Figure 2

Comparison of the quantum dot (QD) method versus a more traditional microsatellite (MS) method when quantifying multiple yeast strains in mixed culture fermentations.

(a) There were no significant differences between cell growth (p = 0.70) or sugar utilization kinetics (p = 0.78) when comparing fermentations incubated with QD-GSH versus those without (based on ANCOVAs). These data suggest that the QD-GSH was non-toxic to the yeast throughout the entire course of fermentation. (b) Moreover, there was a positive and strong correlation between the QD and the MS method across all ratios and time points (R = 0.87). To visually display these results, this data is presented as a linear regression (r² = 0.76 and p = 0.003). Individual data points are RC212:D254 ratios of cell numbers. Although similar trends were exhibited in data sets from both the (c) MS and (d) QD method, there was significantly greater variability in the MS results (based on average standard error); albeit only a marginal significance across all fermentation stages (p = 0.07). Significant differences between ratio treatments were determined using a one-way ANOVA (p < 0.05). Values with the same letters at a given fermentation stage are not significantly different according to a Spearman rank test. Values are means ± S.E; ^dn = 3, 20 yeast cells analyzed per flask per time point; ^en = 3, >1600 yeast cells analyzed per flask per time point.