Effect of Increased Yeast Alcohol Acetyltransferase Activity on Flavor Profiles of Wine and Distillates

Abstract

The distinctive flavor of wine, brandy, and other grape-derived alcoholic beverages is affected by many compounds, including esters produced during alcoholic fermentation. The characteristic fruity odors of the fermentation bouquet are primarily due to a mixture of hexyl acetate, ethyl caproate (apple-like aroma), iso-amyl acetate (banana-like aroma), ethyl caprylate (apple-like aroma), and 2-phenylethyl acetate (fruity, flowery flavor with a honey note). The objective of this study was to investigate the feasibility of improving the aroma of wine and distillates by overexpressing one of the endogenous yeast genes that controls acetate ester production during fermentation. The synthesis of acetate esters by the wine yeast Saccharomyces cerevisiae during fermentation is ascribed to at least three acetyltransferase activities, namely, alcohol acetyltransferase (AAT), ethanol acetyltransferase, and iso-amyl AAT. To investigate the effect of increased AAT activity on the sensory quality of Chenin blanc wines and distillates from Colombar base wines, we have overexpressed the alcohol acetyltransferase gene (ATF1) of S. cerevisiae. The ATF1 gene, located on chromosome XV, was cloned from a widely used commercial wine yeast strain of S. cerevisiae, VIN13, and placed under the control of the constitutive yeast phosphoglycerate kinase gene (PGK1) promoter and terminator. Chromoblot analysis confirmed the integration of the modified copy of ATF1 into the genome of three commercial wine yeast strains (VIN7, VIN13, and WE228). Northern blot analysis indicated constitutive expression of ATF1 at high levels in these yeast transformants. The levels of ethyl acetate, iso-amyl acetate, and 2-phenylethyl acetate increased 3-to 10-fold, 3.8-to 12-fold, and 2-to 10-fold, respectively, depending on the fermentation temperature, cultivar, and yeast strain used. The concentrations of ethyl caprate, ethyl caprylate, and hexyl acetate only showed minor changes, whereas the acetic acid concentration decreased by more than half. These changes in the wine and distillate composition had a pronounced effect on the solvent or chemical aroma (associated with ethyl acetate and iso-amyl acetate) and the herbaceous and heads-associated aromas of the final distillate and the solvent or chemical and fruity or flowery characters of the Chenin blanc wines. This study establishes the concept that the overexpression of acetyltransferase genes such as ATF1 could profoundly affect the flavor profiles of wines and distillates deficient in aroma, thereby paving the way for the production of products maintaining a fruitier character for longer periods after bottling.

Evolution of aromatic compounds during the second fermentation and aging of Brazilian sparkling wine

“…The sparkling wine flavor are the result of a complex interactions between three factors: grape varietal aromas, yeast derived fermentative compounds, and enological methods adopted during the first and second fermentation, and aging processes [3,7,8].…”

Decreasing the Level of Ethyl Acetate in Ethanolic Fermentation Broths ofEscherichia coliKO11 by Expression ofPseudomonas putida estZEsterase

“…In a typical fermentation containing 10% xylose, ethanologenic E. coli strain KO11 produced about 4.8% ethanol and 192 mg of ethyl acetate liter Ϫ1 (Table 2). This level of ethyl acetate is 4-to 10-fold higher than the level typically observed with yeasts (5,6,11,26,30,38,41). In yeasts and presumably other organisms, the level of ethyl acetate is mod- ) were tested by using the methyl red assay and were found to lack the ability to hydrolyze ethyl acetate.…”

“…Yeast-based ethanol fermentations result in minor products which copurify with ethanol (5,6,11,26,30,38,41). While many of these products are desirable as organoleptic agents and congeners in beverage alcohols, removal of the contaminating compounds to produce pure ethanol requires additional investment.…”

“…Potentially, this reaction could be catalyzed by many different acetyltransferases as ethanol accumulates. In yeasts, ethyl acetate production has been ascribed to three acetyltransferases (26), although more than 10 additional candidates are also present on the annotated genome (http://genome-www.stanford.edu/Saccharomyces/). The E. coli genome contains at least 13 genes encoding acetyltransferase-or esterase-like proteins with various substrate specificities (4).…”

Characterisation of banana wine fermented with recombinant wine yeast strains

“…These advances in DNA technology have made it possible to clone genes with traits of interest to the winemaker and to manipulate organisms' cells to overproduce the desired protein. During the last 18 years, several attempts to construct genetically engineered yeast strains have been published, and very interesting improvements in the wine-making process or the quality of the wine obtained have been reported, including improved primary and secondary flavors, malic acid decarboxylation by yeast, increased resveratrol, lactic acid, or glycerol contents, and improved survival properties (Barros et al, 2000;Dequin et al, 1999;Ganga et al, 1999;Gil and Valles, 2001;Gonzales-Candelas et al, 2000;Lilly et al, 2000;Perez-Torrado et al, 2002;Remize et al, 1999;Smit et al, 2003;Vilanova et al, 2000;Volschenk et al, 2001). Many enzymes have been expressed in manipulated micro-organisms at levels of 10 to 100 times higher than in their natural host cells (Kresse, 1995;.…”