摘要:

AbstractPrevious research has shown that dissolved carbon dioxide causes significant changes in submerged penicillin fermentations, such as stunted, swollen hyphae, increased branching, lower growth rates, and lower penicillin productivity. Influent carbon dioxide levels of 5 and 10% were shown through the use of autoradiography to cause an increase in chitin synthesis in submerged cultures ofPenicillium chrysogenum.At an influent 5% carbon dioxide level, chitin synthesis is ca. 100% greater in the subapical region ofP. chrysogenumhyphae than that of the control, in which there was no influent carbon dioxide. Influent carbon dioxide of 10% caused an increase of 200% in chitin synthesis, it is believed that the cell wall must be plasticized before branching can occur and that high amounts of dissolved carbon dioxide cause the cell to lose control of the plasticizing effect, thus the severe morphological changes occur.

ISSN:0006-3592    

DOI:10.1002/bit.260320103

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

年代:1988

数据来源: WILEY

摘要:

AbstractA membrane‐covered polarographic oxygen electrode was used to measure oxygen diffusion coefficients in aqueous polyelectrolyte solutions of xanthan gum, sodium alginate, and sodium carboxymethylcellulose (CMC). In sodium alginate solutions, dilute xanthan solutions, and solutions containing more than 0.3 wt % CMC, oxygen diffusion coefficients decrease with increasing polymer concentrations. Interestingly, in dilute CMC solutions and concentrate xanthan solutions containing more than 0.5 wt % xanthan gum, oxygen diffusion coefficients increase with increasing polymer concentrations, and values exceeding that in pure water are generally observe

ISSN:0006-3592    

DOI:10.1002/bit.260320104

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

年代:1988

数据来源: WILEY

摘要:

AbstractKinetics of protein solubilization during barley mashing with neutral proteinase were studied. By plotting the kinetics data in Foster–Niemann coordinates for barley concentration range of 10–30% linear relationships with high correlation coefficients (r⩾ 0. 999) were obtained. The slopes of straight lines were very close to corresponding reciprocal initial insoluble nitrogen concentrations. Barley proteolytic inhibitors affected the ordinate intercept; by their addition the values of ordinate intercept decreased. The data suggest that the modified Foster–Niemann equation can be proposed to interpret kinetics of insoluble barley protein degradation. The proteolytic activity decay was studied as well. The enzyme decay was faster in buffer solution than during barley mashing, but in both cases first‐order kinetics can be applied. A mathematical model describing protein solubilization and enzyme decay kinetics were developed. The results of computer simulation were in good agreement with experime

ISSN:0006-3592    

DOI:10.1002/bit.260320105

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe defined microbial cultures for methane generation from lactose were investigated. A mixed culture consisting of homolactic (Streptococcus lactis), homoacetic (Clostridium formicoaceticum), and acetate‐utilizing methanogenic (Methanococcus mazei) bacteria was used to convert lactose and whey permeate to methane at mesophilic temperatures (35–37°C) and a pH around 7.0. Lactose was first converted to lactic acid byS. lactis, then to acetic acid byC. formicoaceticum, and finally to methane and CO2byM. mazei.About 5.3 mol methane were obtained from each mole of lactose consumed, and the conversion of acetate to methane was the rate‐limiting step for this mixed‐culture ferm

ISSN:0006-3592    

DOI:10.1002/bit.260320106

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

年代:1988

数据来源: WILEY

摘要:

AbstractReduction in the activity and the concentration of the adsorbed enzyme are noted in the experimental data. Two alternative mechanisms, inactivation of the adsorbed enzyme and mass transfer of the enzyme from the bulk solution to the solution within the cellulose fibril where the cellulase is assumed to be inactive, are used to represent the decline in activity. The decline in concentration of the adsorbed enzyme is represented by a modest product inhibition and, more importantly, the assumption that the concentration of the adsorption sites is proportional to the square of the remaining substrate concentration. Measurements of both adsorbed enzyme and product concentration over time are used in determining parameter values. The model is applied to a series of experiments having a 10‐fold range of substrate concentration and to an experiment in which the product is removed continuously. For both deactivation mechanisms, a very good representation of product concentration (standard deviation 3.6%) is obtained over the full period (168 h) of hydrolysis; the representation of adsorbed enzyme is, however, less accurate (standard deviation 6.7–6.

