基于二次发酵糖代谢曲线下面积法对高浓度酒精发酵后期酵母发酵活力的评估

Evaluation of yeast vitality during the stationary phase of very high gravity ethanol fermentation based on area under the curve of sugar secondary fermentation

在主发酵过程的36、42、48、54与60 h取样离心,得到酵母细胞并等量地接入新鲜发酵培养基中进行二次发酵。测定酵母在二次发酵过程中糖代谢曲线并用Graphpad Prism 5软件计算糖代谢曲线下面积(AUC)来定量地表示酵母的发酵活力大小(糖消耗越快,糖代谢曲线下面积值越小,说明酵母的发酵活力越强)。结果表明,主发酵36、42、48、54与60 h酵母糖代谢能力逐渐下降,二次发酵AUC值分别是5 051、5 437、5 912、6 757与7 489,说明随着时间的推移主发酵后期酵母细胞的发酵活力逐渐下降;二次发酵参数分析也表明,AUC能够定量地表示主发酵后期酵母细胞的发酵活力大小,细胞发酵活力越强,AUC值越小,反之亦然。

Vitality of fermentation yeast is one of the key factors of very high gravity ethanol fermentation and it is essential to accurately and quantitatively determine the vitality of fermentation yeast. In this study,the same amount of yeast cell was harvested by centrifuging cultures at 36,42,48,54 and 60 h during the primary ethanol fermentation and transferred into fresh fermentation medium for secondary fermentation,respectively. By the software graphpad prism 5,the curve of sugar metabolism was plotted during the secondary fermentation and the area under the curve( AUC) of sugar metabolism was calculated. And then the AUC was evaluated quantitatively as a measure of yeast vitality( the faster sugar consumption- the less AUC indicating that yeast vitality is stronger; vice versa). The results indicated that the ability of sugar metabolism of yeast cell from culture at 36,42,48,54 and 60 h during the primary fermentation gradually decreased and the AUC was 5 051,5 437,5 912,6 757 and 7 489,respectively,indicating that the vitality of yeast cell from the stationary phase of primary fermeantion gradually decreased as the time went on.By secondary fermentation parameter analysis,the results also showed that yeast vitality could be evaluated quantitatively based on the AUC,namely,the less AUC,the stronger yeast vitality,vice versa.