Purification, characterization and retting of Crotolaria juncea fibres by an alkaline pectin lyase from Fusarium oxysporum MTCC 1755

Using solid-state fermentation, production of an industrially important pectin lyase from a fungal strain Fusarium oxysporum MTCC 1755 was attempted, which was further subjected to purification and characterization. The enzyme was purified by three steps, namely ammonium sulfate fractionation, cation-exchange chromatography on CM cellulose followed by gel filtration chromatography using Sephadex G-100 column. A 16-fold purification with 31.2% yield and 3.2 U/mg specific activity was achieved. The optimum pH of the purified enzyme was 9.0 and stability ranged from pH 5.0–7.0 for 24 h. Optimum temperature of purified enzyme was found to be 40 °C while temperature stability ranged from 10 to 50 °C for 30 min. The Km and kcat of the enzyme was 1.75 mg/ml and 83.3 s−1, respectively. The purified enzyme was found to be highly stimulated by Ca2+ ions while sugars like mannitol and sorbitol, and salts like NaCl and CaCl2 enhanced the thermostability. The purified pectin lyase was found suitable for retting of Crotolaria juncea fiber.