ANTIMICROBIAL ACTIVITY OF METABOLITES PRODUCED BY NOVEL COAGULASE-NEGATIVE STAPHYLOCOCCI (CNS) ISOLATED FROM FERMENTED DAIRY PRODUCTS IN MALANG, INDONESIA

Yogurt and kefir are well-known fermented dairy products that provide many benefits to human health. Microorganisms contained in yogurt and kefir play an important role to produce bioactive metabolites, including eradicating pathogens. This study presents the antimicrobial activity of 12 strains isolated from kefir and yogurt samples obtained in Malang, Indonesia. Strain K3 from kefir shows the highest antimicrobial activity with the diameter of the inhibitory zone was 8.11±0.07 mm against Escherichia coli and 8.20±0.17 mm against Staphylococcus aureus. Phenotypic characterization through Gram-staining, endospore-forming, motility, catalase, oxidase, and carbohydrate fermentation test, and genotypic identification through the 16S rRNA gene sequencing and phylogenetic analysis was performed to identify the species of isolate. Based on the result, K3 was characterized as non-motile Gram-negative bacilli bacteria, tested negative in endospore formation, catalase, and oxidase. According to the nucleotide sequence of 16S rRNA gene, the isolate was classified as Staphylococcus saprophyticus strain UTI-045 with 100% of similarity. Furthermore, the GC-MS analysis of the strain’s cell-free supernatant (CFS) reveals 3,6-Dioxa-2, 7-disilaoctane, 2,2,4,7,7-pentamethyl- (Rt=9.449 min); and Propanoic acid, 2-[(trimethylsilyl)oxy]-, trimethylsilyl ester (Rt=11.328 min) as the active metabolites.