The effect of alkaline extraction of hemicellulose on cocksfoot grass enzymatic hydrolysis recalcitrance

Abstract

In order to verify the inhibitory influence of hemicellulosic structure and content on the enzymatic hydrolysis of cellulose from cocksfoot grass for bioethanol production, the fractional isolation and structural characterization of hemicelluloses and cellulose-rich substrates from the delignified cocksfoot grass was studied in detail. The results showed that the removal of hemicelluloses by alkaline treatments can greatly improve the enzymatic hydrolysis efficiency of cellulose in cocksfoot grass. As compared with the enzymatic hydrolysis yield (74.3%) and crystallinity index (30.5%) of the delignified cocksfoot grass (consisting mainly of cellulose and hemicelluloses), the enzymatic hydrolysis yields and crystallinity indexes of the four cellulose-rich substrates increased to 90.3–95.1% and 37.3–43.7%, respectively, due to the partial removal of hemicelluloses and some amounts of amorphous cellulose by alkaline treatments. Besides, the hemicellulosic fractions extracted with aqueous NaOH and KOH solutions from the delignified cocksfoot grass exhibited similar structures, which were composed of ʟ-arabino-(4-O-methyl-ᴅ-glucurono)xylans, galactoarabinoxylans, and β-glucans.