The ethanol fermentation kinetics as a function of the substrate type and concentration

Abstract

The ethanol fermentation kinetics depends on the strain specific properties, the fermentation medium composition and the culture conditions. The influence of the substrate concentration on the specific ethanol productivity has been a subject of research for many authors and this has resulted in different kinetic models describing adequately the obtained relations (1, 2, 3). The strain specific properties are of great importance for the product inhibition. The tolerance of the strain used towards high ethanol concentration determines the fermentation rate and the final concentration of the product (1, 4, 5). The relation between the specific ethanol productivity and the ethanol concentration is described adequately by different models concerning the physiology of the strain under study (6, 7, 8). Experiments with yeast strains Candida pseudotropicalis and Kluyveromyces fragilis have demonstrated a dependence of the ethanol inhibition on the substrate type for glucose and lactose (9, 10). There was no evidence for such comparative experiments with saccharose as the substrate. The purpose of the present article is using strain Kluyveromyces fragilis 129-1 to elucidate the dependence of the ethanol productivity on the substrate type and concentration for glucose, saccharose and lactose in order to optimize the fermentation process with respect to the ethanol production rate and final product concentration. © 1991 Taylor & Francis Group, LLC.