LuxR-Type Regulator RRP6 Positively Regulates the Biosynthesis of Plantaricin EF and Improves Its Production in Lactiplantibacillus plantarum 163

The two-component system HPK₆/RRP₆ related to the <i>pln</i> locus of plantaricin biosynthesis was screened out. The overexpression of LuxR-type regulator RRP₆ promoted the transcription of ABC transporter-related genes, thereby increasing plantaricin EF yield. Its yield in 163(<i>rrp₆</i>) reached 16.01 mg/L, which was 1.20-fold that of the original strain. The regulatory mechanism indicated that RRP₆ could bind to two sites of the <i>plnG1</i> promoter, promoting its transcription and translation, accelerating the secretion of plantaricin and auto-inducing peptide, and enhancing the extracellular plantaricin yield. Amino acids Q73, R144, T171, and Y175 play a crucial role in the binding of RRP₆. Furthermore, potential regulatory compensation within the <i>Lactiplantibacillus plantarum</i> 163 genome may compensate for the negative effects after the deletion of <i>rrp₆</i>. These results provide a novel strategy for increasing plantaricin EF yield, which facilitates its large-scale application as a natural and safe food preservative in agriculture and the food industry.