Fractionation Of Corn Stover And Chestnut Shell And Their High-value Biotransformation

Over the past century,increasing consumption of fossil energy results in energy crisis and environmental pollution,limiting the pace of human sustainable development.Lignocellulosic biomass is the most abundant and renewable material in the world for the production of biofuels.Using lignocellulosic biomass derived biofuels could reduce reliance on fossil fuels and contribute to climate change mitigation.To make lignocellulosic feedstock more effective enzymatic hydrolysis to fermentable sugars by cellulases,development of effective pretreatment process to increase the susceptibility of cellulose is essential to soften its tough assembled structure and increase its porosity.In this study,one pretreatment by combining acidified aqueous ionic liquid 1-butyl-3-methylimidazolium chloride solution with dilute NaOH extraction was employed to pretreat agricultural waste corn stover(CS)and another pretreatment by combining ethylene glycol-HClO4-water with dilute NaOH extraction was employed to pretreat forestry waste chestnut shell(CNS).Simultaneously,the ethanol fermentabilty of recovered hydrolyzates containing glucose was conducted with an ethanol producing strain S.cerevisiae.In addition,the cellulases of Galactomyces sp.CCZU11-1 were used for the enzymatic in situ saccharification of CNS in the IL [Mmim]DMP-water media.These results are given as follows:Firstly,a pretreatment by combining acidified aqueous ionic liquid 1-butyl-3-methylimidazolium chloride solution with dilute NaOH extraction was employed to pretreat CS.After NaOH(1 wt%)extraction at 90°C for 1 h,[Bmim]Cl-HCl-water(78.8: 1.2: 20,w/w/w)media was used for further pretreatment at 130°C for 30 min.After being enzymatically hydrolyzed for 72 h,corn stover pretreated could be biotransformed into reducing sugars in the yield of 95.1%.Furthermore,the recovered hydrolyzates obtained from the enzymatic hydrolysis of pretreated CS could be fermented into ethanol with the theoretical yield of 88.0%.Secondly,sequential ethylene glycol-HClO4-water(88.8: 1.2: 10,w/w/w)pretreatment at 130°C for 30 min and dilute NaOH(1 wt%)extraction at 90°C for 1 h was firstly employed to pretreat CNS.It was found that the pretreated CNS could be effectively saccharified.After 72 h,the reducing sugars and glucose from the hydrolysis of 50 g/L pretreated CNS by a cocktail of enzymes could beobtained at 77.8% and 65.4% yield,respectively.Finally,the recovered hydrolyzates containing glucose could be fermented into ethanol with the theoretical yield of 86.1%.Finally,it was the first time to report that the cellulases of Galactomyces sp.CCZU11-1 showed high activity and stability in the culture and reaction media containing IL [Mmim]DMP.Using untreated CNS as carbon source in the culture media containing IL [Mmim]DMP(5%,w/v),high activity of FPA(28.6 U/mL),xylanase(186.2 U/mL),and CMCase(107.3 U/mL)were obtained,and 184.9 mg/L of total protein was achieved.Furthermore,the changes in the structural features(crystallinity,morphology,and porosity)of the solid residue of CNS utilized with Galactomyces sp.CCZU11-1 were characterized with FTIR,SEM,and XRD.After was enzymatically hydrolyzed with the prepared crude enzymes in IL [Mmim]DMP diluted to 20%(w/v),a high yield of reducing sugars was obtained at 62.1%.In summary,efficient pretreatment systems were established to realize the high utilization of lignocellulose in this study.Galactomyces sp.CCZU11-1 was employed to produce high IL-tolerant cellulase and a compatible IL-cellulase system was developed for the efficient in situ saccharification of CNS.In short,the combination pretreatment strategies show high potential application in future and the cellulases from Galactomyces sp.CCZU11-1 have high potential for efficient in situ saccharification of lignocellulosic materials.