Overexpression of the PEP4 protease and BGL2 glucanase genes in wine yeast for enhanced autolysis
Van Rensburg, P
University of Stellenbosch. Faculty of AgriSciences. Institute for Wine Biotechnology
Lambrechts, M G
Muller, C A
Gey van Pittius, M H
Gundllapalli Moses, S B
– To enhance yeast autolysis by overexpression of the PEP4 protease and BGL2 glucanase genes.
– To increase tartrate and protein stability of wines by the enhanced release of mannoproteins.
– To enhance the malolactic fermentation.
Yeast autolysis is of significant importance in several wine products. Sparkling wine produced by the Methode Champenoise is dependent on yeast autolysis for the specific aroma profile and is also important for the size of bubble formation. Some white wines of the Chardonnay variety are fermented in wooden barrels with a 228 litre capacity and then allowed to remain on the yeast lees for several months during which yeast autolysis occurs. Yeast autolysis has also been shown to be important for the production of a full-bodied brandy. Recent research indicates that yeast autolysis might also contribute to tartaric acid and protein stability of wine. Therefore, yeast autolysis is important for the flavour of certain wine products. It is also of economical importance due to the slow speed with which autolysis occurs and the possible spoilage of wine.
The main aim of this project is to clone the BGL2 and PEP4 genes into appropriate expression vectors, in order to obtain high levels of the protease A and ß-1,3-endoglucanase. The focus will therefore be to produce a wine yeast to enhance yeast autolysis, to increase tartrate and protein stability and to enhance the malolactic fermentation.
Lambrechts, M G, Stanley, L C J, Lourens, K, Van Rensburg, P and Pretorius, I S. 1998. Improved autolysis of yeast cells during the sur lie production of wine. Paper presented at the 10th Congress of the South African Society for Microbiology. Durban, South Africa.
Lambrechts, M G, Stanley, L C J, Lourens, K, Van Rensburg, P and Pretorius, I S. 1998. Manipulation of autolysis in Saccharomyces cerevisiae. Paper presented at the 22nd National Congress of the South African Society for Enology and Viticulture. 12-13 November, Somerset West, South Africa.
Van Rensburg, P, Pretorius, I S. 2000. Enzymes in winemaking: Harnessing natural catalysts for efficient biotransformations – a review, South African Journal of Enology and Viticulture, v. 21 Special issue (p. 52-73)