Biological Properties of S. warneri KYS-164 Isolated from Kefir Grains

Staphylococcus worderi KYS-164,\nisolated from homemade Tibetan kefir grains, produces bacteriocin-like\ninhibitory substances (BLIS), which are peptides with antimicrobial\nproperties, but have not been fully characterized. The research on\nBLIS will lay the foundation for mining new bacteriocins. In this\nstudy, the optimal culture conditions for the production of highly\nactive BLIS were found to be incubation at 30 °C and 120 rpm,\nand the most effective extraction method was ammonium sulfate precipitation\n(ASP) using ammonium sulfate at 80% saturation. The postantibiotic\neffect (PAE) of BLIS on Staphylococcus aureus CICC 10384 is significant, with a 4 × MIC BLIS concentration\nable to prolong the PAE to 2.39 h. BLIS has excellent biosafety, with\nno deleterious effects observed at 8 × MIC concentration. Gas\nchromatography-ion mobility spectrometry (GC-IMS) was used to analyze\nthe volatile compounds synthesized by Staphylococcus\nwarneri KYS-164 during its growth. Hydroxycitronellal,\nethyl pyruvate, and α-pinene were found to be unique substances\nproduced by this strain, which can provide fresh, refreshing floral\nand fruity aromas as well as strong pine and resinous aromas in the\nprocess of kefir grain fermentation of milk. Analysis of the S. warneri KYS-164 genome provided insights into\nthe major metabolic pathways in which genes expressed in this strain\nare involved. This study represents the first isolation of S. warneri KYS-164 from kefir grains prepared by\nTibetan families, and provides a comprehensive analysis of its physicochemical\nproperties. This research provides a solid foundation for better understanding\nand utilization of S. warneri KYS-164.