Screening of Molds in Traditional Soy Sauce Moromi and Analysis of Some Enzymatic Characteristics
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Abstract:
There are many types of microorganisms (most of which naturally occurring in the environment) participating in the fermentation of traditional soy sauce. The aim of this study was to isolate different molds from the traditional soy sauce moromi and examine their enzymatic activities. Forty-nine mold strains were isolated from moromi, among which 18 cultured mold strains with different morphologies were selected for molecular biological identification. The results revealed four genera, including Aspergillus, Penicillium, Cladosporium and Alternaria. Analysis of enzymes in these molds showed that the enzymatic characteristics were closely related to the mold species. Among which, the acid protease and β-glucosidase of Aspergillus niger (A. niger) were prominent, while neutral protease, glucoamylase and aminopeptidase of Aspergillus oryzae (A. oryzae), Aspergillus nomius and Alternaria alternate were prominent. According to enzymatic activity and strain characteristics, A. niger (AN1) and A. niger (AN2) were chosen to co-cultivate respectively with commercial A. oryzae to make mixed koji. It was found that the effect of the mixed koji with A. niger AN2 and A. oryzae was better. Compared with pure A. oryzae koji, the activities of neutral protease and acid protease in mixed koji increased by 42.84% and 22.27%, respectively, and the activities of glucoamylase and aminopeptidase also increased by 17.54% and 15.10%, respectively, indicating a high application potential. This study provides a theoretical basis for screening high-quality mold from moromi.
