Effect of osmotic potential of sugar on the biological activity of yeast.

摘要

The biological activities of osmophilic yeasts Saccharomyces kluyveri G29, S. cerevisiae S41 and Rhodotorula mucilaginosa [R. rubra] J38 at different concentrations (1-60%) of glucose and sucrose were studied during batch culture in shake flasks. Anincrease in osmotic potential (i.e. sugars concentration) increased the production of glycerol and ethanol (fermentation products), but markedly decreased the yeast biomass produced. Glucose tended to support better yeast growth than sucrose. S. kluyveri G29 produced more glycerol and ethanol from glucose than from sucrose, the ratio being 1.29 at 60% sugar and 1.15 at 10% sugar. S. cerevisiae S41 produced 2.96 times as much ethanol from 20% glucose as it did from 20% sucrose. In contrast, R. rubra J38biosynthesized more reserve materials (glycogen, trehalose and soluble sugars) as osmotic stress increased, and also produced more biomass, than the fermentative yeasts. Activity of alcohol dehydrogenase increased gradually as glucose concentration increased during S. kluyveri G29 culture, while beta-fructofuranosidase activity showed little change. Rates of oxygen consumption by yeast cells decreased gradually as glucose concentration increased. It is concluded that a high concentration of sugars suppresses oxygen uptake and consequently inhibits the respiratory enzymes.