ISSN:0006-3592    

DOI:10.1002/bit.260320107

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

年代:1988

数据来源: WILEY

摘要:

AbstractA cybernetic model to predict the low‐growth‐rate behavior of bacteria in mixed‐substrate environment is presented. Using only growth and maintenance parameters from single‐substrate experiments, the model accurately predicts the simultaneous substrate utilization and maintenance energy effects in constant fed‐batch cultures ofKlebsiella oxytoca. The robustness of the model was examined more rigorously by perturbing glucose‐limited fed‐batch cultures with additions of arabinose, xylose, and fructose. In all cases, reasonable agreement of the model prediction with the experimental data

ISSN:0006-3592    

DOI:10.1002/bit.260320108

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

年代:1988

数据来源: WILEY

摘要:

AbstractA method has been developed for measuring fermentation parameters such as dissolved oxygen, pH, and cell density that differs from traditional techniques that require electrodes and off‐line samples. Fluorescent indicators, each sensitive to a single variable, are dissolved directly into a fermentation broth. A fiber‐optic probe fluorimeter measures the fluorescence intensities that can then be correlated with parameter values. In addition, an integrated scatter scanning technique can be used to monitor cell densityin situ.Results have been obtained using simulated baker's yeast broth and during actual baker's yeast fermentati

ISSN:0006-3592    

DOI:10.1002/bit.260320109

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

年代:1988

数据来源: WILEY

摘要:

AbstractPhotoacoustic spectroscopy was used to monitor photo synthetic electron transfer in native and immobilized thylakoid membranes. The photoacoustic parameter ϕr′ (the percentage of absorbed energy that is stored in photo chemical intermediates) andi50(the half‐saturation modulated light intensity) were directly correlated to electron transfer rates. As previously shown, thylakoids immobilized in an albumin‐glutaraldehyde matrix were more resistant to aging. The inhibitory effects of the immobilization procedure and of aging at 4°C were detected as a decrease ini50values. In analogy with enzyme kinetic analysis, the effect could be characterized as a competitive type of inhibition. Photoacoustic measurements are performed in conditions similar to a working bioreactor cell with regards to the sample prep

ISSN:0006-3592    

DOI:10.1002/bit.260320110

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

年代:1988

数据来源: WILEY

摘要:

AbstractAggregates ofEscherichia coliconfined within hollowfiber reactors were either formed in place by culturing cells within the reactors, or were prepared by injecting a cell suspension that had been concentrated by centrifugation. The effective diffusive permeability of an uncharged nonreacting tracer, nitrous oxide, within the cell aggregates was calculated from measurements of the tracer flux through the aggregates. Estimates of the hydraulic permeability were also obtained for the aggregates that were grown in place. The effective diffusive permeability was found to decrease with increasing cell volume fraction to a value, for aggregates comprising 95% cells, of ca. 30% that obtained for cell‐free buffer solution. The dependence on the cell volume fraction was described adequately by the well‐known HashinShtrikman bounds for a two‐phase medium. The transport properties of aggregates cultivated in place were not significantly different from those of aggregates prepared by centrifugation. Furthermore, the effective diffusive permeabilities of the tracer in aggregates prepared from cells treated with detergent or disrupted by dehydration and grinding differed only slightly from the values obtained for aggregates formed from untreated cells. The results suggest that the method of formation of the cell aggregate and the details of the structure of the cells have little influence on the effective diffusive permeability. These findings should be applicable to the transport of other small uncharged solutes, such as oxygen, that can diffuse through cells. The hydraulic permeability estimates for the aggregates cultured in place were several orders of magnitude larger than the values predicted by a theory formulated with the assumption that the cells are impervious to flow and homogeneously distributed within the aggregates. Two possible reasons for this discrepancy are, first, that there is some flow through the cells themselves, and second, that the cells may form discrete clusters separated by relatively open re

ISSN:0006-3592    

DOI:10.1002/bit.260320111

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

年代:1988

数据来源: WILEY

摘要:

AbstractA theoretical analysis has been made of carbon conversion efficiency during heterotrophic microbial growth. The expectation was that the maximal growth yield occurs when all the substrate is assimilated and the net flow of carbon through dissimilation is zero. This, however, is not identical to a 100% carbon conversion, since assimilatory pathways lead to a net production of CO2. It can be shown that the amount of CO2produced by way of assimilatory processes is dependent upon the nature of the carbon source, but independent of its degree of reduction and varies between 12 and 29% of the substrate carbon. An analysis of published yield data reveals that nearly complete assimilation can occur during growth on substrates with a high energy content. This holds for substrates with a heat of combustion of ca. 550 kJ/mol C, or a degree of reduction higher than 5 (e.g. ethane, ethanol, and methanol). Complete assimilation can also be achieved on substrates with a lower energy content, provided that an auxiliary energy source is present that cannot be used as a carbon source. This is evident from the cell yields reported forCandida utilisgrown on glucose plus formate and forThiobacillus versutusgrown on acetate plus thiosulfate. This evaluation of the carbon conversion efficiency during assimilation also made it possible to compare the energy content of the auxiliary energy substrate added with the quantity of the carbon source it had replaced. It will be shown that utilization of the auxiliary energy source may lead to extreme changes in the efficiency of dissimilatory processes.

ISSN:0006-3592    

DOI:10.1002/bit.260320112

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

年代:1988

数据来源: WILEY