Enhanced Iturin A Production of Engineered Bacillus amyloliquefaciens by Knockout of Endogenous Plasmid and Rap Phosphatase Genes

Iturin A biosynthesis has garnered considerable interest, yet bottlenecks persist in its low productivity in wild strains and the ability to engineer Bacillus amyloliquefaciens producers. This study reveals that deleting the endogenous plasmid, plas1, from the wild-type B. amyloliquefaciens HM618 notably enhances iturin A synthesis, likely related to the effect of the Rap phosphatase gene within plas1. Furthermore, inactivating Rap phosphatase-related genes (rapC, rapF, and rapH) in the genome of the strain also improved the iturin A level and specific productivity while reducing cell growth. Strategic rap genes and plasmid elimination achieved a synergistic balance between cell growth and iturin A production. Engineered strain HM-DR13 exhibited an increase in iturin A level to 849.9 mg/L within 48 h, significantly shortening the production period. These insights underscore the critical roles of endogenous plasmids and Rap phosphatases in iturin A biosynthesis, presenting a novel engineering strategy to optimize iturin A production in B. amyloliquefaciens.