Effects of Plant Oils and Minerals for the Inhibition of Lipase Activity of Staphylococcus aureus Isolated from Fermented Pork Meat

Staphylococcus aureus lipase is regarded as a virulence factor. The response of lipase activity to various factors can provide important insights concerning the prevention of S. aureus during meat fermentation. This study was conducted to evaluate the main effects of nutrients used in culture media, and their combined effects on the inhibition of lipase activity and cell growth of pathogenic S. aureus SK1593 isolated from fermented pork meat. A Plackett-Burman design was used to evaluate the main effects of variables, including olive oil, soybean oil, grapeseed oil, sesame oil, CuSO4, MgCl2, KNO3, CaCl2, and KCl. Significant negative effects on lipase activity were detected with soybean oil, grapeseed oil, KNO3, and CaCl2. Additionally, these nutrients were further selected as variables for the investigation of their combined effect on lipase activity, via response surface methodology. In order to confirm the regression model, a situation that only inhibits lipase activity was simulated. The predicted lipase activity and cell growth of the simulated situation were 14.0 U/mL and 9.6 log10 (CFU/mL), respectively, and the estimated value of those in the same medium showed 15.14 U/mL and 9.4 log10(CFU/mL) respectively. The lipase activity of the simulated medium was inhibited approximately 5-fold as compared to the basal medium, but no significant differences in cell counts were noted to exist between the basal and simulated media. These results suggest that soybean oil, grapeseed oil, KNO3, and CaCl2 can be used to inhibit the growth of pathogenic S. aureus during the process of meat fermentation.