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

Abstract

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 K _m and k _cat 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.