Cellulase Hydrolysis Of Sodium Hydroxide Pretreated Corn Straw

Anaerobic digestion of straw is blocked by the dense structure of lignocellulose. Effective pretreatment is needed to improve the biodegradable performance of the straw. Hydrolysis stage is the rate-limiting step of anaerobic digestion process. The use of enzyme can speed up the hydrolysis process in order to shorten anaerobic digestion time.Corn straw was pretreated by NaOH under different concentration and pretreatment time. The weight lose, lignocellulose reduction, concentration of COD and reducing sugar from the soaking liquid of the pretreated straw and the microstructure change were determined. The results showed that the test group with NaOH concentration of10%and pretreatment time of ld reached the highest performance. The lignocellulose and hemicellulose reduction reached32.19%å'Œ50.00%respectively; Concentration of COD reached62.5g·L-1; Microstructure change showed surface of the corn straw was broken. Hemicellulose characteristic peak disappeared through the pretreatment, but the crystal structure of the cellulose was still unchanged.Cellulase hydrolysis test was carried out with corn straw which was pretreated after different conditions. The reducing sugar concentration, cellulose and hemicellulose reduction, hydrolysis rate and the microstructure change were determined. Experimental results showed that the test group with NaOH concentration of10%and pretreatment time of1d reached the highest performance. The reducing sugar concentration of the cellulase hydrolysis was46.70g-L-1; Cellulose and hemicellulose degradation rate was50.87%å'Œ80.54%respectively and the hydrolysis rate was51.07%. Microstructure showed that the inside of the straw was exposed. The crystallinity of cellulose increased because a large number of amorphous cellulose was hydrolyzed.Single factor and orthogonal experiments of cellulase hydrolysis was carried out with corn straw which was pretreated with NaOH concentration of10%and pretreatment time of1d. The result showed that the optimal levels of factors were as follow:temperature of40℃, pH=5, the cellulase concentration of300U-g-1(TS), reaction time of48h. The reducing sugar concentration reached51.00g-L-1under the optimal conditions. Analysis of variance showed that pH effected the reducing sugar concentration significantly. The prior order of factors ranged as follow:pH> cellulase concentration>temperature.