14-16: Isolation, purification and characterization of thermophilic alkali – stable endoxyloglucanase from Aspergillus terreus

The production of hemicellulases for bioprocessing agricultural wastes is proving to be cost effective and environmentally viable. There is a growing demand for specific, efficient and cheap hemicellulase for use in the production of oligosaccharides and monosaccharides for its use as nutraceuticals and saccharification in the production of ethanol, respectively. A thermophilic alkali – stable endoxyloglucanase is isolated from the culture filtrate of Aspergillus terreus by submerged fermentation. The enzyme is purified to homogeneity with an yield of 12.5% and 84 – fold purification by chromatographic techniques using CM – Sepharose and Sephadex G – 100. Electrophoresis showed a single xyloglucanolytic activity and protein band. The enzyme is a monomer having a molecular weight of 75.8 kD as determined by SDS – PAGE and HPLC using TSK gel 3000 swxl column. The enzyme exhibited high activity only against tamarind xyloglucan (amyloid, Megazyme, Ireland) and did not act on starch, oat spelt xylan, chitin, laminarin, avicel, carboxymethylcellulose (CMC), pectin, p – nitrophenyl – β – D –glucoside and p – nitrophenyl – β – D – galactoside. The viscosity of the tamarind xyloglucan solution is reduced by 85% within 10 mins of the addition of the enzyme and is characterized as an endoxyloglucanase. The enzyme had a K_m of the 116 mg%, optimum pH and temperature of 5.0 and 60°C and stable between pH 7 to 11 and 20°C to 90°C, respectively. The enzyme was activated by MnSO₄, MgSO₄, CoCl₂ and ZnCl₂ and completely inhibited by HgCl₂ and EDTA.  

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