Purification and characterization of an alkaline pectin lyase from Aspergillus flavus

An alkaline pectin lyase secreted by Aspergillus flavus MTCC 7589 was purified to electrophoretic homogeneity using ammonium sulphate fractionation, anion exchange chromatography on DEAE cellulose and gel filtration chromatography on sephadex G-100. The pH and temperature optima of the enzyme were found to be 8.0 and 50 °C. The enzyme was found to be stable for 24 h in the pH range 4.0–10.0. The enzyme does not loose activity up to 50 °C if exposed for 1 h. Addition of ammonium sulphate in the range of 0.1–2.0 M increased the thermostability of the enzyme, 0.6 and 1.8 M of ammonium sulphate providing complete stability at 60 and 70 °C respectively. The values of Km and kcat of the enzyme were 0.59 mg/ml and 52.2 s−1 respectively. The molecular weight was found to be 38 ± 01 kDa. The purified enzyme showed efficacy in retting of Crotalaria juncea fibers.