Effect of bacteriocin RSQ01 on milk microbiota during pasteurized milk preservation

Milk has high risk for microbial contamination. RSQ01, a bacteriocin, previously has shown potentiality for pasteurized milk preservation. This study analyzed the effects of RSQ01 on milk microbiota by comparison of bacterial number and composition in 3 pasteurized milk groups: controls without RSQ01, treatment group with the addition of 2× MIC (low concentration), and treatment group with the addition of 4× MIC RSQ01 (high concentration). Integrated 16S ribosomal DNA sequencing and metagenomics of these groups after 3 d of storage showed inhibition of RSQ01 on microbiota diversity. Pathogenic bacteria such as Salmonella showed a decrease in relative abundance after RSQ01 treatment, whereas probiotic bacteria such as Lactococcus showed an increase, indicating that RSQ01 contributed to milk preservation by maintaining a low abundance of pathogens and a relatively high abundance of probiotics. Further investigations revealed that milk preservation was primarily attributed to the ability of RSQ01 to decrease the relative abundance of genes related to metabolism of energy and nutrients (e.g., vitamins, lipids, and AA) of microbiota, with change of genetic, environmental, and cellular processes. Interestingly, RSQ01 generally reduced the relative abundance of virulence factors and quorum-sensing-related genes in microbiota, likely reducing virulence and resistance. The findings provided insights into microbiomics mechanisms regarding pasteurized milk preservation of bacteriocins.