Ester formation and specific activities of in vitro alcohol acetyltransferase and esterase by Saccharomyces cerevisiae during grape must fermentation
1993
Mauricio, J.C. | Moreno, J.J. | Valero, E.M. | Zea, L. | Medina, M. | Ortega, J.M.
We have investigated the relationship between the alcohol acetyltransferase (EC 2.3.1.84) and esterase activities and the extracellular and cellular concentration of acetate esters in two Saccharomyces cerevisiae varieties during fermentation of grape must. S. cerevisiae var. cerevisiae is a typical fermentative yeast, and S. cerevisiae var. capensis is a flor veil-forming yeast. After 24 h of fermentation, a strong synthesis of ethyl, isoamyl, and hexyl acetate esters was detected, which correlates with an increase of alcohol acetyltransferase (AAT) activity. This activity decayed afterward and underwent a slow increase throughout the stationary phase. After 10 days of fermentation, a diminution of these esters was observed, being coincidental with an increase in the esterase activity measured as the hydrolysis of isoamyl acetate. After 134 days, the AAT activity and the synthesis-related activity of the esterases were higher in the nonviable yeast cells of var. cerevisiae found in the sediment than in the viable yeast cells of var. capensis found in the veil. It is suggested that these activities could be used to get rid of toxic compounds from the medium. The esters so synthetized could then be utilized by the flor veil-forming yeasts during the aerobic metabolism established when the sugar content is exhausted.
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