Purification and characterization of an alkaline xylanase from Streptomyces viridosporus T7A

Abstract

Streptomyces viridosporus T7A produces a large amount of extracellular xylanase activity. We have isolated and purified an alkaline xylanase from culture supernatants of this organism. Purification was achieved by treatment of the culture supernatant with Q-Sepharose, concentration of the unbound proteins by ultrafiltration, fractionation of these proteins by Sephadex G-75 gel filtration chromatography, followed by Rotofor preparative isoelectric focusing. The xylanase has a molecular mass of 59 kDa as determined by capillary electrophoresis. The purified xylanase has a pI of 10.2–10.5, a pH optimum of 7.0–8.0, and a temperature optimum of 65–70°C. The xylanase is strongly inhibited by Hg 2+, Cu 2+, and Fe 3+ metal ions. The purified protein shows activity on birchwood and oat spelt xylans, but does not exhibit activity toward galactomannan, arabinogalactan, lichenan, or carboxymethylcellulose. This enzyme could have potential uses in biotechnology applications due to its high pH and temperature optima and unique substrate specificity.