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Glycerol Production of Various Strains of Saccharomyces

1982; American Society for Enology and Viticulture; Volume: 33; Issue: 1 Linguagem: Inglês

1943-7749

F. Radler, Harald Schütz,

Fungal and yeast genetics research

The quantity of glycerol as principal by-product of the alcoholic fermentation depends to a large extent on the yeast strain. Different strains of Saccharomyces cerevisiae were found to form amounts of glycerol varying between 4.2 to 10.4 g/L. The formation of glycerol is regarded as a result of the competition between alcohol dehydrogenase and glycerol-3-phosphate dehydrogenase that compete for the reduced coenzyme NADH2. High and low glycerol forming yeast strains showed large differences in the activity of glycerol-3-phosphate dehydrogenase and only small variations in the activity of alcohol dehydrogenase. The total amount of glycerol formed was also influenced by amino acids. In thiamine deficient media a decrease in glycerol formation was observed. Experiments indicate a correlation between the formation of acetaldehyde and glycerol and the production of cell mass that may be of practical interest. Glycerol is by far the most important secondary product of fermentation. The glycerol content of wine may be of two different origins. A certain amount of glycerol is always formed by yeasts. Occasionally, glycerol is already present in the grape must, as has been observed by Mtihlberger and Grohmann (7). This glycerol is formed by Boyrytis cinerea, a fungus which frequently attacks grapes when they are produced in humid climates. The amount of glycerol formed by yeasts is generally assumed to be in the range of 1/10 or 1/15 of the alcohol formed (11). The formation of glycerol is not constant but depends on various factors. Early observations date back to the last century. Because of the sweet taste that is similar to glucose (11), a high content of glycerol may have a favorable effect on the taste of wines. Besides the yeast strain, such factors as oxygen, fermentation temperatures, and pH have been reported to influence the formation of glycerol. Within the normal range of conditions these factors are obviously not very important, particularly when the range of the pH is kept between 2.8 to 5.0. There is no doubt that the formation of glycerol does not only depend on the yeast strain, but also to a large extent on the composition of the fermentation medium. It is the purpose of this paper to show how environmental factors and characters of yeast strains influence the formation of glycerol during fermentation.