Monday, May 2, 2011
Grand Ballroom C-D, 2nd fl (Sheraton Seattle)
Xylooligosaccharides (XOS), small oligomers of xylose (2-5 xylose-units), are valuable products derived from xylan, the main polymer of hemicelluloses. Sugar cane bagasse contains circa 30% of hemicelluloses (w/w). The production of XOS from lignocellulosic material requires extraction of oligomeric xylan, which must be hydrolyzed by endoxylanases under very controlled conditions, in order to produce XOS. Generation of xylose must be avoided, since its separation from XOS is necessary and expensive. Three commercial xylanases (Novozymes 50014 and 22036 and Genencor XY) and a recombinant xylanase from Bacillus subtilis were tested to hydrolyze Birchwood Xylan. In order to extract xylan, sugar cane bagasse was submitted to organosolv pretreatment, using 50% of ethanol (v/v) and solid:liquid ratio of 1:10 (w:v), with degrees of severity (DS) 4.1-5.9, 150-190°C, 30-90 min. For DS 4.1, 30, 50 and 70% ethanol solutions (v/v) were tested. The best result for XOS production was obtained at 170°C, 60 min, 50% ethanol, with 42.3% xylan extraction, 90% as xylooligomers. The best enzyme was the xylanase from Bacillus subtilis, which did not produce xylose, even after 6 hours of hydrolysis. All other xylanases generated small amounts of xylose. Xylotriose was not detected when Genencor XY was the catalyst. The results indicate that kinetic studies with each enzyme are crucial to define optimal operational conditions for this process.