EFFECT OF ALKALINE EXTRUSION PRETREATMENT OF WHEAT STRAW ON FILTRATE COMPOSITION AND ENZYMATIC HYDROLYSIS

摘要

Thermo-mechano-chemical pretreatment of wheat straw with NaOH concentrations ranging from 1% to 6% w/w in a single screw extruder was investigated in terms of filtrate composition and sugar yields after enzymatic hydrolysis. The filtrates contained lignin, xylose and its oligomers, glucose, arabinose, acetic and formic acid. The yields of all the substances increased with rising NaOH concentration. After extrusion of the wheat straw with 6% NaOH, 53% of lignin, 34% of arabinan, 9% of xylan and 2% of glucan were transferred into the filtrate Alkaline extruded wheat straw was subsequently extracted at 80 degrees C for 30, 60, 120 and 180 minutes in order to increase the efficiency of enzymatic hydrolysis. After extracting the alkaline extruded wheat straw for 180 minutes, 70% of lignin, 50% of arabinan, 15% of xylan and 3% of glucan were removed. The results of polysaccharides conversion showed that alkaline extrusion pretreatment increased the accessibility of hydrolytic enzymes to the wheat straw structure. With increasing concentration of NaOH, the conversion of glucan increased from 40.5 to 77.0%, that of xylan - from 27.5 to 72.1% and that of total polysaccharides - from 34.8 to 74.6%. The addition of the alkaline extrusion pretreatment only slightly increased the conversion of glucan from 78.5 to 81.2%, that of xylan - from 74.0 to 77.7% and that of total polysaccharides from 75.6 to 79.0%.