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  • 1
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This work concerns mathematical modeling of the rate of microbial growth on inhibitory levels of nutrients as affected by pH, concentration of the nutrients, temperature, cultivation method, and method of data analysis. Candida utilis (ATCC 9226) was grown with sodium acetate as growth-limiting carbon and energy source in mineral salts medium in shake flask and continuous cultures to study inhibition by excess acetate. Differential shake flask cultures were grown at low yeast concentrations at temperatures (T) of 25 and 30°C, pH's between 5.5 and 7.0, and acetate concentrations (S) between 0.25 and 3.0% (w/v). Growth data were exponential with correlation coefficients greater than 0.995 in 49 of 56 experiments; the lowest correlation coefficient was 0.986. Specific growth rates (μ) determined by graphical methods showed only fair correlation with those determined by regression analysis. Both sets of specific growth rate data were grouped at constant T and pH and fitted to the three parameter equation, \documentclass{article}\pagestyle{empty}\begin{document}$$\mu = \mu _m /(K_s + S + S + S^2 / K_i )$$\end{document}The improvement in use of the fitted equation instead of the mean value was significant with greater than 70% confidence in all (14 groups) and 90% confidence in only half of the data groups; the correlation does not improve with the increasing acetate inhibition at lower pH. Both defects in the model and insufficient data at each pH are responsible. A modified six parameters with hydrogen ion concentration(H+) as follows: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {\mu _m = \mu _m /(1 + K_2 /{\rm H}^ + + {\rm H}^ + /K_1 )} \\ {K_i = K_I (1 + {{K_3 } \mathord{\left/ {\vphantom {{K_3 } {{\rm H}^ + }}} \right. \kern-\nulldelimiterspace} {{\rm H}^ + }})} \\ {K_s = {\rm Contant}} \\ \end{array} $$\end{document} Specific growth rates calculated with the six parameter equation matched observed values in all groups of isothermal data better than the means with greater than 99% confidence. The six parameter model adequately represents effects of acetate and hydrogen ion concentrations under constant or slowly changing environmental conditions and balanced growth; although better models probably exist. Thus steady-stste and transient continuous culture experiments agreed with many published growth yields, but specific growth rates could only be predicted qualitatively from the model fit to the shake flask data. The data and present models could be incorporated into published models for transient growth at low nutrient concentrations to correlate and perhaps predict microbial growth kinetics over a much wider range of growth conditions than now possible.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pseudomonas fluorescens (ATCC 11150) was grown in batch and continuous culture in minimal media with sodium maleate as growth-limiting sole organic carbon source. Growth was followed by turbidity and dry weight measurements. Gross composition of washed cells (relative amounts of protein, lipid, RNA, and DNA) and the distribution of amino acids in protein hydrolyses of the cells were determined for cells grown in continuous culture at various dilution rates. Extracellular concentrations of the original carbon source and a number of metabolites were monitored by a total carbon analysis, ion exchange chromatography, and ultraviolet-visible scans of cell-free supernatants and chromatographic fractions, thereof.Substrate inhibition by maleate was a major factor in the growth kinetics of both batch and continuous cultures. Excessive maleate concentration caused instability in continuous cultures. By appropriate operation, much higher specific growth rates (0.305/hr) could ultimately be achieved in continuous culture compared to batch culture (0.174/hr). Adaptation was responsible for only part of the differences between batch and continuous cultures; the differing distribution of metabolites were also major factors.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 99-102 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 16 (1997), S. 147-151 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Advanced methods for the design of emergency relief systems were developed under the auspices of the AIChE Design Institute for Emergency Relief Systems (DIERS). Rapid progress has continued, but most testing has been done at laboratory or small pilot plant scale. Full scale tests of design methods for emergency relief systems are much needed, but would be prohibitively expensive.Proposed here is a practical alternative: Use existing production data from operating plants to test design methods for emergency relief systems. Fortunately, although most emergency pressure relief events represent plant upsets and lost production, the relief system prevents a catastrophe in most process upsets. However, the qualitatively successful operation of an emergency relief system in a given upset does not represent proof of the design method employed. More importantly, it does not guarantee that the existing relief system will perform successfully in every credible upset that the process might experience in the future.Advocated here is an industry-wide program to use data from selected process upsets to systematically evaluate the effectiveness of current emergency relief system design methods to quantitatively predict the performance of existing emergency relief systems. Products of this effort would include confirmation of a significant number of existing design methods, identification of deficiencies in current methods, and a published compendium of documented and evaluated case histories of full-scale relief system performance. In addition to its instructive value to workers in emergency relief, the compendium could be used to test new design methods.This proposal is offered to the AIChE DIERS Users' Group. The DIERS Users' Group, which is comprised of over one hundred member companies, has representatives qualified to define, organize, sponsor, and execute a multi-company research program of this type. (NOTE: At the semiannual meeting of the AIChE DIERS Users' Group in Calgary, Alberta, Canada on September 9, 1996, this proposal was presented to and adopted by the DIERS Users' Group and assigned to the Case Histories Committee.)
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Inhibitory substrate levels are common in industrial fermentations and in biological waste-water treatment of many industrial wastes. Continuous microbial cultures are unstable to certain disturbances, such as shock loading by inhibitory substrates. Two feedback proportional control strategies are analyzed and compared for a simple model culture assumed represent able by the culture concentrations of biomass and a single rate-limiting and growth-limiting nutrient (substrate). One control strategy, the well known turbidostat, consists of adjusting culture holding time (e.g., by flow rate adjustment) in response to deviations in turbidity or some other measure of culture biomass concentration. The other control strategy is to adjust holding time in response to deviations in limiting nutrient concentrations in the culture. This second control strategy, termed the nutristat, can be superior to the turbidostat in many applications. The sign and magnitude of the dimensionless group {(X/YD)[dμ/dS]s}, is shown to be an important determinant, in the behavior of the open loop and the two closed loop processes. This characteristic group is positive when the specific growth rate is increased by increases in the nutrient concentration, zero when the growth rate is unaffected by the nutrient concentration, and negative in the presence of nutrient or substrate inhibition.The effects of process modifications and of modeling assumptions on the control of the process are discussed and more sophisticated control schemes are also proposed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 12 (1970), S. 679-712 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High substrate concentrations inhibit growth and may distort the metabolism of microorganisms. Mechanisms causing substrate inhibition are discussed and used to derive several mathematical models representative of the entire concentration range, including stimulation of growth by low substrate concentrations. These kinetic models are tested with a variety of batch culture measurements of specific growth rate and respiration rate at widely-ranging substrate concentrations. Using one of the kinetic models, equations are developed for batch, continuous, and exponential-feed reactors. Comparison of results obtained in continuous culture with results from exponential-feed culture systems is shown to offer a novel experimental method for evaluating the effect of the cell age distribution on the properties and metabolic activity of a culture.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 10 (1968), S. 205-232 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A generalized logistic equation is proposed for the mathematical representation of batch culture kinetic data. Properties of the equation are discussed. A computer program is used to fit the generalized equation to both artificial and actual batch culture data. The equation is shown to be capable of fitting data exhibiting lag, exponential, deceleration, stationary, and death phases, as well as diauxic growth. The fitted equation is useful for differentiation, interpolation, and other manipulations of the data, and it is a convenient means of data storage.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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