Abstract: The effects of by-products from acid hydrolysis of biomass, such as formic acid, acetic acid and furfural, on ethanol fermentation of thermotolerant Saccharomyces cerevisiae were studied. Results showed that the maximum inhibitor-tolerating mass concentrations of thermotolerant S.cerevisiae were formic acid 2.0g/L, acetic acid 5.0g/L and furfural 8.0g/L, respectively. Biomass yield and formic acid mass concentration( 0-3.0g/L)almost presented a linear relationship. Inhibition effect was decreased in the order of formic acid, acetic acid and furfural. To improve the ethanol yield of hydrolysate fermentation, inhibitor content should be minimized as much as possible, especially formic acid.

Key words: acid hydrolysis by-products, thermotolerant Saccharomyces cerevisiae, fuel ethanol