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The experiment was aimed to optimize enzyme production process of Aspergillus oryzae, improve the complex enzyme activity and dry matter digestibility. The enzyme production performance of As‐ pergillus oryzae strains was verified. After production of Aspergillus oryzae strains, viable bacterial enumeration, toxin detection, and in vitro digestion were performed. The activities of three hydrolases, cellulase, xylanase, and protease were utilized to optimize the inorganic salt, nitrogen source, water content, and carbon source in the fermentation matrix. The cultured Aspergillus oryzae was then subjected to in vi‐ tro digestion, and the total sugar content of the remaining residue was measured. Our results showed that Aspergillus oryzae strains could produce seven different types of enzymes: protease, cellulase, xylanase, lipase, amylase, phytase and pectinase. During the fermentation process, the contents of aflatoxins and corn gibberellic ketene aflatoxin were all lower than the limit values. The fermentation matrix with bran as substrate was cultured at 30 ℃ for 5 days with the addition of 4% seed kojae, 0.5% ammonium sulfate, 2% yeast extract, 2% bran and 55% water content. There were different enzyme activities measured: the cellulase activity was 15.30 U/g, the xylanase activity was 17.91 U/g, and the acid protease activity was 622.56 U/g. The activity of neutral protease was 1 822.56 U/g, and that of alkaline protease was 6 024.79 U/g. The addition of Aspergillus oryzae culture significantly increased the digestibility of corn straw (P<0.05), the digestibility increased by 59.46%, and the total sugar content in the residue of rice straw after digestion in vitro decreased by 9.12%. The findings demonstrated that the Aspergillus oryzae culture could lower production costs, increase feed utilization, and improve the digestibility of dry matter. [ABSTRACT FROM AUTHOR]

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