EFFECTS OF REMOVAL OF HEM1-CELLULOSES AND LIGNIN DURING SPORL PRETREATMENT ON ENZYMATIC SACCHARIFICATION FROM ASPEN CHIPS

摘要

Sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL) was applied to aspen chips to enhance the efficiency of enzymatic saccharification of cellulose. It is well known that hemicelluloses and lignin are inhibitors to enzymes. Aspen wood chips were pretreated with sulfur acid (0~5.5%, on oven dry wood, the same in the following) and sodium bisulfite (0~4.5%) at 160 to 180 °C for 0 to 30 min, and then refined using a disk refiner with 0.76 mm disk plate gap and 10% refining discharge consistency to produce lignocellulosic substrates. SPORL removed most of hemicelluloses and some lignin, which resulted in high enzymatic saccharification of pretreated solid substrate. The resultant substrates were enzymatically saccharified using 7.5 FPU cellulase plus 11.25 IU P-glucosidase per gram of od substrate. As expected, more hemicelluloses were removed from aspen chips at increased sulfuric acid charge. Most of the removed hemicellulsose were converted to monomeric sugars with highest yield of approximately 90% theoretical. The substrate cellulose enzymatic digestibility (SED) of aspen substrate is proportional to removal of xylan from aspen chips. It was also found that more than 30% of lignin can be removed from aspen chips by SPORL pretreatment with sodium bisulfite charge of 3.0%. Effeciency of enzymatic saccharification of substrate, pretreated with 1.1% sulfuric acid and 3.0% sodium bisulfite, was more than 95%, of the theoretical value. Comparisons between dilute acid and SPORL will be made in terms sugar and ethanol yield.