The Improvement of the Sensorial Quality of Wine


Project Number
IWBT 05-06

Project title
The improvement of the sensorial quality of wine

Project leader
Bauer, F F

Institution
University of Stellenbosch. Faculty of AgriSciences. Institute for Wine Biotechnology

Team members
Bauer, F F
Lilly, M
Potgieter, N
Van der Merwe, P
Malherbe, D F
Smit, A
Van Rensburg, P

Project description
This programme involves several projects that am to generate new wine yeast strains that would give winemakers additional choices to either enhance or reduce specific characteristics of the wines that they produce.

The projects aims are
(i) adjusting the levels of aroma compounds, in particular esters, that are produced by wine yeast during fermentation,
(ii) producing enzymes that will release additional volatile aroma compounds from the grapes and
(iii) reducing the amount of alcohol to levels which allow a better perception and release of aroma ad flavour compounds. (i) The synthesis of ethyl- and isoamyl acetate esters is ascribed to alcohol acetyltransferase activities, encoded by the ATF1 and ATF2 genes, and ethanol hexanoyl transferase, encoded by the EHT1 gene, is responsible for generating ethyl caproate. Esterases are responsible for the hydrolysis of these esters, and are encoded by the genes IAH1 and TIP1. Here we assess the effect of the increased levels of the above-mentioned enzymes on aroma compound concentrations in wine and brandy. The data show that ATF1 and ATF2 over expression increased the levels of ethyl-, isoamyl-, and 2-pheylethyl acetate and ethyl caproate in the wine, while IAH1 over expression, on the other hand, decreased the concentrations of ethyl-, isoamyl-, hexyl-, and 2-phenylethyl acetate drastically. Increased production of the other enzymes did not lead to significant changes in the aroma profiles of the wines. The data show that the targeted modification of specific enzymes in wine yeast strains can result in new strains with specifically modified aroma compound production capacity, without affecting the other enologically important characteristics of the parental wine yeast strains.

(ii) In an attempt to optimise the volatile aroma compound levels in wine, the Saccharomyces cerevisiae PAD1 gene (encoding phenyl acrylic acid decarboxilase), the Bacillus subtilis phenolic acid decarboxylase gene and the Lactobacillus plantarum para-coumaric acid decarboxylase gene were cloned. The bacterial genes were sub-cloned into yeast expression vectors and introduced into laboratory yeast strains to determine their activity and efficiency. The endogenous Saccharomyces cerevisiae PAD1 gene was both over-expressed and disrupted to determine the effect this has on the levels of volatile phenols in wine.

(iii) A further study in this programme attempts to reduce alcohol levels enzymatically. Together with the other concurrent strategies to overproduce glycerol at the expense of ethanol formation, the glucose oxidase producing yeast might offer a viable way to meet consumers’ demands for affordable low-alcohol wine. Micro vinification experiments have shown that a 1.8% drop in alcohol level is possible using laboratory yeast strains. This data need to be confirmed using a modified wine yeast starter culture. An unexpected result was that no drop in pH was observed.

Presentation(s)
Swiegers, J H, Vaz, F M, Pretorius, I S, Wanders, R J and Bauer, F F. 2002. Carnitine biosynthesis in Neurospora crassa: Cloning of a cDNA coding for a trimethyllysine hydroxylase and functional expression in Saccharomyces cerevisiae. Paper presented at the Cape Biotechnology Forum. September, Somerset West, South Africa.

Malherbe, D F, Van Rensburg, P, Du Toit, M, Cordero Otero, R R and Pretorius, I S. 2002. Expression of the Aspergillus niger glucose oxidase gene in Saccharomyces cerevisiae and its application in winemaking. Paper presented at the Cape Biotechnology Forum. Somerset West, South Africa..

Swiegers, J H, Pretorius, I S and Bauer, F F. 2003. Ras regulates the carnite shuttle bypass, the glyoxylate cycle, through suppression of cit2. Paper presented at the 21st International Conference on Yeast Genetics and Molecular Biology. 7-12 July 2003, Göteborg, Sweden.

