Study on Compound Bran Qu of High-Yield Acidic Glucoamylase Rhizopus and Acetoin Bacillus
[Objective]This study is to improve the starch utilization rate and rich the flavor in vinegar fermentation.[Method]The acid glucoamylase-producing mold and acetoin-producing Bacillus in vin-egar koji were screened by transparent circle method and Voges Proskauer color reaction respectively.The ability of glucoamylase production and acetoin production were further determined.The preparation process of compound bran Qu was optimized by response surface method.[Result]A mold named SFM-1 that highly-yield acidic glucoamylase and a Bacillus strain SAU-1 generating acetoin were screened from vinegar Qu,and no antagonism was found between them.Strain SFM-1 and SAU-1 were identified as Rhizopus oryzae and Bacillus velezensis,respectively.The preparation procedure of bran Qu using both strains was optimized through response surface methodology.The optimal conditions were as follows:the inoculation ratio of strain SFM-1 and strain SAU-1 was 15:1 at the interval of 24 h,and the incubation temperature and period were 31℃and 72 h,respectively.Under these conditions,the biomass and sac-charifying power of bran koji reached the maximum,with demonstration as 8.94 lg spores/g of mold,9.81 lg CFU/g of Bacillus and 3 388.56 U/g of dry mash,respectively.[Conclusion]A strain of Rhizopus ory-zae and a strain of Bacillus velezensis with high yield of acid saccharifying enzyme were obtained,and the best preparation technology of compound bran Qu was optimized,which provided data reference for in-dustrial preparation and application of bran Qu.
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