Stability and Phase-Plane Analyses of Continuous Yeast Culture on Ammonium Hydroxide : A Complicated Case

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Stabilities of the three steady states and transient behaviors were experimentally studied in a chemostat culture of Saccharomyces cerevisiae with ammonium hydroxide as growth-limiting substrate. Stabilities of the three steady were well predicted by the theory previously proposed by Yano and Koga(Biotechnol. Bioeng., 11,139,1969), but the steady states attained and transient behaviors were quite different from the theoretical predictions. It was found that(a)the specific growth rate responded after a time lag to changes in concentration of the growth-limiting substrate, (b)the yield coefficinet at steady state was a function of the dilution rate, and(c)the specific growth rate depended not only on the growth-limiting substrate concentration but also on the cell concentration.The response lag of the specific growth rate to a step change of ammonium hydroxide concentration involved a dead time, 0.2 hr, and two relaxation times, 1.4 hr and 8.8 hr.The yield coefficient Y and the specific growth rate μ were described as follows.Y_∞=Y_0-K_<μ∞> and μ=f(S)・g(X), g(X)=1/[1+(X/K_x)^m] where S and X are concentrations of the growth-limiting substrate and cells, respectively, and k, K_x, and m are constants. With these corrections, the experimental transient behavior was better analysed.
公益社団法人日本生物工学会の論文
1980-02-25