Efficient control of molds contamination through gene cluster regulation and enzyme rational design of iturin A

Molds are prevalent environmental contaminants, posing significant risks to both human and animal health. Iturin A, known for its potent antifungal activity, offers a potential solution for control of molds contamination. In this study, a novel strain Bacillus velezensis ZD122 was successfully screened for iturin A production and mold control, and the gene cluster ituDABC was identified to be responsible for iturin A synthesis by genomic analysis. Through inserting the promoter in front of ituA and ituD simultaneously, the production of iturin A of ZD-P5 were increased by 2.08-fold compared with the wild strain ZD122. Meanwhile, the malonyl-CoA transacylase ItuD was modified by rational design to obtain the beneficial mutant ItuD^R117A/C161A, resulting in a 74 % increase in iturin A yield compared to the control strain. Molecular dynamics simulations further elucidate the potential mechanisms underlying the enhancement of enzyme activity. Through combinatorial expression, the iturin A production of the optimized recombinant strain ZD-P5/pHY-ituD^R117A/C161A reached 1.32 g/L. The increased iturin A production significantly enhanced antifungal efficacy against various molds. In summary, this study provides a valuable microbial resource for the production of iturin A, offering efficient strategies for control of the mold contamination.