Fermentation properties of a wine yeast over-expressing the Saccharomyces cerevisiae glycerol 3-phosphate dehydrogenase gene (GPD2) |
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Authors: | MIGUEL de BARROS LOPES ATA -ur-REHMAN HOLGER GOCKOWIAK ANTHONY J. HEINRICH PETER LANGRIDGE PAUL A. HENSCHKE |
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Affiliation: | Australian Wine Research Institute, PO Box 197, Glen Osmond SA 5064, Australia;Department of Plant Science, Adelaide University (Waite Campus), PMB 1 Glen Osmond SA 5064, Australia;Cooperative Research Centre for Viticulture, PO Box 154 Glen Osmond SA 5064, Australia |
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Abstract: | Wine yeasts efficiently convert sugar into ethanol. The possibility of diverting some of the sugar into compounds other than ethanol by using molecular genetic methods was tested. Over-expression of the yeast glycerol 3-phosphate dehydrogenase gene ( GPD2 ) in a laboratory strain of Saccharomyces cerevisiae led to an approximate two-fold increase in the extracellular glycerol concentration. In the medium fermented with the modified strain, acetic acid concentration also increased approximately two-fold when respiration was blocked. A strain deleted for the GPD2 gene had the opposite phenotype, producing lower amounts of glycerol and acetic acid, with the latter compound only reduced during non-respiratory growth. A commercial wine yeast over-expressing GPD2 produced 16.5 g/L glycerol in a wine fermentation, compared to 7.9 g/L obtained with the parent strain. As seen for the laboratory strain, acetic acid concentrations were also increased when using the genetically modified wine yeast. A panel of wine judges confirmed the increase in volatile acidity of these wines. The altered glycerol biosynthetic pathway sequestered carbon from glycolysis and reduced the production of ethanol by 6 g/L. |
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Keywords: | wine fermentation yeast GPD2 glycerol 3-phosphate dehydrogenase glycerol biosynthesis |
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