Purification and characterization of a novel cellulase-free xylanase from Acrophialophora nainiana

Abstract

A β-xylanase (XynIII) of Acrophialophora nainiana was purified to homogeneity from the culture supernatant by ultrafiltration and a combination of ion exchange and gel filtration chromatographic methods. It was optimally active at 55°C and pH 6.5. XynIII had molecular masses of 27.5 and 54 kDa, as estimated by gel filtration and sodium dodecyl sulfate–polyacrylamide gel electrophoresis, respectively. The purified enzyme hydrolyzed preferentially xylan as the substrate. The half-lives of XynIII at 50 and 60°C were 96 and 1 h, respectively. It was activated by L-tryptophan, dithiothreitol, 5,5-dithio-bis(2-nitrobenzoic acid, L-cysteine and β-mercaptoethanol and strongly inhibited by N-bromosuccinimide. The presence of carbohydrate was detected in the pure XynIII.