The fruity odor of Chinese liquor is largely derived from ester formation. Ethyl caproate, an ethyl ester eliciting apple-like flavor, is one of the most important esters in the strong aromatic Chinese liquor (or Luzhou-flavor liquor), which is the most popular and best-selling liquor in China. In the traditional fermentation process, ethyl caproate in strong aromatic liquor is mainly produced by aroma-producing yeast, bacteria, and mold with high esterification abilities in a mud pit at later fermentation stages at the expense of both fermentation time and grains rather than by the ethanol-fermenting yeast Saccharomyces cerevisiae. To increase the production of ethyl caproate by Chinese liquor yeast (S. cerevisiae AY15) and shorten the fermentation period, we constructed a recombinant strain EY15 by overexpressing EHT1 (encoding ethanol hexanoyl transferase), in which FAA1 (encoding acyl-CoA synthetases) was deleted. In liquid fermentation of corn hydrolysate and solid fermentation of sorghum, ethyl caproate production by EY15 was remarkably increased to 2.23 and 2.83 mg/L, respectively, which were 2.97- and 2.80-fold higher than those of the parental strain AY15. Furthermore, an increase in ethyl octanoate (52 and 43 %) and ethyl decanoate (61 and 40 %) production was observed. The differences in fermentation performance between EY15 and AY15 were negligible. This study resulted in the creation of a promising recombinant yeast strain and introduced a method that can be used for the clean production of strong aromatic Chinese liquor by ester-producing S. cerevisiae without the need for a mud pit.

• PMID: 24370880
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Journal Article | Research Support, Non-U.S. Gov't

Authors

Chen Y, Li F, Guo J, Liu G, Guo X, Xiao D

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