Chunyun Qu,Jianjun Li,Fuxin Liu,Yu Zeng,Yiyin Xu,Weidong Bai,Hao Dong,Gongliang Liu
To diversify the aromas and enhance the quality of fruit wines, Zygosaccharomyces mellis LGL-1 (LGL-1), as a non-conventional yeast, was applied for fruit winemaking along with biochar facilitating the fermentation. Results demonstrated that LGL-1 exhibited higher synthesis of ethanol and esters compared to the commercial winemaking yeast CV171 during wampee/grape/litchi winemaking. Intriguingly, the main esters produced by LGL-1 were quite different from those of CV171, resulting in diverse flavors. Four kinds of food-grade biochar were applied to facilitate the fermentation of LGL-1 under the mimic solution of fruit juice (MSM medium) respectively, and results showed that the coconut shell granule biochar (G2) was the best choice with both substrate consumption and product formation improved significantly, especially with esters enhanced by 357.87%, owing to the reduced oxidation-reduction potential, improved intracellular ratio of NADH/NAD + and enhanced activities of esterase. When applied for wampee/grape/litchi winemaking, G2 could also facilitate the fermentation of LGL-1 with total content of esters in each wine improved by 173.7%, 71.8% and 44%. The total concentration of higher alcohols in wampee/grape wine was enhanced by 35.6% and 21.1%, but unchanged significantly in litchi wine. The content of total organic acids in grape wine and litchi wine was changed insignificantly but decreased by 16.7% in wampee wine, which might not affect the flavor based on the taste threshold of organic acids. Data above indicated that LGL-1 is a potential candidate for fruit winemaking, and the fermentation fortified by G2 is a promising method for improved aromas of fruit wine.
Chunyun Qu,Zuyue Qi,Shuochun Lin,Jianjun Li,Yu Zeng,Yiyin Xu,Weidong Bai,Gongliang Liu
For wine, higher alcohols are double-edged swords, which benefit flavors in appropriate amount but cause negative effects on aromas as well as side-effects for consumers in excessive amount. In this study, five kinds of ammonium salts were tested to reduce higher alcohols produced by Zygosaccharomyces mellis LGL-1 (LGL-1), among which, (NH 4 ) 2 HPO 4 exhibited most excellent effects with higher alcohols reduced by 32.79%. Both NH 4 + and HPO 4 2- demonstrated individual capacities to reduce higher alcohol levels and transcriptome analysis was employed to investigate the synergistic mechanism. Results showed that both NH 4 + and HPO 4 2- could regulate higher alcohol biosynthesis, but with different regulators, Cat8 for the synergistic effect of NH 4 + and HPO 4 2- , and Ino80 for HPO 4 2- specifically. Meanwhile, HPO 4 2- reduced the activity of BCAT2, specifically and NH 4 + increased the activity of BCAT1 particularly, the combination of which led to the reduction of higher alcohol biosynthesis. Both Gtr1 and TorC1 were downregulated with HPO 4 2- or NH 4 + addition, with more pronounced downregulations under their combination. Collectively, the synergistic effects of ammonium and phosphorus on higher alcohol biosynthesis in LGL-1 were existed. To amplify this effect, the molar ratio of nitrogen to phosphorus was optimized and a mole ratio of 1:1 was applied for Wampee/Grape winemaking with higher alcohols reduced by 24.99%-26.76% but with the content of ethanol, esters and organic acid unchanged significantly. Data above suggested that the combined addition of NH 4 + and HPO 4 2- could play synergistic effects on higher alcohol biosynthesis, which was an effective strategy to reduce higher alcohols in wines for improved qualities.
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