Abstract

Polynomial models describing the individual and combined influences of solutes (sucrose and NaCl) and pH on the water activity (a_w) of nutrient broth systems (NBS) were established using Response Surface Methodology. For the sucrose-pH model, the linear, quadratic and interactive influences of sucrose concentration and pH significantly affected a_w; while only the linear and quadratic influences of NaCl and pH significantly affected a_w in NaCl-pH model. The resulting models were characterized with satisfactory goodness-of-fit and efficient predictive performance. The established models may be used in the estimation of NBS components to formulate growth media with desired physicochemical property combinations and may be applied when studying microbial behaviors such as in quantitative microbial ecology.

Key words: Microbial growth media, physicochemical properties, response surface methodology.