Effect of Furfural On Xylose Fermentation Using Saccharomyces Cerevisiae 424A (LNH-ST)

Furfural, the thermal degradation product of pentose sugars (xylose and arabinose), could be a significant inhibitor of the fermentation of lignocellulosic hydrolysates. In this study, we report the effect of furfural at various initial concentration (5, 7, and 10 g/L) on xylose and mixed sugar fermentation (xylose + glucose).  Furthermore, we examined these effects on fermentations with different initial cell mass concentrations of genetically modified glucose/xylose fermenting Saccharomyces cerevisiae 424A (LNH-ST).

Significant sugar utilization and cell growth did not start until the furfural in the medium was metabolized. Initial specific consumption rates (g ∙ h^-1 ∙ g _DW^-1) of glucose and xylose , after furfural was metabolized , decrease as initial furfural concentration increases. The impact of the furfural on xylose specific consumption rates was more severe than on glucose specific consumption rates, especially when xylose was only sugar present in the medium.  In mixed sugar fermentations, the furfural inhibition on xylose fermentation was substantial lower compared to fermentation of xylose alone. Generally, the specific consumption rate of glucose was several times (3 – 5) higher than the specific consumption rate of xylose under the same condition in presence of furfural.  Interestingly, the maximum specific growth rate decreased with increased initial cell mass concentrations.