title: Enhanced ethyl caproate production of Chinese liquor yeast by overexpressing EHT1 with deleted FAA1.
abstract: 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.
authors.affiliation: Key Laboratory of Industrial Fermentation Microbiology of Ministry of Education, Tianjin Industrial Microbiology Key Lab, College of Biotechnology of Tianjin University of Science and Technology, Tianjin, 300547, China, yfchen@tust.edu.cn.
authors.forename: Yefu
authors.initials: Y
authors.lastname: Chen
authors.forename: Feng
authors.initials: F
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Guo
authors.forename: Guangxin
authors.initials: G
authors.lastname: Liu
authors.forename: Xuewu
authors.initials: X
authors.lastname: Guo
authors.forename: Dongguang
authors.initials: D
authors.lastname: Xiao
mesh_terms: D000217:Acyltransferases / Q000235:genetics; D000434:Alcoholic Beverages; D002208:Caproates / Q000378:metabolism*; D002681:China; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D007218:Industrial Microbiology; D009812:Odorants; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics
chemical_list: D002208:Caproates; D029701:Saccharomyces cerevisiae Proteins; D000217:Acyltransferases; C000588861:EHT1 protein, S cerevisiae; D003066:Coenzyme A Ligases; C079237:ethyl hexanoate