ENZYME SACCHARIFICATION OF LOW LIGNIN TRANSGENIC COTTONWOOD BY DIFFERENT PRETREATMENT METHODS

摘要

Low lignin transgenic cottonwood (P. trichocarpa) wood was used to elucidate the effect of four different pretreatment methods on enzymatic saccharification. The lignin contents of three transgenic samples (4CL1-1, 4CL1-4 and CH8-1-4) were 19.3%, 16.7% and 15.0%, respectively, as compared with the wild type (21.3%). The four pretreatments were dilute acid (0.1% sulfuric acid, 185°C, 30 min.), green liquor (6% total titratable alkali, 25% sulfidity based on TTA, 185°C and 30 min.), autohydrolysis (185°C, 30 min.) and ozone delignification (25°C. 30 mim.) Following the pretreatment, enzymatic saccharification was carried out using an enzyme charge of 5 FPU/g of substrates. The removal of lignin and hemicellulose varies with the types of pretreatments and with the lignin content of the transgenic trees. Green liquor removed the most amount of lignin from the substrates, followed by acid, ozone and auto-hydrolysis in that order. The results indicated that lignin content is the main factor affecting the enzymatic hydrolysis. At a given lignin content, pretreatment with ozone delignification had lower saccharification efficiency than the other pretreatment methods.