Directed evolution of a β-1,3-1,4-glucanase fromBacillus subtilisMA139 for improving thermal stability and other characteristics

In order to improve some characteristics of a β‐1,3‐1,4‐glucanase from Bacillus subtilis MA139, directed evolution was conducted in this study. After error‐prone PCR, the β‐1,3‐1,4‐glucanase gene, glu‐opt , was cloned into the vector pBGP1 and transformed into Pichia pastoris X‐33 to construct a mutant library. Three variants named as 7‐32, 7‐87, and 7‐115 were screened from 8000 colonies. Amino‐acid sequence analysis showed that these mutants...