Response surface models to describe the effects of temperature, pH, and ethanol concentration on growth kinetics and fermentation end products of a Pectinatus sp.

Abstract

Growth curve data which had been fitted by use of the Gompertz and logistic functions have permitted the development of mathematical models to describe the growth of a Pectinatus sp. by several variables, namely, temperature, pH, and ethanol concentration. The activation energy of this microorganism was lower at 26 to 35°C than at 15 to 22°C. On the basis of the Arrhenius law, growth rate, maximum population density, and cell yield models have been developed by introducing the different activation energy (E(a)) values. According to the model, optimal conditions were 35°C, pH 6.5, and 0% (vol/vol) ethanol for the growth rate. For cell density and cell yield, optimal conditions were 32°C, pH 6.0, and 1% (vol/vol) ethanol. No growth was observed fur ethanol concentrations above 8% and pH values below 4.0. Other equations have also been made to describe the major end products fermented during fermentation by a Pectinatus sp. The synthesis of propionate and acetate is maximal at 28°C at pHs of 5.5 and 6.25, respectively. This model completes the model suggested by Membre and Tholozan (J. Appl. Bacteriol. 77:456-460, 1994), which includes only one variable, i.e., the glucose concentration.