Modulation of glycerol and ethanol yields during alcoholic fermentation in Saccharomyces cerevisiae strains overexpressed or disrupted for GPD1 encoding glycerol 3-phosphate dehydrogenase.
The possibility of the diversion of carbon flux from ethanol towards glycerol in Saccharomyces cerevisiae during alcoholic fermentation was investigated. Variations in the glycerol 3-phosphate dehydrogenase (GPDH) level and similar trends for alcohol dehydrogenase (ADH), pyruvate decarboxylase and glycerol-3-phosphatase were found when low and high glycerol-forming wine yeast strains were compared. GPDH is thus a limiting enzyme for glycerol production. Wine yeast strains with modulated GPD1 (encoding one of the two GPDH isoenzymes) expression were constructed and characterized during fermentation on glucose-rich medium. Engineered strains fermented glucose with a strongly modified [glycerol] : [ethanol] ratio. gpd1delta mutants exhibited a 50% decrease in glycerol production and increased ethanol yield. Overexpression of GPD1 on synthetic must (200 g/l glucose) resulted in a substantial increase in glycerol production ( x 4) at the expense of ethanol. Acetaldehyde accumulated through the competitive regeneration of NADH via GPDH. Accumulation of by-products such as pyruvate, acetate, acetoin, 2,3 butane-diol and succinate was observed, with a marked increase in acetoin production.
Michnick
S
S
Laboratoire de Microbiologie et Technologie des Fermentations, INRA-IPV, Montpellier, France.
Roustan
J L
JL
Remize
F
F
Barre
P
P
Dequin
S
S
D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D015870:Gene Expression; D005800:Genes, Fungal; D005990:Glycerol / Q000378:metabolism*; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
D017931:DNA Primers; D007527:Isoenzymes; D000431:Ethanol; D005993:Glycerolphosphate Dehydrogenase; D005990:Glycerol