Conversion Process Of Natural Cellulose With Ionic Liquid/Biocatalyst And Mechanism Reseach

Ionic liquid has good application potential as green solvents in conversion ofcellulose materials into bio-energy. However, ionic liquid suffers from someimportant aspects, such as cellulose material existence recrystallization, enzymecatalytic activity is not strong, ionic liquid recycling difficult problems, which lead tolow efficiency in ionic liquids involved biochemical process of cellulose conversion.To solve the problems, we studied ionic liquid/enzyme catalytic process, microbialcatalytic conversion and mechanism for production of bioenergy from cellulosicbiomass.Firstly, the ionic liquid (IL)1-ethyl-3-methylimidazolium hydrogen sulfate([EMIM][HSO4]),1-ethyl-3-methylimidazolium dimethyl phosphate ([EMIM][DMP])and1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) were synthetized usingone-step method. Then those ILs were mixed to pretreat cellulosic biomass. The resultindicated that viscosity of the mixed ionic liquids was reduced at the sametemperature. NMR and SEM data showed that crystallinity of straw was reduced afterpretreatment and cellulose backbone was broken.1-methyl-3-ethylimidazoliumdimethyl phosphate ([MEIM][DMP]) was used to treat cellulose with surfactant asadditive. The results showed that reducing sugar yield of regenerated cellulose with[MEIM][DMP]/PEG4000treatment after hydrolysis48h was6.5%higher than[MEIM][DMP] pretreatment. IR spectrum and XRD analysis showed that [MEIM][DMP]/PEG4000could decreased the degree of crystallinity.Secondly, the factors and optimum conditions of the degradation of mulberrypowder with cellulose and pectinase in AOT reverse micelles system were studied.The results showed that the hydrolysis rate of mulberry powder as raw material in thereverse micelle system was highest, and the optimum temperature was50℃, the pHwas8, the moisture content ωowas25. In this case, catalytic property of two enzymes(cellulase and pectinase) was the strongest, and the maximum conversion rate reached72.02%.Thirdly, microcrystalline cellulose was in situ fermentation after pretreatmentwith [MMIM][DMP]. Found that the ethanol was produced, And the analysis of[MMIM][DMP] in situ fermentation on cellulose with response surface, to get thebest conditions for the fermentation system pH4.8, the [MMIM][DMP] content of 9.67%, the reaction temperature was49.60℃. Under this condition, after48h, theyield of ethanol was1620mg/L, and the conversion rate was42.8%. Little effect onproduction of ethanol was found in-situ fermentation. So in-situ fermentation systemcould be used for ethanol production.Finally,[MMIM][DMP] was recycled by reverse micelle/aqueous two-phasecontinuous process. The result showed that the protein and carbohydrate could beeffective removed, thereby improving the purity of the recovered IL. The recoveryrate was92.3%at aqueous two-phase composition of18%sulfuric acid ammoniumand28%ethanol. IR showed the crystallinity of regenerate cellulose with recycled ILwas decreased as compared to untreated cellulose. So the reverse micelle/aqueoustwo-phase systems could be effectively recovered ionic liquid.In conclusion, ionic liquid/biological catalytic process for bioenergy productionfrom cellulosic biomass was established in this work. Moreover, the mechanism ofcellulose conversion process was illustrated using ionic liquid/enzyme, additives andmicrobial bioconversion.