A comparison of different pre-extraction methods followed by steam pretreatment of bamboo to improve the enzymatic digestibility and ethanol production

Abstract

In this work, investigation of pre-extraction of bamboo under three different conditions (alkaline, neutral, and acidic) prior to acid catalyzed (AC) steam pretreatment on the conversion of polysaccharides into fermentable sugars and ethanol was reported. Pre-extraction process was demonstrated to significantly improve the enzymatic digestibility of bamboo and reduce the formation of inhibitory compounds for fermentation. Comparing to the pre-extraction of bamboo under neutral and acidic conditions, alkaline pre-extraction of bamboo yielded the highest monomeric sugar yields following enzymatic hydrolysis, which were approximately 86% of glucose and 82% of xylose (based on the initial sugar composition). The fermentation of sugars released during enzymatic hydrolysis with pentose-hexose fermenting Saccharomyces cerevisiae Lg8-1 strain achieved the final ethanol concentrations of 50.1, 46.3, and 49.0 g/L, corresponding to the ethanol yields of 70.5%, 68.9%, and 65.1% (based on theoretical ethanol yield of the initial bamboo) for the prep-extraction of bamboo under alkaline, neutral, and acidic conditions, respectively. The results indicate that the pre-extraction of extractives and ash followed by AC steam pretreatment is a promising approach to improve the bioconversion of bamboo biomass to biofuels.