Studies Of Enzymatic Hydrolysis Of Lignocelluloses By Cellulase

This study was mainly on the pretreatment and enzymatic hydrolysis of lignocellulose (cassava and sweet sorghum bagasse), to find a solution for the ethanol production from cellulose.For the enzymatic hydrolysis of cassava bagasse, by the pretreatment of 1% sulfuric acid at 120℃for 30-60min, the conversions of cellulose from three different pretreated cassava bagasse evaluated by enzymatic saccharification were about 80%, which were substantially higher than that of untreated bagasse (62%). For the enzymatic hydrolysis of cassava bagasse with high solid loading, fed-batch enzymatic hydrolysis can reduce the product inhibition. Finally, Fed-batch hydrolysis with enzymes addition at three times was recommended for high solid loading (25%) hydrolysis. In this condition, the cellulose conversion reached 84%, the concentrations of glucose and xylose reached 39.5 g/L and 7.8 g/L, respectively.For enzymatic hydrolysis of sweet bagasse, the study found that 120℃dilute acid pretreatment increased cellulose conversion slightly. When the temperature of dilute acid pretreatment increased to 150-180℃, the hemi-cellulose of sweet sorghum bagasse decreased to 2%, and the surface of bagasse present a large number of micro-holes. When the temperature of dilute acid pretreatment was 180℃, the cellulose conversion of sweet sorghum bagasse reached 50%, and the glucose concentration reached 25 g/L, which increased by 33% and 95% compared with that of untreated sweet sorghumbagasse, respectively. Effect of pretreated temperature on enzymatic hydrolysis of sweet sorghum bagasse catalytic was obvious.The impact of four pretreatment (ionic liquids, steam explosion, lime treatment and high-temperature dilute acid pretreatment) on cellulose structure shows that:steam explosion pretreatment showed significant improvement on enzymatic hydrolysis of bagasse. The cellulose conversion reached 70%, which 2.5 folds than the result of enzymatic hydrolysis of untreated bagasse. SEM photographs showed that after pretreatment, the sweet sorghum bagasse surface appeared cracks, ravines and small holes. The pretreatment damaged the internal structure of cellulose, increasing the surface area of cellulose. FTIR, XRD, NMR detection show that:the four pretreatment have reduced the grain size, change the natural crystalline cellulose. And the crystalline of cellulose changed from theⅠαandⅠβto the Fibril surface cellulose and amorphous cellulose. Thus, this change reduced the crystallinity and changed the internal structure of cellulose as well as cellulose accessibility, and eventually improved the hydrolysis efficiency.