RESPONSE-SURFACE MODELS TO DESCRIBE THE EFFECTS OF TEMPERATURE, PH, AND ETHANOL CONCENTRATION ON GROWTH-KINETICS AND FERMENTATION END-PRODUCTS OF A PECTINATUS SP

Growth curve data which had been fitted by use of the Gompertz and log istic functions have permitted the development of mathematical models to describe the growth of a Pectinatus sp, by several variables, namel y, temperature, pH, and ethanol concentration, The activation energy o f this microorganism was lower at 26 to 35 degrees C than at 15 to 22 degrees C, On the basis of the Arrhenius law, growth rate, maximum pop ulation density, and cell yield models have been developed by introduc ing the different activation energy (E(a)) values, According to the mo del, optimal conditions were 35 degrees C, pH 6.5, and 0% (vol/vol) et hanol for the growth rate. For cell density and cell yield, optimal co nditions were 32 degrees C, pH 6.0, and 1% (vol/vol) ethanol, No growt h was observed for ethanol concentrations above 8% and pH values below 4.0, Other equations have also been made to describe the major end pr oducts fermented during fermentation by a Pectinatus sp, The synthesis of propionate and acetate is maximal at 28 degrees C at pHs of 5.5 an d 6.25, respectively. This model completes the model suggested by Memb re and Tholozan (J. Appl. Bacteriol. 77:456-460, 1994), which includes only one variable, i,e,, the glucose concentration.