米麹における代謝経過(第2報) : 米麹のpH経過とその要因について

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In the preceding report (J. Ferment. Technol., 34,575(1956), the time-course of metabolism of rice-koji, the culture of Aspergillus oryzae on steamed rice as medium, was studied, estimating mycelia weight by means of Taka-diastase digestion method in which mycelia could be separated as the digestion residue from a suspension of coarsely crushed koji.Specific activities (Q-values) of mycelia grown on steamed rice have been revealed since then. In the present investigation, the time-course of pH and some factors affecting the change of pH directly are investigated, and on the other hand, the distributions of mycelia and of pH in koji granules are followed by spraying dye solution over microtome-cut slices.The interior of a koji granule is highly heterogeneous in composition, therefore a pH-value measured with aqueous extract of koji may be regarded as an index representing an overall value.The aqueous extract is buffered so strongly that the change in quantity of distilled water for extraction in a range from 1 to 19 fold by weight of koji scarcely affects the value of pH.The time-course of pH thus followed shows a minimum in the vicinity of 4.5 after about 30 hours incubation, then turns upwards. Such a pH-minimum can also be presumed from the observation by B.C.G.-spray method applied to slices.Although organic acids increase steadily with time, the formation of ammonia becoming remarkable after about 30 hours seems to give rise to the inflection of pH-curve. As the organic acids presented in rice-koji, pyruvic, lactic, succinic, fumaric, malic, tartatric and α-ketoglutaric acids are demonstrated by paper-chromatography. Such a composition in organic acids seems to be common to the rice-koji prepared by cultivating Asp. oryzae strains.
公益社団法人日本生物工学会の論文
1957-08-15

米麹における代謝経過(第2報) : 米麹のpH経過とその要因について

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