深部培養による酢酸醗酵の動力学的研究 : (第1報)酢酸菌の対酸素挙動

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Investigations were undertaken into the behavior toward oxygen of Acetobacter rancens cells grown in submerged cultures with a medium resembling one of those used in industrial acetic acid fermentation. The results are summarized as follows.(1) The time course of a batch culture showed a distinct feature of growth-associated product formation; a parallelism was observed among μ(specific growth rate), ρ(specific rate of acetic acid production) and σ_A(specific rate of ethanol utilization). The optimum pH for respiration lay between 4 and 5.(2) The instantaneous rate of respiration of existing cells could be expressed as a function of existing[O_2], which was shown to be in accord with the Michaelis-Menten type equation as analyzed by the method of half-value time plot according to Terui and Konno. The value of K_m for oxygen was estimated to be 10^<-7>〜10^<-6>M. The results together with the effect of[O_2]and azide on the oxygen utilization rate of cell-free extract, indicated that the respiration(or acid production)was limited by an oxygen-terminal entity, cytochrome oxidase, unless ethanol concentration was extremely lowered. Acetic and accumulated in the later phase of culture inhibited oxygen utilization; the type of inhibition seemed to be a mixed one composed of both noncompetitive and competitive inhibitions. So the apparent value of K_m for oxygen increased(affinity lowered)significantly by the action of acetate or acetic acid. Similar results concerning the effect of acetate were obtained with cell-free extracts, implying that acetic acid penetrated into the cytochrome site of living cells exerted such effects. The above results could not be explained simply by the effect of pH lowered by acetic acid.(3) The specific rate of adaptation of A. rancens cells to dissolved oxygen to form respiration rate-limiting enzyme(cytochrome oxidase)was investigated at various levels of[O_2]in oxystatted cultures. The kinetic analysis based on the hypothesis that the rate-[O_2]relationship obeys the Monod's kinetics, indicated that its fitness was good. The saturation constant(K'_8)was shown to be the same order of magnitude as those observed on some microbes by Terui and Konno. The peak values of μ(μ_p)observed in the time courses at various levels of[O_2]in oxystatted cultures could be expressed as a function of[O_2]maintained, which was also in accord with the type of Monod's equation : the value of saturation constant(K_8")was nearly equal to that of K_8' for oxyen adaptation.(4) A high level of[O_2]applied to the earlier phase of acid-producing cultures facilitated growth and acid production, but a sudden lowering of D. O. level form 1.1×10^<-4> to 2.8×10^<-5> in the later phase did not result in a significant lowering of production rate. The phenomenon was explained by taking into cosideration the inhibiting action of acetic acid which was accumulated as the culture was aged.
社団法人日本生物工学会の論文
1970-04-25

深部培養による酢酸醗酵の動力学的研究 : (第1報)酢酸菌の対酸素挙動

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