Highly Efficient Lignocellulose Pretreatment And ?-glucosidase Immobilization

The lack of an efficient pretreatment method and high enzyme usage are the two main factors those limit the large-scale commercial bioconversion of lignocellulose into fuel ethanol.In the dissertation,corncob was selected as raw material,while Fenton pretreatment,sequential Fenton and alkaline pretreatment was used to destroy biomass recalcitrance for improving the efficiency of enzymatic hydrolysis.Furthermore,the immobilization of ?-glucosidase was carried out to realize the recycling usage of enzyme for reducing enzyme cost.The major conclusions are listed as follows.(1)Fenton pretreatment of corncob: the effects of different pretreatment conditions,such as the concentration of H2O2 and FeCl2,pretreatment time,temperature and loading of biomass,to the compositions and efficiency of enzymatic hydrolysis of corncob were investigated.The pretreatment conditions were optimized as follows.When the concentration of H2O2 is 17.6 mmol/g substrate,the concentration of FeCl2 is 0.125 mmol/g substrate,0.5 h,40 oC and 5%(w/v),the glucose yield of pretreated corncob was 64.71%.The structural properties of untreated and pretreated corncob were characterized by scanning microscope(SEM),X-ray diffraction(XRD),BET surface area analyzer(BET)and Fourier infrared spectrum(FTIR).(2)Combined pretreatments(Fenton and alkaline pretreatments)of corncob: optimized process parameters and obtained the best pretreatment method,namely sequential Fenton and alkaline pretreatment.The glucose yield of pretreatment corncob that pretreated under the optimized conditions was 80.92%.(3)Immobilization of ?-glucosidase: Choosing core-shell magnetic silica as carrier,?-glucosidase was immobilized on carrier by the assistance of polydopamine.In this work,the effects of enzyme loadings,the concentration of dopamine and the immobilization time on enzyme activity and immobilization yield were systematically investigated.The immobilized ?-glucosidase enzyme activity can reach 25.01U/g when enzyme loading was 50U/g carrier,the concentration of dopamine was 1.6mg/mL and the immobilization time was 24 h.It is superior to the enzyme activity of ?-glucosidase immobilized by traditional glutaraldehyde crosslinking.