Screening of novel high-stability alkaline protease mutants

The invention belongs to the technical field of enzyme genetic engineering, and relates to screening of novel high-stability alkaline protease mutants. The high-stability mutants of alkaline proteasederived from bacillus clausii are screened by error-prone PCR. According to sequencing, The genes of the mutants respectively have GAT at site 747-749, GTT at site 859-861 and CTG at site 955-957; thecorresponding sequence mutation is that the site 165 mutates to Asp, the site 203 mutates to Val and the site 235 mutates to Leu respectively; and after fermentation for 48 hours, the enzyme activityvalues of the mutant fermentation broths are respectively 30U/mL, 41U/mL and 35U/mL, which are respectively 11%, 51% and 30% higher than enzyme activity of a fermentation broth with expression of a wild-type alkaline protease aprE recombinant strain. After the obtained fermentation broth is subjected to ultrafiltration and incubation at 40 DEG C for 48 hours, the enzyme activity retention rate ofthe alkaline protease mutan