Pretreatment Of Giant Reed With The Ammonia/Hydrogen Peroxide Method To Enhance Enzymatic Hydrolysis

Energy crisis requires the development of renewable energy that can displace fossil fuels. Bioethanol production from lignocellulosic biomass has become a hot global topic since lignocellulosic biomass is the most promising feedstock for biofuels production. The bioconversion of lignocellulosic biomass to bioethanol consists of three main steps: pretreatment, enzymatic hydrolysis and fermentation. The main effects of pretreatment are to disrupt recalcitrant crystalline structure, remove lignin and/or hemicellulose, and thus to improve the enzyme accessibility and catalytic efficiency.A novel pretreatment method, liquid ammonia treatment with(LATH) or without(LAT) hydrogen peroxide presoaking, was proposed in this paper for giant reed(Arundo donax. L). This study could provide theory basis for development of new pretreatment for lignocelluloses, and promote the fundamental research for cellulosic ethanol production.The main contents and conclusions were as follows:(1) The optimization of LAT pretreatment paremeters of giant reed was used response surface method(RSM). The results showed that the temperature and ammonia loading had a significant influence on polysaccharide conversion. The maximum glucan and xylan conversion rates were 96.47% and 83.72% respectively, which obtained at 170℃,0.82 water loading, 5.0 ammonia loading for 9.57 min and enzymatic hydrolysis 72 h. The total fermentable monosaccharide released was 538.12 g per 1000 g raw dry biomass.(2) Based on the optimal LAT conditions(130℃, water loading 0.4,ammonia loading 2.0 and residence time 10min), the effects of hydrogen peroxide loading on LATH were assessed. The results illustrated that LATH could effectively increase the glucan and xylan digestion rate. The highest total sugar yield of HP(Hydrogen peroxide treatment), LAT and LATH were 241.12 g, 495.74 g and 536.77 g, respectively, which enhanced by 25.55%, 158.13% and 179.49% compared with those of raw material. LAT and LATH had a certain application prospect.(3) The physical and chemical characteristics of LATH-treated giant reed were analysed using SEM, XRD and FTIR. The results showed that the fiber structure was destroyed, some crystalline region were turned to amorphous region, the hydrogen bonding of cellulose and lignin carbohydrate complex ester bonding connection were broken after LATH pretreatment. As a result, these changes effectively reduced the biomass recalcitrance of giant reed and promoted enzymatic hydrolysis.(4) Under the condition of 130 ℃, water loading 0.4, ammonia loading 2.0, and residence time 10 min, giant reed and miscanthus obtainded the highest enzymatic hydrolysis conversion with 0.5 H2O2 loading, while bamboo was happened at H2O2 loading of 1.0. The total sugar yields of giant reed, bamboo, and miscanthus under their optimal pretreatment conditions and enzymolysis 72 h were 536.77 g, 386.26 g, 550.15 g respectively, which were 2.58, 4.25, 3.44 times comparing with those of raw material. As a result, the pretreatment of LATH could effectively reduce the biomass recalcitrance of herbaceous plant and promote enzymatic hydrolysis.