EFFECT OF SULFITE PRETREATMENT TO OVERCOME THE RECALCITRANCE OF LIGNIN (SPORL) ON ENZYMATIC SACCHARIFICATION OF CORN STALK

In order to maximize the glucose yield in the subsequent enzymatic hydrolysis, corn stalk was pretreated with sulfite to overcome the recalcitrance of lignocellulose (SPORL) under different operational conditions (pretreatment temperature, bisulfite charge, and pH). The parameters optimized included sodium bisulfite charge from 0 to 7% (w/w) on od dry (od) substrate, pretreatment temperature 160 to 190 degrees C, and pH 2.2 to 6.7 required in the process. The results indicated that after the SPORL pretreatment of corn stalk with 7% bisulfite at 180 degrees C for 30 min, about 69% and 62% of enzymatic conversion efficiency and glucose yield were achieved, respectively, with emzyme loading of about 5 FPU cellulase per gram of cellulose plus beta-glucosidase after 72 h hydrolysis. Temperature had a positive effect on enzymatic hydrolysis. The enzymatic conversion efficiency was reached 81.04% with 7% sodium bisulfite at 190 degrees C for 30 min. The pH of pretreatment liquor plays a crucial role in enhancing enzymatic digestibility of SPORL substrate.