Abstract:To increase the production of ethyl caproate by Chinese liquor yeast (S. cerevisiae AY15), shorten the fermentation period, and reduce the grainconsumption, a recombinant strain AY-PEK was constructed by overexpressing EHT1 (encoding ethanol hexanoyl transferase) to investigate the effect of EHT1-overexpression on the performance of ester-producing. The EHT1 gene was amplified from genomic DNA of AY15, the PGK1 promoter and resistance gene KanMX were orderly inserted into vector Yep352 to construct the expression plasmid Yep-PEK. Then EHT1-overexpression mutants AY-PEK were selected by YEPD agar plates containing 1400 μg/mL G418 after the plasmid Yep-PEK was transformed into AY15. The results showed that after liquid fermentation by corn, the differences in fermentation performances (growth rate, fermentation rate and the yield of alcohol) between AY-PEK and AY15were negligible. However, the production of ethyl caproate produced by AY-PEK was markedly increased to 2.21-fold as high as that of parental strain AY15. Ethyl octanoate and ethyl decanoate were improved by 31.4% and 49.1%, respectively. The same amount of caproic acid was added to fermentation medium to imitate the actual fermentation, the production of ethyl caproate produced by AY-PEK was increased to nearly 2-fold higher than that of AY15, and the amount of total esters were also increased by 32.2%. Overexpression of EHT1 gene can significantly enhance the production of ethyl esters, especially ethyl caproate.
