Enhancing protease activity of Bacillus subtilis using UV-laser random mutagenesis and high-throughput screening

Increasing the peptide level of fermented soybean meal helps improve its nutritional value, so it is necessary to screen strains with high protease activity. In this study, UV-laser random mutagenesis was employed to treat Bacillus subtilis for the selection of high protease producers. A high-throughput screening (HTS) processed aided by a microtiter plate (MTP) was established to enhance the efficiency of screening. Five mutagenesis methods were employed to investigate the mutagenesis effect, among which the positive mutation rate was the highest in laser UV sequential mutation (LA-UV). Two mutants, UV-1–84 and LA-UV-1–11, were re-screened from 32 positive mutants, exhibiting excellent genetic stability and protease activity. Besides, fermented soybean meal test showed that peptide content of SBM fermented by mutants UV-1–84 and LA-UV-1–11 increased by 13.66% and 12.91% respectively, compared with the wild-type strain. The HTS process established in this study could be easily transferred to other similar high-yield strains.