下水の微生物的処理にかんする基礎的研究 : 低濃度基質酸化速度と酸素適応

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Studies were conducted with oxidatively active bacteria, especially with a strain of Aerobacter aerogenes, isolated from active sludge. A kinetic model adopted in our studies is shown in Fig. 1,in which it is assumed that no rate-limiting barrier is existent between the oxygen-terminal and substrate-terminal entities. According to this model, the relation of respiration rate, V, to substrate concentration, (S), and to oxygen concentration, (A), can be expressed by the following equation : (V_m)/V=1+K_<ms>/((S))+K_<mA>/((A))+K_<ms>・K_<mA>/((S)(A)), where V_m is the maximum respiration rate, and K_<ms> and K_<mA&gr; are Michaelis constants referred to substrate and oxygen, respectively.The polarographic measurements of dissolved oxygen (DO) in cell suspensions sealed with liquid paraffin layer were carried out with rotating platinum electrode. Air was introduced into the electrode vessel repeatedly in order to follow the change of respiration rate until the substrate was used up. The change of substrate concentration was estimated indirectly on the bases of quatitative data obtained by the separate sets of experiments.Acetate was oxidized by A. aerogenes in accordance with the equation of complete combustion. Thus, the polarographic data could be analyzed as shown in Fig. 2. Glucose was oxidized somewhat incompletely, but the results of tracer experiments indicated that the difference from the theoretical value of complete combustion was not significant.Fitness of the above equation was established to the behaviors of A. aerogenes cells which had been grown aerobically and subjected to nitrogen-starvation treatment. But the K_<ms> relationship with acetate or glucose as substrate was shown to be dualistic : the values of 8×10^<-5> M and 2×10^<-5> M were obtained in a wide range of DO (Fig. 3). K<mA> was ca. 10^<-6> M with aerobically grown cell, but with anaerobically starved cells two values, 10^<-4> and 10^<-6>M, were obtained (Fig. 4 or 10). Such dualistic behaviors toward oxygen have already been reported from out laboratory with certain bacteria and mold. (Terui, Konno. 1960).The oxygen adaptation pretreatment for inducing respiratory enzymes was proved to be very effective in maintaining a considerably high rate of respiration after the cells were transferred to a condition of low DO. The pretreatment was more effective as the substrate concentration was higher (Fig. 8). For instance, the pretreatment of cells in a medium having a BOD value higher than 2000 at 95% air saturation for 2 hr or more could make the initial V_m value 2 or 3-fold. No remarkable decrease in the elevated activity was observed through anaerobic treatment for 18 hr (Fig. 9).
社団法人日本生物工学会の論文
1966-10-25

下水の微生物的処理にかんする基礎的研究 : 低濃度基質酸化速度と酸素適応

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