Kinetics of yeast growth: inhibition-threshold substrate concentrations

Two Candida species and a Saccharomyces were grown on ethyl alcohol, acetic acid, ethyl acetate, and 1-butanol, and their growth rates at a series of concentrations of each substrate are reported. Substrate concentrations higher than a characteristic threshold substrate concentration S0 inhibited growth in accordance with a new relationship:[Formula: see text]where i is an inhibition constant and the other symbols have their usual meanings. Complete inhibition, that is, no growth, takes place when S = Si, the total inhibition concentration. Values of S0, Si, and i were calculated for the examples studied. Also discussed are the observed lag periods and also the lowered yields at high substrate concentrations.