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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
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 9 (1967), S. 487-497 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The results of our survey of several mining operations have shown in every instance typical T. ferrooxidans bacteria to be present in the leaching solutions. The numbers of bacteria found are in general what, one would expect considering the chemical reactions occurring in these processes. A major difficulty is encountered when one considers the complex and unknown series of events which occur, as the bacteria-bearing, acidic, ferric-ion solution penetrates the massive ore dumps. Laboratory studies show microbial activity to be the major cause of rapid solubilization of copper sulfide ores. Field studies suggest that microbial activity cannot explain all observations in a typical leaching operation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 577-591 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The adsorption of albumin, γ-globulin, and fibrinogen was measured on three ex vivo polymeric shunt surfaces [polyvinyl chloride (PVC), Silastic, and segmented polyether urethane (Biomer)] exposed to flowing heparinized, canine blood in vivo. Small amounts of radiolabeled proteins were infused into anesthetized mongrel dogs and the deposition of radioactivity on the walls of femoral arteriovenous shunts was followed with time for two hours following initial blood-polymer contact.Previously, transient in vivo platelet and fibrin deposition onto PVC, Silastic, and Biomer was measured by a similar technique in the absence of anticoagulant. A time-dependent phase of thrombus deposition followed by thromboembolism was observed on the PVC and Silasticshunt surfaces but not on the Biomer surface. In the studies reported here on PVC and Silastic, fibrinogen adsorption was found to predominate initially, though it subsequently desorbed somewhat and was replaced by albumin and γ-globulin. On Biomer, the adsorption of all three proteins increased with time following initial blood contact and fibrinogen was less prominent initially. The PVC surface was found to become passivated with respect to further thrombogenesis after 60-min exposure to flowing blood, at which time a higher fraction of albumin was present on the surface compared to that at earlier blood contact times. These results indicate that rearrangement of adsorbed protein species occurs with time on polymer surfaces exposed to flowing blood in vivo. Early and predominant fibrinogen adsorption appears to be an important factor in the thrombogenic and embolic events observed on the PVC and Silastic shunt surfaces in vivo.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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