Effect of Extractives on Digestibility of Cellulose in Corn Stover with Liquid Hot Water Pretreatment

Many herbaceous lignocelluloses suitable for ethanol production have high extractives contents, such as some straws and corn stover. The high extractives content might affect pretreatment or enzymatic hydrolysis. In this study, extractives were removed from corn stover, and then extractives-free corn stover and ordinary corn stover were respectively pretreated using a liquid hot water (LHW) method and hydrolyzed to evaluate the effect of extractives on cellulose digestibility. Extractives-free corn stover presented higher cellulose digestibility than ordinary corn stover after the same pretreatment conditions. A total of 87.3% of cellulose was digested in extractives-free corn stover, compared to 71.0% in ordinary corn stover, after pretreatment at 200 °C for 20 min. It is speculated that some water-soluble extractives could buffer H+ ions from water and acetic acid during LHW pretreatment process, reducing xylan removal. Another reason for these results might be that some extractives could condense on corn stover after LHW pretreatment, which hinders cellulose hydrolysis.