Improvement of ethanol fermentation from lignocellulosic hydrolysates by the removal of inhibitors

In this study, the removal efficiency of fermentation inhibitors in a lignocellulosic hydrolysate by electrodialysis (ED) and the ethanol performance of ED-treated hydrolysate were investigated. The fermentable sugars and inhibitors concentrations in the hydrolysate differed significantly depending on the kind of biomass and acid catalysts. In the mixed hardwood, acetic acid and furfural in the hydrolysate were high as 8.41–8.57 g/L and 2.68–4.23 g/L, respectively, but 5-hydroxymethylfurfural (HMF) concentration was relatively low compared with that of mixed softwood. The ED process showed the high effectiveness for removing acetic acid and total phenolic compounds in the hydrolysate without loss of fermentable sugars. However, most of the HMF and furfural remained in the hydrolysate after ED. Ethanol fermentation was not completed in untreated and mixed hardwood ED-treated hydrolysates due to the high concentration of furfural. Meanwhile, ethanol fermentation was successfully performed in a mixed softwood ED-treated hydrolysate pretreated with dicarboxylic acid. The maximum ethanol concentration attained after fermentation with an initial fermentable sugar level of 27.78 g/L was 10.12 g/L after 48 h.