fluorophores in the presence and absence of light‐scattering particles was contrasted to right‐angle and wave‐guide detection. We found that front‐surface detection was the least prone to the reabsorption, inner‐filtering, and scattering effects that can plague fluorescent measurements. Front‐surface detection was thus used to assess the use of protein and ANS fluorescence as a means of monitoring events in bacterial fermentations. Protein fluorescence appeared to track well changes in optical density during balanced growth. However, during the lag associated with diauxic growth and after exposure to ampicillin, protein fluorescence became decoupled from cellular growth in a manner consistent with prior observations and the known effect of ampicillin on cells. ANS proved to be nontoxic and capable of reporting the occurrence of protein release from cells. The spectral shifts of tryptophan indicated that the incorporation of tryptophan into cellular protein can

ISSN:0006-3592    

DOI:10.1002/bit.260390104

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe extraction of protein using reversed micelles was investigated in relation to the amount of solubilizing water in the reversed micellar organic phase. The minimal concentration of amphiphilic molecule di‐2‐ethylhexyl sodium sulfosuccinate (C20H37O7Na) (AOT) required for 100% cytochromecextraction was recognized. This critical AOT concentration increased with protein concentration in the aqueous phase. On this minimal AOT condition, the molar ratio of solubilizing water to extracted protein was found to be a constant of 3500 underCKCI= 1.0 × 102mol · m−3in this system. This ratio means the hydrophillic surroundings required for extracting one protein molecule into the micellar organic phase under the suitable pH and salt concentration for the forward extraction. In this regard, AOT molecules seemed to take the part of water solubilizing agent in the reversed micellar extraction. This role of AOT is important to extract protein under the suitable pH and salt concentration. The amount of solubilizing water in the protein‐containing system was larger than in the protein‐free system. This difference shows that the water molecules accompany the extracted protein into the reversed micellar organic phase at constant ratio 2200 underCKCI= 1.0 × 102mol · m−3, i.e., accompanying water molecules per one extracted protein. The minimal AOT concentration increased with ionic strength. On this minimal AOT condition, the molar ratio of solubilizing water to extracted protein also increased with ionic strength, so that in higher ionic strength, more solubilizing water was required. Then more AOT was required to provide the hydrophillic surroundings for protein. The pH affected the minimal AOT concentration required for 100% pro

ISSN:0006-3592    

DOI:10.1002/bit.260390105

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

年代:1992

数据来源: WILEY

摘要:

AbstractProtein production of mammalian cells has been promoted by applying a small constant potential to the surface of an electrode on which cells are cultured. Human carcinoma line of MKN45 cells were cultured on the surface of a platinum‐coated plastic plate electrode. Low d.c. voltage of constant potential was applied to the electrode during 4‐day culture to modulate the production of carcinoembryonic antigen (CEA). The amounts of both secreted and membrane‐bound CEA were dependent on the applied potential during culture. Secreted CEA was more than twice in amount in the potential range from 0.2 V to 0.6 V vs. Ag/Agcl as compared with that of normal culture. In the potential range, CEA was also increased in membrane‐bound form. The potential‐controlled cell culture may have an enhanced effect on protein p

ISSN:0006-3592    

DOI:10.1002/bit.260390106

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

年代:1992

数据来源: WILEY

摘要:

AbstractFor the control of bioprocesses, a priori knowledge exists which cannot be readily incorporated as a mathematical model but which can be represented by language‐based rules, such as “IF/THEN” conditions. This knowledge is usually implemented via a process operator for the automation of the fermentation. A knowledge‐based system has been developed which can use this kind of knowledge and which is complemented by algorithmic systems, such as statistical analyses and mathematical modeling, for the supervision and control of a bioprocess. In this article, a description of this system is presented. Furthermore, the following features of the system are discussed in detail which are especially important for the development of real‐time, on‐line, knowledge‐based systems: the representation of time‐dependent knowledge; processing of imprecise, uncertain, and incomplete knowledge; the combination of shallow reasoning with model‐based reasoning; informing the bioprocess operator about the inferences and decisions; the demands of the diversity of the knowledge handling; performance; and maintenance and extens

