Glycerol Production by the Yeast Saccharomyces cerevisiae and its Relevance to Wine: A Review

  • K.T. Scanes Departrrient of Microbiology and Biochemistry and the UNESCO Industrial Biotechnology MIRCEN, University of the Orange Free State, PO Box 339, 9300 Bloemfontein, South Africa
  • S. Hohrnann Laboratorium voor Moleculaire Biologie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Hevelee, Belgium Department of General and Marine Microbiology, University of Goteborg, S-41390 Goteborg, Sweden
  • B.A. Prior Departrrient of Microbiology and Biochemistry and the UNESCO Industrial Biotechnology MIRCEN, University of the Orange Free State, PO Box 339, 9300 Bloemfontein, South Africa Department of Microbiology, University of Stellenbosch, Private Bag Xl, 7602 Matieland, South Africa

Abstract

Glycerol is a sugar alcohol produced as a by-product of the ethanol fermentation process by Saccharomyces cerevisiae. In wines, levels between 1 and 15 gll are frequently encountered and the higher levels are thought to contribute to the smoothness and viscosity of wine. Glycerol and ethanol levels are inversely related, which may add an additional favourable attribute to wine.  The metabolic pathways involved in glycerol synthesis, accumulation and utilisation by yeast are now better understood since a number of the genes involved in glycerol metabolism have been cloned, sequenced and their functions established. These fundamental studies now permit the glycerol levels produced by yeast to be raised by either the specific control of the culture conditions or by the manipulation of the genetic and molecular properties of the yeast. In some instances, the level of glycerol produced under laboratory conditions has been significantly raised. However, a number of undesirable by-products also accumulate during the fermentation and an improved understanding of the glycerol metabolic flux is required before wines with a consistently elevated glycerol concentration can be produced.
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