Inhibition effects of furfural on aerobic batch cultivation of Saccharomyces cerevisiae growing on ethanol and/or acetic acid

Physiological effects of furfural on Saccharomyces cerevisiae growing on et hanol (15 g.l(-1)) or acetate (20 g.l(-1)) as the carbon and energy source were investigated. Furfural (4 g.l(-1)) which was added during the exponent ial growth phase in batch cultures, was found to strongly inhibit cell grow th on both carbon sources. No biomass formation occurred in the presence of furfural. However, furfural was in both cases converted to furfur;FI alcoh ol and furoic acid, and growth resumed after complete conversion of furfura l. During growth on ethanol, a rapid initial conversion of furfural to furf uryl alcohol was observed during the first few minutes after the addition o f furfural, after which the conversion rate decreased to approximately 0.15 g.g(-1).h(-1) for the remaining conversion time. Acetaldehyde accumulated in the medium during the first few hours of conversion. Interestingly, addi tion of acetate after furfural addition resulted in an increased conversion rate of furfural and a higher carbon dioxide evolution rate, but no growth was observed until after complete conversion of furfural. Furfural additio n to cells growing on acetate as the sole carbon source induced no formatio n of acetaldehyde, and the furfural conversion rate was lower than that on ethanol. The relationship between inhibition effects of furfural and NADH c onsumption is discussed.