EFFECTS OF LIGNOCELLULOSE DEGRADATION PRODUCTS ON ETHANOL FERMENTATIONS OF GLUCOSE AND XYLOSE BY SACCHAROMYCES-CEREVISIAE, ZYMOMONAS-MOBILIS, PICHIA-STIPITIS, AND CANDIDA-SHEHATAE

The inhibitory effects of six lignocellulose degradation products on g lucose fermentation by Saccharomyces cerevisiae and Zymomonas mobilis on xylose fermentation by Pichia stipitis and Candida shehatae were st udied in batch cultures. Toxic compounds were added in varying concent rations and subsequent inhibitions on growth and ethanol production we re quantified. Vanillin was shown to be a strong inhibitor of both gro wth and ethanol production by xylase fermenting yeasts and S. cerevisi ae when it was added to the culture media at a concentration of 1 g l( -1). Fermentative activities of Z. mobilis were greatly sensitive to t he presence of hydroxybenzaldehyde (0.5 g l(-1)). Analysis of culture media extracts showed that some of the inhibitors, particularly vanill in and furaldehyde, could be assimilated by the tested microbial strai ns which resulted in the partial recovery in both growth and ethanol p roduction processes on prolonged incubation.