The effect of increased yeast alcohol acetyltransferase and esterase activity on the flavour profiles of wine and distillates

Abstract

The fruity odours of wine are largely derived from the synthesis of esters and higher alcohols during yeast fermentation. The ATF1-and ATF2-encoded alcohol acetyltransferases of S. cerevisiae are responsible for the synthesis of ethyl acetate and isoamyl acetate esters, while the EHT1-encoded ethanol hexanoyl transferase is responsible for synthesizing ethyl caproate. However, esters such as these might be degraded by the IAH1-encoded esterase. The objectives of this study were: (a) to overexpress the genes encoding ester-synthesizing and ester-degrading enzymes in wine yeast; (b) to prepare Colombard table wines and base wines for distillation using these modified strains; and (c) to analyse and compare the ester concentrations and aroma profiles of these wines and distillates. The overexpression of ATF1 significantly increased the concentrations of ethyl acetate, isoamyl acetate, 2-phenylethyl acetate and ethyl caproate, while the overexpression of ATF2 affected the concentrations of ethyl acetate and isoamyl acetate to a lesser degree. The overexpression of IAH1 resulted in a significant decrease in ethyl acetate, isoamyl acetate, hexyl acetate and 2-phenylethyl acetate. The overexpression of EHT1 resulted in a marked increase in ethyl caproate, ethyl caprylate and ethyl caprate. The flavour profile of the wines and distillates prepared using the modified strains were also significantly altered as indicated by formal sensory analysis. This study offers prospects for the development of wine yeast starter strains with optimized ester-producing capability that could assist winemakers in their effort to consistently produce wine and distillates such as brandy to definable flavour specifications and styles.

Acetate ester production by Chinese yellow rice wine yeast overexpressing the alcohol acetyltransferase-encoding gene ATF2

“…The results showed that ATF2 overexpression significantly improved the acetate ester content of Chinese yellow rice wine. In the same manner, the expression level of ATF2 in the current study was expected to be an important limiting factor for ester synthesis in S. cerevisiae, confirming the results of Lilly et al (2006) and Verstrepen et al (2003b). These observations can inform the development of new production strategies and new yeast strains, allowing further optimization of rice wine flavor profiles in order to satisfy different sensory preferences of consumers, as well as contribute to a better understanding of the physiological role of acetate ester synthesis.…”

“…In 1962, Nordström demonstrated that esters are formed via an intracellular process catalyzed by alcohol acetyltransferase from acetyl coenzyme A and the corresponding alcohols. There are 3 types of AATase, namely, AATases, AATase I, and AATase II, which are encoded by ATF1, Lg-ATF1, and ATF2, respectively (Lilly et al, 2006).…”

“…The rate of acetate ester formation is mainly dependent on 2 factors: the concentration of the 2 substrates and the activity of the AATase (Yoshioka and Hashimoto, 1983). Lilly et al (2006) showed that the concentrations of ethyl acetate and isoamyl acetate produced by VIN13 overexpressing the ATF2 gene were 1.3-fold and 1.5-1.8-fold higher, respectively, than those seen for the control. Similarly, Verstrepen et al (2003b) demonstrated that ATF2 deletion resulted in an 18% decrease in isoamyl acetate formation, while ATF2 overexpression resulted in a 6-to 8-fold increase.…”

Screening of native yeast from Agave duranguensis fermentation for isoamyl acetate production

“…Studies on ester production by yeast have found that modifying parameters, such as components of the culture media and aeration conditions, have increased aroma production by three times (Etschmann. 2004;Lilly. 2006;Medeiros.…”

“…2010;Garde-Cerdán 2008). For example, the ester hydrolase activity in P. heedii CECT 11452 was 28 times higher than in P. anomala CECT 10590, while the alcohol acetyltransferase activity was 17 times higher in P. heedii CECT 11452 than in P. anomala CECT 10590 (Lilly 2006;Bisson 2010). Peddie (1990) reported that ester synthesis was very slow at the beginning of fermentation in liquid cultures of S. cerevisiae.…”