Metabolic engineering of Bacillus subtilis for enhanced p-Coumaric acid production and antimicrobial applications.

p-Coumaric acid (p-CA) is widely utilized in the food, pharmaceutical and other industries, and has traditionally been derived from plant extraction or chemical synthesis. However, p-CA synthesized by the safe B. subtilis remains poorly explored. In this study, we first engineered a recombinant B. subtilis strain (PBK) capable of synthesizing p-Coumaric acid, achieving an initial yield of 3.81 mg L-1. A high-yielding strain PBnprE was then developed through promoter substitution, with a yield reaching 60.92 mg L-1, and the yield of PBnprE was further increased to 304.04 mg L-1 by optimizing fermentation conditions and substrates, showing an 80-fold increase over PBK. The optimized fermentation extract of PBnprE displayed increased antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, alongside enhanced DPPH and ABTS scavenging capabilities. Compared to PBK, the optimized extracts showed 4.81-fold higher in DPPH and 3.47-fold in ABTS scavenging, consistent with improved antioxidant properties driven by the increased presence of p-CA. This study first successfully constructed a high-yield p-CA producing engineered strain in B. subtilis, providing a valuable platform for synthesizing other secondary metabolites.