Kick-starting evolution efficiency with an autonomous evolution mutation system.

Adaptive evolution is an effective strategy to obtain industrial strains with excellent performance, but this method is time-consuming and less efficient. To solve these problems, we constructed an autonomous evolution mutation system (AEMS) to promote the occurrence of mutations, based on the hierarchical dynamic control between the high-fidelity module and the mutagenic module. AEMS was applied in Bacillus subtilis to screen acetoin tolerance phenotypes and high-producing strains. The minimal inhibitory concentration of acetoin exhibited a large increase from 40 to 60 g/L, and acetoin production was increased by 42.8% compared to that of B. subtilis 168. Scaled-up production of acetoin with the directed evolution strain B. subtilis HS019 in a 30-L fermentor resulted in acetoin titer up to 82.5 g/L. These results indicated that AEMS could improve the efficiency of evolution and provide an effective method for obtaining tolerance phenotypes and high-producing strains.