Adaptive Laboratory Evolution of Bacillus subtilis 168 for Efficient Production of Surfactin Using NH4Cl as a Nitrogen Source

Bacillus subtilis strain 168 is commonly used as a host to produce recombinant proteins and chassis for bio-based chemicals production. However, its preferred nitrogen source organic nitrogen, which greatly increases production costs. In this study, adaptive laboratory evolution (ALE) was improve B. growth using NH4Cl the sole source. The cell density (OD600) of mutant LJ-3 208.7% higher than that original strain. We also optimized metal ions in medium resulted further increase rate by 151.3%. Reintroduction sfp+ gene into led LJ-31 clone, restored LJ-3’s ability synthesize surfactin. fermentation system (C/N, aeration, pH) 5 L bioreactor. Dry weight 7.4 g/L surfactin concentration 4.1 were achieved mineral salt after 22 h batch with YP/S value 0.082 g/g YP/X 0.55 g/g. HPLC analysis identified isoforms produced synthetic C13-surfactin 13.3%, C14-surfactin 44.02%, C15-surfactin 32.79%. Hence, variant isolated ALE promising engineering efficient cost-effective variety metabolites.