Influence of steaming time during steam-explosion on the chemical composition, crystallinity and enzymatic hydrolysis of Lespedeza bicolor stalks.

The objective of this study is to evaluate the effects of steaming time on the shrub(Lespedeza bicolor)biomass treated by steam explosion.The chemical composition,crystallinity and enzymatic hydrolysis of the lignocellulosic residues were studied.The stalks were firstly steamed at 2.25 MPa for 2,3,4,5,6,10 min,respectively,and then exploded.The results showed that no significant differences in the content of cellulose and lignin were observed during the various steam explosion pretreatments,while the content of hemicelluloses was found to be decreased obviously.It was found that the crystallinity of cellulose in the residues was increased by 60.67%,probably due to the removal of amorphous district.The optimum enzymatic hydrolysis condition was found to be 46℃,60 hrs,80 U cellulase dosage and 5% substrate concentration,taking the raw material as substrate.It was also found that the steam explosion pretreatment effectively enhanced the enzymatic hydrolysis to 84%,which was about 2.8 times higher than the un-pretreated raw material by greatly improving the accessibility of cellulose.Therefore,it can be concluded that the steam explosion is an effective pretreatment process.