Investigation On The Pretreatment Of Sugarcane Bagasse By NaOH And Ionic Liquids And Its Characteristics Of Enzymo-Lysis And Fermentation

Sugarcane bagasse (SCB) is one of the major byproducts of the sugar industry. It hasbeen an important renewable biomass resource due to its wide variety of sources and highcontent of homocellulose. It can be used as a raw material to produce biofuels, such as ethanol,after appropriate pretreatment to overcome its recalcitrance and improve enzymatic conver-sion. In this study, we established the NaOH and ionic liquids (ILs) pretreatment process andevaluated the fermentability of the pretreated SCB by co-fermentation simultaneous sacchari-fication fermentation (SScF).The main chemical compositions of SCB were measured as follows:38.63%glucan,24.1%xylan,21.34%Klason lignin,3.09%acid soluble lignin,1.91%benzene-ethanol ex-tractives, and1.79%ash. NaOH pretreatment studies showed the pretreatment temperature,time and NaOH concentration significantly affected the emzymolysis and fermentation effi-ciency of the pretreated SCB. Three factors and three levels of orthogonal experiment showedthat the optimal conditions for NaOH pretreatment were: NaOH concentration of4.5%, timeof11h, and the temperature of85oC. Compared with the raw SCB, the glucan content of thepretreated SCB increased by46.16%, however, xylan and Klason lignin decreased by15.77%and72.87%, respectively.Different ILs was evaluated on the pretreatment of SCB. Results showed that [Emim]Acwas the optimum IL for SCB pretreatment. The pretreatment temperature had significant ef-fect on the solubility of SCB and enzymatic conversion of pretreated SCB. The solubility ofSCB in [Emim]Ac was increased with increasing temperature, and3%SCB could be dis-solved completely when the temperature reached140oC. The regenerated bagasse from the[Emim]Ac pretreatment (140oC,0.5h) exhibited enhanced enzymatic digestibility with anefficiency of64.99%after24h hydrolysis. Compared with the untreated SCB, the glucancontent of the pretreated SCB increased by61.6%, xylan and Klason lignin decreased by6.9%and52.6%, respectively. The results of X-Ray Diffraction (XRD) and Fourier TransformInfrared Spectroscopy (FTIR) indicated that crystallinity index (CrI) decreased from41.65%(untreated SCB) to18.74%([Emim]Ac-treated SCB) and the crystal structure was trans-formed from cellulose I to cellulose II. The initial saccharification rate increased with de-creasing CrI, and negatively correlated with the CrI.Fermentability of the pretreated SCB was evaluated by using simultaneous saccharifica-tion and co-fermentation (SScF) and separate hydrolysis and fermentation (SHF). The resultsshowed that according to fermentation efficiency NaOH pretreatment was more suitable for SCB pretreatment and the SHF process was much better than SScF process for ethanol pro-duction from sugarcane bagasse.