Swiegers, J H, Vaz, F M, Pretorius, I S, Wanders, R J and Bauer, F F. 2003. Carnitine biosynthesis in Neurospora crassa: cloning of a cDNA coding for a trimethyllysine hydroxylase and functional expression in Saccharomyces cerevisiae. Paper presented at the Cape Biotechnology Forum, Somerset West, South Africa.

Lilly, M, Lambrechts, M G, Pretorius, I S and Bauer, F F. 2004. Engineering Saccharomyces cerevisiae for optimised aroma production. Paper presented at the 13th Conference of the South African Society for Microbiology. 2-5 April 2004, Stellenbosch, South Africa.

Malherbe, D F, Du Toit, M, Cordero Otero, R R, Pretorius, I S, and Van Rensburg, P. 2004. Low-alcohol yeasts that are able to bio-preserve wine. Paper presented at the 13th Conference of the South African Society for Microbiology. 2-5 April 2004, Stellenbosch, South Africa.

Malherbe, D F, Du Toit, M, Cordero Otero, R R, Pretorius, I S and Van Rensburg, P. 2004. Developing low-alcohol yeasts that are also able to bio-preserve wine. Paper presented at the 12th Australian Wine Industry Technical Conference, Melbourne, Australia.

Malherbe, D F, Du Toit, M, Cordero Otero, R R, Pretorius, I S and Van Rensburg, P. 2004. Low-alcohol yeasts that are able to bio-preserve wine. Paper presented at the 19th International Conference of the International Committee on Food Microbiology and Hygiene. 12-14 September 2004, Portoroza, Slovenia.

Van Rensburg, P, Stidwell, T, Lambrechts, M G, Cordero Otero, R R and Pretorius, I S. 2004. The application of ß-glucosidase producing recombinant wine yeast strains in wine production. Paper presented at the 18th Congress of the South African Genetics Society. 4-7 April 2004, Stellenbosch. South Africa.

Van Rensburg, P, Ubeda Iranzo, J F, Briones-Perez, A I, Potgieter, N, Arevalo Villena, M, Pretorius, I S and Cordero Otero, R R. 2004. Evaluation of ß-glucosidases from the grape native yeasts. Paper presented at the 13th Conference of the South African Society for Microbiology. 2-5 April, Stellenbosch, South Africa.

Kroppenstedt, S, Snoep, J L and Bauer, F F. 2005. The cycling of reserve carbohydrates in Saccharomyces cerevisiae, a mathematical model. Paper presented at the 22nd International Conference on Yeast Genetics and Molecular Biology. Bratislava, Slovakia.

Du Toit, M, Trollope, K M, Vivier, M A and Van Rensburg, P. 2005. Enhancing the wholesomeness of wine. Paper presented at the 18th International Congress of the South African Association for Food Science and Technology. 5-8 September, Stellenbosch, South Africa.

Malherbe, D F, Varela, C, Chambers, P J, van Rensburg, P and Pretorius, I S. 2005. Modulation of yeast enzymatic activities for the production of low alcohol wines. Paper presented at the 3rd International Congress of the South African Society for Enology and Viticulture. 28-30 July, Cape Town, South Africa.

Ranwedzi, N, Smit, P, Van Rensburg, P and Cordero Otero, R R. 2005. Optimization of ß-glucosidase activity in recombinant Saccharomyces cerevisiae. Paper presented at the 3rd International Congress of the South African Society for Enology and Viticulture. 28-30 July, Cape Town, South Africa.

Ranwedzi, N, Smit, A, Cordero Otero, R R and Van Rensburg, P. 2006. Optimizing ß-glucosidase enzyme production in wine yeast. Paper presented at the 14th Conference of the South African Society for Microbiology. 9-12 April, Pretoria, South Africa.

