Influence of Initial Colloid Content on Yeast Macromolecule Production and on the Metabolism of Wine Microorganisms

Abstract

The influence of initial colloid content on macromolecule production by Saccharomyces cerevisiae during alcoholic fermentation in synthetic media was investigated. The effect of yeast macromolecules on growth and malolactic fermentation of Leuconostoc oenos was also studied. Higher colloid concentrations had a diminishing effect on yeast extracellular macromolecule production during alcoholic fermentation. Two phases were observed in macromolecule release: (1) production of macromolecules by living cells in direct relationship with the initial concentration of colloids in the medium; and (2) production due primarily to dead cells in proportion to yeast autolysis. Media fermented with must colloids showed the lowest level of yeast macromolecules (4 mg/ L) and the highest level of fatty acids (13.2 µM), as well as delayed malolactic fermentation. The concentrations of fatty acids in the two media fermented without must colloids were different: 8.2 µM in the control and 10.4 µM in the medium initially containing cellulose. However, malolactic fermentation occurred rapidly in these two media with no significant difference. The yeast macromolecule releases were quite similar in these two media: 48 mg/L and 46 mg/L, respectively. These results suggest that yeast macromolecules present in the medium result in better bacterial growth.