Research On Pretreatment And Enzymatic Hydrolysis Of Lignocellulose In Green Solvent

With the rapid development of global economy, bio-refining technology with lignocellulose as raw materials is one of the effective ways to solve the problems of resources and environments, so many countries are shifting their focus on large-scale development and utilization of clean energy from renewable resources. Corn stover and rice husk are by-product from agriculture, and they are large available, especially in China. Because of their rich in cellulose, hemicellulose and lignin, and they can be regarded as important biomass to produce valuable chemicals. Carbohydrates derived from lignocelluloses, can be converted into renewable energy products, such as bioethanol, biobutanol and biodiesel. Therefore, looking for green and efficient pretreatment methods, improving the efficiency of enzymatic hydrolysis will have a significance to reduce the cost of microbial lipid and the sustainable development of human society.In this paper, firstly, corn stover as the experimental materials, studied the effect of CO2pressure on pretreatment of corn stover in green solution which is composed of CO2、H2O and H2O2. In order to test the results of each pretreatment of CO2pressure, the effect of different pressure on the enzymolysis of pretreating solid and pretreating solution were investigated. It was found that pretreatment was most effective and the recovery of corn stover (dry weight) was30%, when the CO2pressure was4MPa. And the effect of different CO2pressure on the enzymolysis is great. After24hours enzymolysis, there were389mg/g and266mg/g total reducing sugar in the enzymatic hydrolysate of pretreating solution and pretreating solid, respectively.Next, according to the composition of rice husk, we investigated the pretreatment of rice husk in mixed orgnic electrolytes of1-ethyl-3-methyl-imidazolium Acetate (EmimAc)/N-Methylpyrrolidone (NMP)(XIL=0.2). After enzymatic hydrolysis, fermentable sugars、microbial liquid and nano silica could be obtained. This method developed a new way for the integrated utilization of rice husk. It was found that10wt%of rice husk can be dissolved in180min at140℃. This dissolution was associated with the full transformation of cellulose Ⅰ to cellulose Ⅱ in the rice husk, significant delignification. All of these physicochemical changes lead to an enhanced subsequent enzymatic saccharification of rice husk, and a total reducing sugars (TRS) yield of0.64g/g, and a glucose yield of0.34g/g were obtained. The solution from enzymatic hydrolysis was concentrated, then R.toruloides Y4yeast was used to ferment sugars to lipid for100hours, the lipid yield was9.2%and lipid content was32.5%. The residuals after the enzymatic hydrolysis are determined to be good source for the production of new silica material, and it was found that the nano silica particle prepared through pyrolysis at600℃for3h were uniform, spherical powder with a particle size around150nm,179.3m2/g of surface area.