Breeding Aspergillus oryzae Strain with High Protease Activity by Ultraviolet Induced Mutation

Based on the assessment of protease (acid,neutral and alkaline protease) activity and amylase activity (α- amylase and β- amylase),one Aspergillus oryzae K61 was selected from five wild Aspergillus oryzae which are original from spontaneous fermented soybean paste.One Aspergillus oryzae Y29 was screened with ultraviolet radiation.The Aspergillus oryzae Y29 can produce higher protease activity than original Aspergillus oryzae K61,and its hereditary stability is higher.Compared with Aspergillus oryzae 3.042,the Aspergillus oryzae Y29 showed higher protease activity,however,the both strains did not have significant difference on the amylase activity,growing speed of the strain and number of spore.Both strains were applied to producing soybean paste.The soybean that was produced by Aspergillus oryzae Y29 has full-bodied soybean paste flavor,and the soluble nitrogen (0.77g/100ml) is higher than the Aspergillus oryzae 3.042.