This study aimed to enhance surfactin production in Bacillus subtilis by replacing the native promoter of the surfactin synthase operon (P srfA ) with the strong IPTG-inducible promoter Pgrac to address challenges in large-scale biosurfactant production. The engineered strain was developed through homologous recombination, creating an integration cassette fused via overlap extension PCR and transformed into B. subtilis RI4914....