Metabolic engineering of Bacillus subtilis 168 for the utilization of arabinose to synthesize the antifungal lipopeptide fengycin

Fengycin is a cyclic lipopeptide complex produced by Bacillus species. The focus of this study was to improve fengycin titer through promoter replacement and fatty acid pathway modification. Here, arabinose was used as a carbon source to study fengycin synthesis in B. subtilis 168. Firstly, the nitrogen source of the medium was investigated, and water-soluble soybean cake powder was identified as the optimal nitrogen source for fengycin synthesis, resulting in a titer of 121.20 mg/L. Secondly, the native promoter of the fengycin biosynthetic gene cluster was replaced with the phase-dependent promoter Pylb, which further increased fengycin titer to 137.05 mg/L. Thirdly, the synthesis of fengycin was further promoted through enhancing the supply of fatty acyl-CoA by deleting fadB as well as overexpressing yhfL, yngH and tesA. Fengycin titer of the resulting recombinant strain reached 258.41 mg/L. qRT-PCR revealed the underlying reason for the increase of fengycin synthesis. This study confirms the feasibility of using a phase-dependent promoter and fatty acid pathway modification to improve the titer of fengycin, providing a reference for the production of antifungal lipopeptide using arabinose.