Antimicrobial activity of Latilactobacillus sakei isolated from virgin coconut oil under pH and temperature stress

This study aimed to elucidate whether lactic acid bacteria (LAB) can be used as a bio-preservative and a natural antimicrobial agent to extend coconut oil shelf-life, even under stress conditions. Lactiplantibacillus plantarum and Latilactobacillus sakei were isolated from virgin coconut oil which was subjected to strong environmental stresses. L. sakei was sequenced by a universal primer of 16S rRNA for LAB and included as L. sakei subsp. sakei. The growth analysis was influenced by pH and the optimum rate was pH 9.0. Furthermore, there was no growth at pH 3.0. In addition, the antibacterial activities were estimated using the wells diffusion method and the results were evaluated based on the presence of a clear halo surrounding the wells. The antibacterial activities were optimum at pH 4.5-7.0 against Escherichia coli K12 JM109, Bacillus subtilis, and Staphylococcus aureus JCM 20624. The antimicrobial activity was evaluated under high temperatures of 60, 70, 80, 90, and 100°C. The results revealed that even at high temperatures, the cell-free supernatant of L. sakei still gave antimicrobial activity. Therefore, it was concluded that L. sakei has antimicrobial activities under environmental stresses and can be used as a bio-preservative for coconut oil.