Study On Bioconversion And Utilization Of Lignocellulosic Biomass

Advancement in industrial biotechnology offers potential opportunities for economic utilization of agro-industrial residues such as sugarcane bagasse.Due to its abundant availability,it can serve as an ideal substrate for ethanol production.Ethanol can be produced from sugarcane bagasse using dilute sulfuric acid pretreatment followed by enzymatic hydrolysis and fermentation.The optimal condition for pretreatment is:2%sulfuric acid concentration,1:3(g dry biomass/mL acid) acid loading,reaction time 20 min,and reaction temperature 125℃.Under these conditions,the yield of reducing sugar reaches 31.57%.Scanning electron microscope(SEM) analysis shows that the structure and the surface of the bagasse were deformed and its fibers exposed by the pretreatment that is in favor of the subsequent enzymatic hydrolysis.The mixture pretreatment uses 2%dilute sulfuric acid and 2.5%sodium hydroxide to pretreat bagasse.Then the different samples were mixed together completely. Cellulase could directly hydrolysis the mixture.The ethanol concentration in the fermentation is 6.82 g/L.Cellulase production was carried out by solid state fermentation using sugarcane bagasse.The optimal condition for cellulase production is water content 75%, sugarcane bagasse and bran(1:1),at 30℃for 3 d.Under these conditions,cellulase activity(FPA) reaches 32.5 IU/g.When the cellulase dosage was above 15.0 IU/g substrate,the reducing sugar concentration attained 74.19 g/L under the optimal conditions(substrate concentration 15%,hydrolysis at 50℃for 30 h).A.glaucus EU7-22 could grow in sugarcane bagasse and produce complete cellulase system.Endoglucanase(EG),xylanase andβ-glucosidase(BG) are purified to apparent homogeneity from the culture supematant by ammonium sulfate precipitation(80%,w/v),Phenyl 6 Fast Flow(high sub) column chromatography and Sephacryl S-200 column chromatography.Molecular weights are determined as 27.0 kD,42.6 kD and 56.2 kD by SDS-PAGE,respectively.The purified EG(specific activity 15.92 IU/mg protein) is a monomeric protein.The optimum temperature is at 50℃.At pH 3.0,the purified enzyme was highly stable.The optimal temperature for the action of xylanase(specific activity 83.75 IU/mg protein) and BG(specific activity 5.10 IU/mg protein) were 65℃and 70℃,respectively.The purified xylanase and BG were highly stable at pH 5.0.