The cloning and characterisation of yeast genes involved in the synthesis of long chain fatty esters for increased flavour production in brandy


Project Number
IWBT 02-04

Project title
The cloning and characterisation of yeast genes involved in the synthesis of long chain fatty esters for increased flavour production in brandy

Project leader
Bauer, F F

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

Team members
Lambrechts, M G
Gey van Pittius, M H
Lilly, M
Bayly, J C
Hignett, J S

Project description
– To clone genes involved in the synthesis and degradation of esters.
– To characterise the gene(s) and determine the regulation during fermentation.
– To modify the production of esters during rebate wine fermentations and to enhance the quality of brandy.

Esters, which impart fruity aromas to wine, are important contributors to the fermentation bouquet. These compounds are mostly concentrated in the heart fraction during distillation. Studies have shown that the total esters represent 10.5% and 16% of the total concentration of volatile compounds in Armagnac and Cognac, respectively. Esters are therefore an important contributor to brandy aroma.

In the project The cloning and transformation of brandy yeasts with the alcohol acetyltransferase-gene from brewing and whiskey yeasts we cloned the ATF1 gene, the only gene involved in ester production of which the DNA-sequence was known, and overexpressed it in several wine yeasts. The overexpression of the ATF1 gene resulted in an increase in ethyl acetate (134 mg/L to 439 mg/L) and isoamyl acetate (9.2 mg/L to 35.4 mg/L) in the rebate wine. These results indicate that the ester profile could be dramatically changed. For this reason, it was decided to systematically investigate the effect of the overexpression and disruption of acyl alcoholtransferases (ester synthesising enzymes) and esterases (ester catabolising enzymes) which had been identified by other groups. Five genes are currently under investigation: The acyl alcoholtransferases ATF1, ATF2 and EHT1, and the esterases TIP1 and IAH1.

Presentation(s)
Hignett, J S, Du Toit, M, Lambrechts, M G and Pretorius, I S. 2001. The disruption and overexpression of two esterase genes, TIP20 and IAH1, in industrial Saccharomyces cerevisiae. Paper presented at the 25th National Congress of the South African Society for Enology and Viticulture. 15-16 November, Somerset West, South Africa.

Bayly, J C, Du Toit, M, Lambrechts, M G and Pretorius, I S. 2001. The manipulation of the genes involved in the production of ethyl-and isoamyl acetate during the production of wine and brandy. Paper presented at the 25th National Congress of the South African Society for Enology and Viticulture. 15-16 November, Somerset West, South Africa.

Article
Van der Westhuizen, T J, Augustyn, O P H, Pretorius, I S. 1999. The value of long-chain fatty acid analysis, randomly amplified polymorphic DNA and electrophoretic karyotyping for the characterisation of wine yeast strains, South African Journal of Enology and Viticulture, v. 20 (1) (p. 3-10)

Lambrechts, M G, Pretorius, I S. 2000 Special issue. Yeast and its importance to wine aroma – a review, South African Journal of Enology and Viticulture, v. 21 (p. 97-129)

Thesis
Bayly, J C. 2002. Manipulating the levels of ethyl and isoamyl acetate during the production of wine and brandy. (MSc) University of Stellenbosch, Stellenbosch.

Hignett, J S. 2002. The deletion and overexpression of two esterase genes, IAH1 and TIP1 in Saccharomyces cerevisiae to determine their effects on the aroma and flavour of wine and brandy. University of Stellenbosch, Stellenbosch.

FinalReport.pdf

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