Studies Of Saccharification For The Grinding Wheel Pretreated Wheat Straw

In this study, wheat straw pretreated by grinding wheel without adding any chemicals was taken as raw material to study the effect of dilute acid hydrolysis and dilute alkaline pretreatment on it. Subsequently, this study investigated the enzymatic hydrolysis of alkali pretreated wheat strawThe results of dilute acid pretreatment indicate that dilute acid cannot catalyze cellulose into glucose a lot when temperature is low (100-125℃). However, most of hemicellulose can be hydrolyzed into monosaccharide in that condition. As the acid concentration, hydrolysis time and temperature raising, more and more cellulose and hemicellulose were converted into monosaccharide. But, the conversion yield of hemicellulose began to decrease when the condition was intensified. Because of amounts of xylose and glucose continued to be decomposed into furfural and HMF.The orthogonal analysis of dilute hydrochloric acid indicated that the maximum pentose yield of96.04%was obtained at this condition: hydrochloric acid concentration3%, temperature120℃,60min, solid loading1:25. The orthogonal analysis of dilute sulfuric acid indicated that the maximum pentose yield of94.25%was obtained at this condition:sulfuric acid concentration4%, temperature120℃,80min, solid loading1:25.The subsequent experiment of dilute alkaline pretreatment found that about40%hemicellulose and most of lignin can be effectively removed by dilute NaOH solution while there was little effect on cellulose. The NaOH concentration made an obvious effect on the removal of hemicellulose. It is suggested that low concentration should be adopted to reserve more hemicellulose. The temperature is the most important factor which affects the removal of lignin and83.33%of it can be removed at100℃with1%NaOH for1h.The subsequent experiments showed that the alkaline pretreatment substantially increased the digestibility of lignocellulose. The conversion of polysaccharide is positively correlated with the content of lignin in lignocellulose. It was extremely enhanced that the digestibility of wheat straw pretreated by the combination of grinding wheel pretreatment and alkaline pretreatment. The maximum polysaccharide conversion of98.47%and maximum monosaccharide concentration of53.5g/1can be obtained in the enzymatic hydrolysis process.