Purification and characterization of an alkaliphilic endo‐xylanase from Streptomyces althioticus LMZM and utilization in the pulp paper industry

BACKGROUND: Xylanase is the key enzyme involved in the conversion of lignocelluloses. RESULTS: An extracellular xylanase from Streptomyces althioticus LMZM submerged culture medium using corncob was purified and characterized. The enzyme was purified 12.65‐fold through ammonium sulphate precipitation, Sephadex G‐25, DEAE cellulose chromatography, followed by gel filtration through a Sephadex G–100 column. The molecular mass of purified xylanase was about 31.75 kDa. The enzyme was an endo‐xylanase, as it degraded xylan to xylooligosaccharide with non‐xylose after 24 h. The purified enzyme showed optimum activity at 60 °C and at pH 8.0 but remained active over a wide range of pH (6.0–11.0) and temperature (40–80 °C). The enzyme retained 98.72% and 69.50% residual enzyme activity at pH 8.0 and at 60 °C after 1 h. The Kₘ and Vₘₐₓ values were found to be 43.03 mg mL⁻¹ and 312.5 µmol (min mg⁻¹), respectively. The enzyme was remarkably activated by cysteine and Cu²⁺, and its activity was strongly inhibited by Hg²⁺. The brightness of kraft pulp was improved by this xylanase. CONCLUSION: Since the enzyme was active over a wide range of pH, and remained active at high temperature, it could find potential uses in biobleaching processes in pulp paper industries and in the production of xylooligosacaharides. © 2015 Society of Chemical Industry