A novel cellulase free alkaliphilic xylanase from alkali tolerant Penicillium citrinum:: production, purification and characterization

Aims: The enzymatic hydrolysis of xylan has potential economic and environment-friendly applications. Therefore, attention is focused here on the discovery of new extremophilic xylanase in order to meet the requirements of industry. Methods and Results: An extracellular xylanase was purified from the culture filtrate of P. citrinum grown on wheat bran bed in solid substrate fermentation. Single step purification was achieved using hydrophobic interaction chromatography. The purified enzyme showed a single band on SDS-PAGE with an apparent molecular weight of c. 25 kDa and pI of 3.6. Stimulation of the activity by beta mercaptoethanol, dithiotheritol (DTT) and cysteine was observed. Moderately thermostable xylanase showed optimum activity at 50 degrees C at pH 8.5. Conclusions: Xylanase purified from P. citrinum was alkaliphilic and moderately thermostable in nature. Significance and Impact of the Study: The present work reports for the first time the purification and characterization of a novel endoglucanase free alkaliphilic xylanase from the alkali tolerant fungus Penicillium citrinum. The alkaliphilicity and moderate thermostability of this xylanase may have potential implications in paper and pulp industries.