Malherbe, D F, Varela, C, Chambers, P J, Van Rensburg, P and Pretorius, I S. 2006. Modulation of yeast enzymatic activities for the production of low alcohol wines. Paper presented at the 14th Conference of the South African Society for Microbiology. 9-12 April 2006, Pretoria, South Africa.

Article
Lilly, M, Bauer, F F, Styger, G, Lambrechts, M G, Pretorius, I S. 2000. The effect of increased branched-chain amino acid transaminase activity in yeast on the production of higher alcohols and on the flavour profiles of wine and distillates, Applied and Environmental Microbiology, Mnth Feb v. 66 (2) (p. 744-753)

Swiegers, J H, Vaz, F M, Pretorius, I S, Wanders, R J A, Bauer, F F. 2002. Carnitine biosynthesis in Neurospora crassa: Identification of a cDNA coding for ß-N-trimethyllysine hydroxylase and its functional expression in Saccharomyces cerevisiae, FEMS Microbiology Letters, v. 210 (1) (p. 19-23)

Cordero Otero, R R, Ubeda Iranzo, J F, Briones-Perez, A I, Potgieter, N, Arevalo Villena, M, Pretorius, I S, Van Rensburg, P. 2003. Characterisation of the ß-glucosidase activity produced by enological strains of non-Saccharomyces yeasts, Journal of Food Science, v. 68 (8) (p. 2564-2569)

Malherbe, D F, Du Toit, M A, Cordero Otero, R R, Van Rensburg, P, Pretorius, I S. 2003. Expression of the Aspergillus niger glucose oxidase gene in Saccharomyces cerevisiae and its potential applications in wine production, Applied Microbiology and Biotechnology, v. 61 (5-6) (p. 502-511)

Smit, A, Otero, R R C, Lambrechts, M G, Pretorius, I S, Van Rensburg, P. 2003. Enhancing volatile phenol concentrations in wine by expressing various phenolic acid decarboxylase genes in Saccharomyces cerevisiae, Journal of Agricultural and Food Chemistry, v. 51 (17) (p. 4909-4915)

Malherbe, D F, Van Rensburg, P. 2004. Let the yeast do the work for you. Less the alcohol in the bottle, WineLand, Mnth Jun (p. 105-106)

Malherbe, D F, Van Rensburg, P. 2004. Let the yeast do the work and lessen the alcohol in the bottle, Wynboer Technical Yearbook, (p. 36-37)

Van Rensburg, P, Stidwell, T, Lambrechts, M G, Cordero Otero, R R, Pretorius, I S. 2005. Development and assessment of a recombinant Saccharomyces cerevisiae wine yeast producing two aroma enhancing ß-glucosidase encoded by the Saccharomycopsis fibuligeria BGL1 and BGL2 genes, Annals of Microbiology, v. 55 (1) (p. 33-42)

Lilly, M, Bauer, F F, Styger, G, Lambrechts, M G, Pretorius, I S. 2006. The effect of increased branched-chain amino acid transaminase activity in yeast on the production of higher alcohols and on the flavour profiles of wine and distillates, FEMS Yeast Research, v. 6 (5) (p. 726-743)

Lilly, M, Bauer, F F, Lambrechts, M G, Swiegers, J H, Pretorius, I S. 2006. The effect of increased yeast alcohol acetyltransferase and esterase activity on the flavour profiles of wine and distillates, Yeast, v. 23 (p. 641-659)

Paper
Malherbe, D F, Du Toit, M, Cordero Otero, R R, Pretorius, I S, Van Rensburg, P. 2005. Developing low alcohol yeasts that are also able to biopreserve wine, IN: Blair, R (ed). Proceedings of the 12th Australian Wine Industry Technical Conference. 24-29 July 2004, Melbourne, Australia. (p. 294-296) Australian Wine Research Institute, Adelaide, Australia.

Thesis
Potgieter, N. The evaluation of ß-glucosidase activity from wine isolated yeast. MSc. (p. 92) University of Stellenbosch, Stellenbosch.

FinalReport.pdf

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