槽間移動における滞留令-活性分布について

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Taking the production of glucamylase by Aspergillus niger as an example, a theory of multistage continuous culture is developed for the product formation through nongrowth-associated metabolism. In the flucamylase production by an adenine-requiring mutant of Asp. niger, the maximum produciton rate is reached when the adenine-group substances are used up. Thus, the product formation lags remarkably behind the cell growth.In a multistage continuous system of three stages, mycelia right after the transformaiton from the growth (1st) stage to the production (2nd) stage, do not adapt themselves immediately to the new environment to become fully active, but there is always a time lag for it. Then the mycelia in the subsequent (3rd) stage, where the residual activity is utilized, show a tendency to maintain the activity which has been manifested in the preceding stage; the phenomenon is, so to speak, an activity tailing.Lag and tailing in the above sence can be expressed in terms of residence age-activity distribution function. The distribution funcitons are deduced from the results of shift-down experiments [Eq.(5), (6), (7) and (8)].The residence age-activity relationship in one stage ( e.g. 1st stage-mycelia in 2nd stage-filtrate) is quite different from another ( e. g.2nd stage-mycelia in 3rd stage-filtrate), although their funciton follows the rate law of monomoleculor autocatalysis without fail in each case. The above age-activity distribution function (ε_<γel>) expressed in relative scale is multiplied by dY_D/dθ to yield the age-production rate distribution funcition, ε_<γre'> (dY_D/dθ), which represents the activity of product furmation of mycelia of the residence age. Here, the Y_D represents the cumulative concentration-residence age distribution function, which is expressed by (1-e^<Dθ>) if the dilution rate is constant under complete mixing. The above products are integrated with a represented age from zero to θ to obtain the cumulative age-production rate distibution function [Eq.(2), (3)and (4)].which is useful in carrying out the computation of the production rate in the continuous culture on a theoretical basis. Mass balance equation is then derived Eq.(1).The continuous culture wich was started when the batch culture of mycelia grown in each vessel attained an appropriate age corresponding to the steady state of each stage. and the duration of each stage was compared with that deduced by calculation following the above equation. As shown in the figures, the calculated time course coincided fairly well with the practical ones, exvept the time of transient state in the 3rd stage.In the 3rd stage, the discrepancy arised from the fact that mycelia exsistent in the batch culture at the start became over-aged. The over-aged mycelia lost the activity in course of time. In the steady state, the over-aged mycelia were washed out, and the above mentioned discrepancy became insignificant.In the steady state treatment, the function I_k(=⎰^∞_0_<γel>(dYD_D/dθ)dθ) is impotant.The computation of I_k can be performed as shown in Eq.(28), (29), (34), (37) and (38).Approximation made in the cmputation is considered to produce few errors in practice, because, from the very nature of autocatalytic reaction, the value of α is much greater than the unity (Fig.1). If the function expressed by ε_<γel> obseves the monomolecular rate law, computation of I_k(I'_k) is very simple.We want to emphasize, finally, that the distribution funciton should be derived from the physiology and kinetics of shift down cultures using appropriate mycelia and suspending media.A single expression common to two or more stages cannot be obtained since the physiology and physicochemical conditions of a tage differ from another. so far as stages are limited to a small number.
社団法人日本生物工学会の論文
1964-05-15

槽間移動における滞留令-活性分布について

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