ISSN:0006-3592    

DOI:10.1002/bit.260390107

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

年代:1992

数据来源: WILEY

摘要:

AbstractGrowth ofStreptomyces tendaewas investigated in submerged culture. Images of several mycelia were analyzed by means of an image‐processing system. The studies revealed that tip growth angles and branching outgrowth angles could be regarded as normally distributed. Based on these results, a random model for directional growth of hyphal tips as well as directional growth of branches is proposed. This model shows curved elongation of hyphal tips, so that the morphological development of a mycelium up to the formation of a pellet is predicted, similar to that observed in natur

ISSN:0006-3592    

DOI:10.1002/bit.260390108

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

年代:1992

数据来源: WILEY

摘要:

AbstractA mathematical model for apical growth, septation, and branching of mycelial microorganisms is presented. The model consists of two parts: the determinstic part of the model is based on fundamental cellular and physical mechanisms; it represents the kinetics for growth of hyphal tips and septation of apical as well as intercalary compartments. In regard to random occurrences of hyphal growth and branching, the stochastic part deals with branching processes, tip growth directions, and outgrowth orientations of branches. The model can explain the morphological development of mycelia up to the formation of pellets. The results, as predicted by the model, correspond very closely to those observed in experiments. In addition, some unmeasured states can be ascertained, such as the distribution functions of hyphal length (biomass) and tips along pellet radii.

ISSN:0006-3592    

DOI:10.1002/bit.260390109

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

年代:1992

数据来源: WILEY

摘要:

AbstractFermentation patterns ofEscherichia coliHB101 carrying plasmids expressing cloned genes ofZymomonas mobilispyruvate decarboxylase (PDC) and alcohol dehydrogenase li (ADH) were determined in glucose‐limited complex medium in pH‐controlled anaerobic batch cultivations. Time profiles of glucose, dry cell weight, succinate, formate, acetate, and ethanol were determined, as were the activities of ADH and PDC. Fluxes through the central carbon pathways were calculated for each construct utilizing exponential phase data on extracellular components and assuming quasi‐steady state for intermediate metabolites. Overall biomass yields were greatest for cells expressing both PDC and ADH activities. Yields of carbon catabolite end products were similar for all PDC‐expressing strains and different from those for other strains. Relative to its glucose uptake rate, the strain with greatest PDC and ADH activities produces formate and acetate more slowly and ethanol more rapidly than other strains. Strong influences of plasmid presence and metabolic coupling complicate detailed interpretations of t

ISSN:0006-3592    

DOI:10.1002/bit.260390110

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetics of the bioleaching of ZnS concentrate byThiobacillus ferrooxidanswas studied in a well‐mixed batch reactor. Experimental studies were made at 30°C and pH 2.2 on adsorption of the bacteria to the mineral, ferric iron leaching, and bacterial leaching. The adsorption rate of the bacteria was fairly rapid in comparison with the bioleaching rate, indicating that the bacterial adsorption is at equilibrium during the leaching process. The adsorption equilibrium data were correlated by the Langmuir isotherm, which is a useful means for predicting the number of bacteria adsorbed on the mineral surface. The rate of chemical leaching varied with the concentration of ferric iron, and the first‐order reaction rate constant was determined. Bioleaching in an iron‐containing medium was found to take place by both direct bacterial attack on the sulfide mineral and indirect attack via ferric iron. In this case, the ferric iron was formed from the reaction product (ferrous iron) through the biological oxidation reaction. To develop rate expressions for the kinetics of bacterial growth and zinc leaching, the two bacterial actions were considered. The key parameters appearing in the rate equations, the growth yield and specific growth rate of adsorbed bacteria, were evaluated by curve fitting using the experimental data. This kinetic model allowed us to predict the liquid‐phase concentrations of the leached zinc and free cells during the batch bioleaching

ISSN:0006-3592    

DOI:10.1002/bit.260390111

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

年代:1992

数据来源: WILEY