The reduced yields of acetaldehyde and fusel alcohols through fermentation by Saccharomyces cerevisiae is of significance for the improvement of the flavor and health of alcoholic beverages. In this study, the ADH2 (encode alcohol dehydrogenase) and THI3 (encode decarboxylase) genes of the industrial diploid strain S. cerevisiae XF1 were deleted. Results showed that single-gene-deletion mutants by separate gene deletion of ADH2 or THI3 led to a reduced production of the acetaldehyde or fusel alcohols, respectively. In the meantime, the double-gene-deletion mutant S. cerevisiae XF1-AT was constructed by deleting the ADH2 and THI3 simultaneously. An equivalent level of the ethanol production by the S. cerevisiae XF1-AT could be achieved but with the yields of acetaldehyde, isoamyl alcohol and iso-butanol reduced by 42.09%, 15.65% and 20.16%, respectively. In addition, there was no interaction between the ADH2 deletion and THI3 deletion in reducing the production of acetaldehyde and fusel alcohols. The engineered S. cerevisiae XF1-AT provided a new strategy to alcoholic beverages brewing industry for reducing the production of acetaldehyde as well as the fusel alcohols.
Qiong Wu,Xiaoya Tao,Xinzi Ai,Zisheng Luo,Linchun Mao,Tiejin Ying,Li Li
Fruit aroma development depends on ripening. Abscisic acid (ABA) has been reported to be involved in the regulation of tomato fruit ripening . In the present study, the effects of exogenous ABA on aromatic volatiles in tomato fruit during postharvest ripening were studied. The results showed that exogenous ABA accelerated color development and ethylene production as well as the accumulation of carotenoids , total phenolics and linoleic acid in tomato fruit during ripening. Moreover, exogenous ABA increased the accumulation of volatile compounds such as 1-peten-3-one (2.06-fold), β-damascenone (1.64-fold), benzaldehyde (3.29-fold) and benzyl cyanide (4.15-fold); induced the expression of key genes implicated in the biosynthesis pathways of aromatic volatiles, including TomloxC , HPL , ADH2 , LeCCD1B and SlBCAT1 (the values of the log 2 fold changes ranged from −3.02 to 2.97); and promoted the activities of lipoxygenase (LOX), hydroperoxide lyase (HPL) and alcohol dehydrogenase (ADH). In addition, the results of promoter analyses revealed that cis -acting elements involved in ABA responsiveness (ABREs) exist in 8 of the 12 key genes involved in volatile biosynthesis, suggesting that ABA potentially affects aromatic volatile emissions via the regulation of gene expression profiles.
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