Identification of the Strain Which Highly Produces Protease and β-D-glucosidase Isolated from Shuidouchi Produced in Sichuan and Evaluating Its Ability of Producing Protease

Objective To select and identify the bacterium which highly produces protease and β-D-glucosidase from 72 strains of Shuidouchi from Sichuan, and to provide evidence for further research on its nutritional value and fermentation strain exploiting.

Methods Casein degradation test and pNPG chemical test were applied respectively to detect the capacity to produce protease and β-D-glucosidase of each strain. Characteristics of morphology, biochemistry, 16S rRNA and MALDI-TOF-MS were used to identify the fermentation strain, which genetic stability, curves of growth and enzyme producing were also obtained.

Results The strain with the highest enzyme activity of β-D-glucosidase (0.084 U/L) among the top 10 strains for producing protease was selected as the fermentation strain and was identified as Bacillus subtilis, which curves of growth and enzyme producing conformed as well. The result of genetic stability showed that capacity of enzyme producing was stable until the 10th generation.

Conclusion The fermentation strain which highly produced protease and β-D-glucosidase was selected from 72 strains of shuidouchi from Sichuan and was identified as Bacillus subtilis.