Effects of nitrogen supplementation on Saccharomyces cerevisiae JP14 fermentation for mead production

Abstract Honey must supplementation is necessary for mead production due to the deficiency in nitrogen materials in this feedstock, despite its high fermentative sugar content. The nitrogen limitation can halt or slow fermentation and lead to the production of unpleasant sensorial compounds, such as sulfur derivatives. The yeast JP14, a Saccharomyces cerevisiae isolated from Jataí bee’s pollen, was inoculated in 25 °Brix honey must with – 0 (control); 0,3; 0,7 and 1,0 g∙L-1 – of di-ammonium phosphate (DAP) and ammonium sulfate (AS). The addition of both supplements resulted in increased cell viability in the first 5 days of fermentation at 20 °C, but did not affect the final acidity of the produced meads. Supplementation also leads to increased sugar consumption, and sugar conversion into ethanol increased as nitrogen supplementation increased, especially with DAP. This indicates that these compounds also regulate yeast metabolic pathways. Supplementary nitrogen acts both in protein anabolism and the gene expression of glycolytic and fermentative pathway components, favoring, in this case, sugar conversion into ethanol. This is the first work describing how different DAP and AS concentrations influences mead production and showing the comparison between these two supplements.摘要 尽管蜂蜜醪液（honey must）具备较高的可发酵糖含量，但其氮源物质存在不足，因此在蜂蜜酒（mead）的生产中需要对其进行补氮处理。氮源限制会抑制或延缓发酵过程，并导致产生硫衍生物等不良感官风味物质。本研究将酵母JP14——一种从雅塔伊蜂花粉中分离得到的酿酒酵母（Saccharomyces cerevisiae）——接种至白利糖度为25°Brix的蜂蜜醪液中，分别添加0（对照组）、0.3、0.7和1.0 g·L⁻¹的磷酸氢二铵（DAP）与硫酸铵（AS）。两种补氮剂的添加均能在20℃发酵的前5天提升酵母细胞存活率，但对所制得蜂蜜酒的最终酸度无显著影响。补氮处理还能提升糖消耗速率，且随着氮源补加量的增加，糖向乙醇的转化效率也随之升高，其中磷酸氢二铵（DAP）的效果尤为显著。这表明上述两种补氮剂同样能够调控酵母的代谢通路。补加的氮源既参与蛋白质合成代谢，也能调控糖酵解与发酵通路相关组分的基因表达，从而在本研究体系中促进糖向乙醇的转化。本研究首次阐述了不同浓度的磷酸氢二铵（DAP）与硫酸铵（AS）对蜂蜜酒生产的影响，并对比了这两种补氮剂的应用效果。