Efficient Hydrolysis Of Cellulose By Modified Cellulase In Ionic Liquid

Seven kinds of ionic liquids （ILs） were synthesized and characterized by FT-IR、1H-NMR and13C-NMR techniques. Among them,1-hydroxyethyl-3-methyl sulfonatedacetic acid salt （[C₂OHmim][OAc]） with excellent solubility for cellulose andbiocompatibility with cellulase was firstly reported. Cellulose and regeneratedcellulose from the ILs were investigated by X-ray, SEM, FT-IR and TG/DTA toanalysize the changing of the structure and morphology of cellulose. The results showthat regenerated cellulose is of loose structure, poor crystallinity and stability.Cellulase was modified by monomethoxyl-polyethylene glycol maleimide（molecular weight5k）（mPEG-MAL5k）, monomethoxyl-polyethylene glycolsuccinimide （molecular weight5k）（mPEG-SPA5k） and monomethoxyl-polyethyleneglycol aldehyde（molecular weight5k,10k,20k）（mPEG-ALD5k,10k,20k）,respectively. The obtained modified cellulose were labeled as Cell-ALD （5k,10k,20k），Cell-SPA5k and Cell-MAL5k. To obtain optimum conditions of modification,reaction temperature, reaction time, pH, concentration of cellulase and mass ratio ofmodifier and cellulase for Cell-ALD5k were investigated in detail. In addition, thestability and catalytic activity of modified cellulase was examined in[C₂OHmim][OAc], and the results show that their stability and catalytic activity wasimproved obviously in ionic liquids.Microcrystalline cellulose （MCC） is degradated in situ by the nature-cellulaseand five kinds of modified cellulase in MCC/[C₂OHmim][OAc] homogeneoussystem. The concentration of reducing sugar is characterized by DNS. The result showthat Cell-ALD5k is of optimum efficiency enzymatic activity, the quantity of reducingsugar was3.94mg/mL and the conversion was93.8%after24h in15%（w/v） [C₂OHmim][OAc]-buffer media.At the same time, in situ saccharification of naturecellulose, such as straw, filter and cotton was also investigated in15%（w/v）[C₂OHmim][OAc]-buffer media by Cell-ALD5k, the filter can be effectivelydegradated, and the conversion can reach93.8%after24h.MCC is degradated in situ by the cellulase and five kinds of modified cellulase inMCC/[Bmim]Cl（1-methyl-3-butyl sulfonated chlorine salt） homogeneous system.Theconcentration of reducing sugar is also characterized by DNS. The result show thatCell-ALD20k is of the optimum efficiency enzymatic activity in15%（w/v）[Bmim]Cl-buffer media, the quantity of reducing sugar was4.09mg/mL and the conversion was97.4%after24h. It is important that modified enzymes can still keep good stabilityand catalytic activity in [Bmim]Cl. At the same time, in situ saccharification of naturecellulose, such as straw, filter and cotton was also investigated in15%（w/v）[Bmim]Cl-buffer media by Cell-ALD20k, the cotton can be effectivelydegradated,and the conversion can reach97.0%after24h.