Tuesday, April 20, 2010

Application of immobilized xylanase on hydrolysis of soluble wood hemicelluloses after using microwave and organosolv pre-treatments

Anny Manrich1, Doris Schieder2, Raquel Lima Camargo Giordano1, and Martin Faulstich2. (1) Chemical Engineering Department, Universidade Federal de S„o Carlos, Washington Luiz, Km 235, Monjolinho, S„o Carlos, SP, Brazil, (2) Straubing Center of Sciences, Technische Universitšt MŁnchen, Schulgasse 16, Straubing, Germany

The influence of two pre-treatments, microwave-water and the organosolv-ethanol, on the enzymatic hydrolysis of oligosaccharides originated from pre-treated wood sawdust was investigated. The performances of xylanase free and immobilized on glyoxyl agarose were compared. The pre-treatment process aimed at to overcome the recalcitrance of the lignocelluloses material, dissolving the hemicelluloses, but preserving xylan in the form of oligosaccharides. Pre-treat wood particles had 2mm size. Microwave temperatures between 100°C and 150°C and treatment times between 10 and 60 minutes were investigated. Organosolv pre-treatment using a 1:1 ethanol: water solution was performed in a reaction autoclave during 60 minutes at 180°C. Sawdust from beech wood (hardwood) and poplar (softwood) were used. Sugar contents from both woody material and soluble lignocelluloses were analyzed using sulfuric acid hydrolysis followed by HPLC analysis. Hydrolysis was performed in shaker at 60°C and samples were analyzed after 24, 48 and 72 hours by measuring the amount of the reducing sugars. The clogging of the support pores by the substrate, soluble hemicelluloses containing lignin, after hydrolyses of microwave pre-treated sawdust may could explain the loss of activity observed for the immobilized enzyme. This hypothesis is corroborated by the good results obtained after the organosolv pre-treatment of the beech wood sawdust, which dissolved lignin as well as 50% of the pentosan sugars, without generating great amount of co-products. Using this latter substrate, more than 70% of the xylan in form of soluble oligosaccharides could be successfully hydrolyzed by both free and immobilized xylanase, indicating that the organosolv pre-treatment is a good alternative to obtain oligosaccharides and monosaccharide derived from xylan.