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 由于蜂蜜醪液虽富含可发酵糖，但氮源物质匮乏，因此在蜂蜜酒（mead）生产中需对其进行氮源补充。氮源限制会抑制或减缓发酵过程，并导致产生硫衍生物等不良感官风味物质。本研究使用的酵母JP14为从雅塔伊（Jataí）蜂花粉中分离得到的酿酒酵母（Saccharomyces cerevisiae），将其接种于糖度为25 °Brix的蜂蜜醪液中，分别设置添加0（对照组）、0.3、0.7和1.0 g∙L⁻¹的磷酸二铵（di-ammonium phosphate, DAP）与硫酸铵（ammonium sulfate, AS）的实验组。在20℃下发酵的前5天内，添加两种氮源补剂均能提升酵母细胞活性，但对所制得蜂蜜酒的最终酸度无显著影响。氮源补充还可提升糖消耗速率，且随着氮源添加量升高，糖向乙醇的转化效率随之提升，其中以磷酸二铵组的效果尤为显著。这表明两类氮源补剂可调控酵母的代谢通路。补充氮源同时作用于蛋白质合成代谢，以及糖酵解与发酵通路相关组分的基因表达，从而在本实验条件下促进糖向乙醇的转化。本研究首次探讨了不同浓度磷酸二铵与硫酸铵对蜂蜜酒生产的影响，并对比了这两种氮源补剂的应用效果。