Modificación genética de levaduras vínicas industriales para mejorar la producción de aroma secundario.

Abstract

Flavour is a wines most important distinguishing characteristic that stem from a complex, completely non-linear system of interactions among many hundreds of compounds. Wine flavour is classified according to the sources of the different compounds contributing to it. This include varietal flavour, flavour compounds originating from the grapes, fermentative flavour, produced by yeast during alcoholic fermentation and post-fermentative flavour, compounds that appear during the ageing process through enzymatic or physicochemical actions. It is well known that during fermentation processes, yeast cells produce a broad range of aroma-active substances, which greatly affect the complex flavour of wine. While these secondary metabolites are often formed only in trace amounts, their concentrations determine the flavour profile of these beverages. In the main secondary metabolites synthesised for S. cerevisiae are the volatile esters. Their are the product of an enzyme-catalyzed condensation reaction between acetyl-CoA and a higher alcohol. Several different enzymes are involved in formation of esters, which are encoded by genes ATF1 and ATF2. Furthermore, they can be hydrolyzed by esterase like IAH1 gene product. Therefore, a balance of these two enzyme activities controls accumulation of volatile esters. The aims of this study are to develop several molecular strategies to construct wine yeast strain that improve accumulation of acetate esters through genetic engineering. The strategies develops were: 1.- Construct disruptant strain that were lose ATF1, ATF2 and IAH1 gene, to resolve implication of gene product in volatile production. 2.-Ester overproduction by regulated over expression of ATF1 gene controlled TDH3 promoter gene and disruption IAH1 gene 3.- Alcohols over production by over expression of THI3 gene. In conclusion, this study has demonstrated that in the main strategy for improve fermentative flavour in wine is construct a genetically modified wine yeast which have heave and constitutive over expression of ATF1 gene