Investigation On The Pretreatment Of Sugarcane Bagasse By Mild Alkaline Coupled With Ionic Liquid And Evaluation Of Ethanol Fermentability Of The Pretreated Sugarcane Bagasse

Sugarcane bagasse （SCB） is the major byproduct of the sugar industry. As its widevariety of sources and high holocellulose content, it becomes an important renewable biomassresource. It can be used as a raw material to produce ethanol after appropriate pretreatment. Inour study, it established the SCB combination pretreatment of ionic liquid （IL） based on mildalkali pretreatment （NH₄OH-H₂O₂mixture）. Meanwhile, the ethanol production process ofsimultaneous saccharification and co-fermentation simultaneous saccharification fermentation（SScF） and separate hydrolysis and fermentation （SHF） were used to evaluate theperformance of ethanol fermentation.The main chemical composition of SCB was measured as follows （dried basis）:39.50%glucan,19.77%xylan,2.02%arabian,21.04%klason lignin,4.89%acid soluble lignin,5.69%ash and2.55%benzene-ethanol extractives. Pretreatment studies have shown that theNH₄OH-H₂O₂concentration and liquid-solid ratio affected the fermentation efficiencysignificantly. Response surface methodology （RSM） is successfully applied to optimize mildalkali pretreatment conditions, and the optimum pretreatment conditions were: NH₄OH-H₂O₂concentration of53%, liquid to solid ratio of28and the temperature of63°C. The glucancontent increased by27.6%, as well as the content of xylan, arabian, klason lignin, acidsoluble lignin and benzene-ethanol extractives decreased by6.1%,30.7%,49.2%,35.8%and55.3%, respectively, under the optimized conditions after NH₄OH-H₂O₂pretreatment.Study was carried on ILs coupled with NH₄OH-H₂O₂pretreatment of SCB. Theregenerated bagasse from the combined pretreatment （[Amim]Cl at100°C for1h） exhibitedsignificantly enhanced enzymatic digestibility with a cellulose recovery of85.81%and anefficiency of91.42%after12h of hydrolysis. X-ray diffraction （XRD） and Fourier transforminfrared spectroscopy （FTIR） showed that the cellulose crystallinity decreased after ILcombined pretreatment. It observed that crystallinity index （CrI） decreased from38.89（un-pretreated） to20.81（combined pretreated）. The glucan content increased by38..2%whileth xylan and klason lignin content decreased by3.7%and62.2%as compared to un-pretreatedSCB. The regenerated bagasse was also employed in SScF for ethanol production with the fermentation efficiency as high as94.51%, and the similarity of the fermentation curvesindicated that the pretreatment by [Amim]Cl had no adverse effects in the following-upfermentation.Investigation was also carried on SHF and SScF process. The enzymatic efficiencyincreased with the increase of temperature and the amount of enzyme as well as the decreaseof substrate loadings under certain conditions in the process of enzymatic hydrolysis of SCB.Three factors and four levels of orthogonal experiment showed that the optimal conditions forenzymatic hydrolysis were: enzyme dosage of25FPU/g bagasse, the temperature of50°C,the initial pH of4.9. The bagasse hydrolyzate was suitable for yeast growth and ethanolfermentation by adding certain nutrients, and the fermentation efficiency was82.70%with anethanol yield of0.48g/g at96h. The initial pH value, the amount of enzyme, inoculum size,substrate loading and temperature affected the fermentation efficiency of SScF, in which theamount of enzyme and substrate concentration affected significantly.