tailieunhanh - Purification and characterization of endoxylanase Xln-2 from Aspergillus niger B03

An extracellular multiple form of endoxylanase was isolated from the xylanolytic complex of Aspergillus niger B03. The enzyme was purified to a homogenous form using ultrafiltration, anion exchange chromatography, and gel filtration. | G. DOBREV, B. ZHEKOVA Turk J Biol 36 (2012) 7-13 © TÜBİTAK doi: Purification and characterization of endoxylanase Xln-2 from Aspergillus niger B03 Georgi DOBREV, Boriana ZHEKOVA Department of Biochemistry and Molecular Biology, University of Food Technologies, 4002 Plovdiv - BULGARIA Received: Abstract: An extracellular multiple form of endoxylanase was isolated from the xylanolytic complex of Aspergillus niger B03. The enzyme was purified to a homogenous form using ultrafiltration, anion exchange chromatography, and gel filtration. It was a nonglycosylated protein with a molecular weight of 20,000 Da as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and 21,000 Da as determined by gel filtration. The optimal pH for the enzyme action was and the optimal temperature was 55 °C. Endoxylanase stability was significantly improved in the presence of glycerol and sorbitol. The enzyme activity was activated by Mn2+ and Co2+, and it was inhibited by Ag+, Cu2+, Fe3+, Fe2+, and Pb2+. The substrate specificity and the product profile of the enzyme suggested that it was an endoxylanase. The enzyme showed a synergism with another endoxylanase from Aspergillus niger B03 in xylan hydrolysis. Key words: Endoxylanase, purification, characterization, Aspergillus niger, xylan Introduction Lignocellulose is the most abundant renewable biomass available on our planet. It comprises 3 major groups: cellulose, hemicellulose, and lignin (1). Xylan, the principal component of hemicellulose, is formed by a backbone of β-1,4-linked-D-xylopyranosyl residues, with different substitute groups in the side chain. Complete degradation of these polysaccharides requires an enzymatic complex including xylanases (1,4-β-D-xylan xylanohydrolase, EC ) and β-xylosidases (1,4-β-D-xylan xylohydrolase, EC ). These enzymes are responsible for the hydrolysis of the main chain. Enzymes such as α-L-arabinofuranosidase (EC ), .