Hydrolysis of esters by staphylococci

The objective of this work was to characterize the hydrolysis of esters by staphylococci in order to understand if they could contribute to the release of free fatty acids in sausage. Cell-free extracts and extracellular concentrates of staphylococci were examined for esterase activities against p-nitrophenyl esters and for lipolytic activities against triolein. Staphylococci showed intracellular and extracellular esterase activities with different esterase electrophoretic patterns. Cell-free extracts of S. xylosus, S. warneri and S. saprophyticus preferentially hydrolysed p-nitrophenyl butyrate whereas their extracellular concentrates were mainly active against p-nitrophenyl butyrate, p-nitrophenyl caproate and p-nitrophenyl caprylate. In addition their extracellular concentrates hydrolysed triolein. The two strains of S. carnosus differed as they did not show pronounced p-nitrophenyl substrate specificity and did not hydrolyse triolein. Staphylococci hydrolysed esters at a high rate between 15 and 25 °C; acidic conditions inhibited the hydrolysis. The hydrolysis was also reduced when the water activity was decreased by addition of polyethylene glycol or glycerol.