清酒醸造における酵素バランスについて : (第3報) もろみ中Amylaseの動力学的検討。α-AmylaseとGlucamylase混合酵素液の蒸米に対する作用

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With a view that the rate of glucose formation in sake-mash is of great importance in dealing with the control of mash fermentation process, we investigated the kinetics of glucamylase action in the mash. In a previous report, two kinetic equations were derived separately for α-amylase and glucamylase reactions with steamed rice as the substrate. But, in practice, the two enzymes act on the substrate in conjunction. According to the results of experiments on the two-enzyme system, the initial, rapidly digesting action of α-amylase on steamed rice was followed by the saccharifying action of glucamylase on three kinds of substrates, namely maltose, dextrin and starch; the last substrate was found almost exclusively in the residual steamed-rice granules. Theoretically, the overall rate (v_T, mg glucose/ml・hr) of glucamylase action can be expressed by v_T=v_M+v_D+v_R, in which suffixes, M, D and R, denote the three substrates, i.e. maltose, dextrin and starch, respectively. On the other hand, it was preliminarily established that the rate of glucose formation is almost independent of whether or not the "ineffective adsorption" (cf. previous report) on α-amylase takes place. Equations of v_M, v_D and v_R as functions of substrate and initial enzyme concentrations were derived (Eq. 5〜7 in the text), and the fitness of these equations to some model reaction systems was confirmed. Using Michaelis constants, and rate constants in the rate estimation, it was shown that the direct action of glucamylase upon steamed rice granules was very weak as compared with its action on the α-amylase digests. The reaction rate of glucamylase was presumed to be maximum throughout the main phase of mash fermentation because (1) the overall substrate concentration was high (cf. Fig 6) and (2) the initial glucamylase concentration did not exceed 40 units/ml. The following relationships were calculated for the reaction rates, at 11℃ and of pH 4.4. v_T=0.0467 [E_0] for Aspergillus niger glucamylase; v_T=0.0400 [E_0] for Aspergillus oryzae glucamylase. Here, E_0 is the initial enzyme concentration (units/ml of the liquid phase of mash). On the other hand, the practical time courses of digestion of steamed rice (Fig. 1〜4 were in accord with the following relationships (cf. Fig. 9) : v_T=0.0327 [E_0] for A. niger glucamylase; v_T=0.0280 [E_0] for A. oryzae glucamylase. The differences between the calculated and practical values proved to be due to the effect of a lees-like substance formed in the course of the digestion. From the results of the digestion experiments with added lees, it was inferred that about 30% of the glucamylase activity might be lost by the effect of lees in the mash. The above relationships are concerned with the potential rates of glucose formation, since in practice, glucose formed is fermented and such a process may have some effect upon the rate of digestion.
社団法人日本生物工学会の論文
1971-11-25

清酒醸造における酵素バランスについて : (第3報) もろみ中Amylaseの動力学的検討。α-AmylaseとGlucamylase混合酵素液の蒸米に対する作用

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