Regulation of fermentative CO2 production by the food spoilage yeast Zygosaccharomyces bailii

Zygosaccharomyces bailii is a yeast that spoils foods by CO2 accumulation. Gas is mainly produced by alcoholic fermentation. To study the extent and r egulation of fermentative CO2 production in this yeast, we have evaluated t he relevance of the effect of oxygen (Pasteur effect) and sugar (Crabtree e ffect) concentrations. In controlled-batch cultures on glucose and fructose , the main difference observed was that catabolism on fructose was not affe cted by oxygen concentration while on glucose, ethanol production increased in the absence of oxygen. This behavior can be explained by a higher capac ity to transport fructose and the Crabtree effect. Manometric experiments w ith resting cells confirmed the limited respiratory capacity of Z. bailii a nd that, under these nongrowing conditions, cells retained the ability of p roducing an important amount of gas. The Pasteur effect was not important i n Z. bailii since the glucose kinetic parameters in continuous cultures Ir ere trot significantly affected by the oxygen concentration Continuous cult ure experiments also that the amount of gas produced depended on the oxygen concentration and the sugar consumption rate. For low sugar concentrations which imply low consumption rates, oxygen concentration was an important c ontrolling factor; however, at high sugar consumption rates, gas production became independent of oxygen concentration, or in other words, regulation was dominated by the Crabtree effect. (C) 1999 Elsevier Science Inc.