Production and chromatographic behaviour of polygalacturonase from Pleurotus ostreatus on immobilized metal chelates

Abstract

A strain of Pleurotus ostreatus was grown in submerged culture in tomato pomace as sole carbon source for production of polygalacturonase. The culture of P. ostreatus revealed a peak of polygalacturonase activity (2181 U/l) on 4th day with specific activity of 42.8 U/mg protein. Differential chromatographic behaviour of polygalacturonase, xylanase and laccase from P. ostreatus was investigated on immobilized metal chelates. The effect of ligand concentration, pH, the length of spacer arm and the nature of metal ion was studied for enzyme adsorption on immobilized metal affinity chromatography (IMAC). The presence of imidazole in the equilibration buffer abolished the adsorption of the enzymes to immobilized metal chelates. A one-step purification of polygalacturonase from P. ostreatus was devised by using a column of Sepharose 6B-EPI 30-IDA-Cu(II). Purified enzyme exhibited a specific activity of about 1600 U/mg protein, final recovery of enzyme activity of 80% and a purification factor of about 65. The purified enzyme preparation was analysed by SDS-PAGE as well as by in situ detection of enzyme activity. Purified preparation of polygalacturonase exhibited a pH and temperature optima of activity at 7.0 and at 50 °C, respectively. The kinetic parameters ( V max, K m, K cat and K cat/ K m) of purified enzyme were found to be 5530.8 ± 260.7 U/mg of protein, 13.23 ± 2.79 mg/ml of polygalacturonic acid, 5553.01 ± 261.7 s −1 and 419.72 s −1 mg −1, respectively. Purified enzyme exhibited a half-life (t 1/2) of 60 ± 7.45 min and 35 ± 0.37 min at 50 °C and at pH 6.0 and 7.0, respectively.