Abstract:

To obtain the strains with high-production glucoamylase and strengthen the production of Daqu, with Zhang Gong Liquor Daqu as test material, a strain WD11 with high-production glucoamylase was screened initially with the transparent circle method and re-screened through measuring enzyme activity method. The initial enzyme activity was 101 U/mL, and the strain was preliminarily determined and belonged to bacillus genus by 16S rDNA sequence homology analysis. Based on the above, the strain was also studied by the physiological and biochemical characteristics analysis. The results showed that methyl red test, V.P test, nitrate and ornithine reaction presented positive, lysine showed negative. Therefore, WD11 strain was identified as Bacillus amyloliquefaciens. After that, the conditions of enzyme production were optimized by orthogonal experiment. The results showed that, on the solid fermentation medium, with the sorghum flour as the optimal carbon sources (mass fraction 2%), peptone as the optimal nitrogen source (mass fraction 4%), and the inoculated quantity of 6%, the saccharifying enzyme activity was up to 160 U/mL, which was1.6 times that of the initial enzyme activity. The strain is expected to increase the liquor yield.

Key words: Luzhou-flavor Daqu, glucoamylase, molecular identification, single factor test, orthogonal optimization