THE COMBINED EFFECTS OF ENVIRONMENTAL-CONDITIONS RELATED TO MEAT FERMENTATION ON GROWTH AND LIPASE PRODUCTION BY THE STARTER CULTURE STAPHYLOCOCCUS-XYLOSUS

The ability of the meat starter culture Staphylococcus xylosus to grow and produce lipase at the environmental conditions relevant to fermen ted meat production was examined. The combined effect of temperature ( 10-30 degrees C), pH (5.1-6.0), salt concentration (1-9% w/v) and gluc ose (0 and 1% w/v) on the maximum specific growth rate of S. xylosus w as studied in a microbiological medium. Growth was estimated by optica l density measurements and growth curves were generated by fitting a m odified Gompertz equation to the growth data using non-linear regressi on analysis. Maximum specific growth rates were derived and submitted to response surface analysis to generate a quadratic model to predict the maximum specific growth rate of S. xylosus at any combination of t he variables. Results from the combined effects of temperature, pH, sa lt concentration and age of culture on the lipase production of S. xyl osus according to a similar statistical analysis showed that lipase pr oduction was influenced by pH, salt concentration and age of the cultu re, whereas it was not significantly affected by the temperature. Gene rally, in cases with vigorous growth, the level of lipase production w as high, and it was limited to a more narrow range of environmental co mbinations than growth. (C) 1996 Academic Press Limited