PURIFICATION AND PARTIAL CHARACTERIZATION OF AN ENDO-POLYGALACTURONASE FROM ASPERGILLUS NIGER

Abstract

A pectinase was identified and isolated from a commercial Aspergillus niger pectinase preparation. The crude enzyme preparation, which was prepared by precipitation of the water extract of the culture of A. niger with ammonium sulfate, was further fractionated by three steps of chromatography, i. e., cation exchange, hydrophobic interaction and anion exchange, to obtain an electrophoretically homogeneous pectinase. The molecular weight of the purified enzyme was estimated by SDS-PAGE to be about 40.4 kDa under both nonreducing and reducing conditions, with the optimum pH at 5.0 and the optimum temperature at 36C. The enzyme was stable at temperatures below 35C. The partial N-terminal amino acid sequence data analysis of the first 19 amino acids of the obtained pectinase revealed 94.7% and 89.5% homology with two reported pectinases from A. niger. L'objectif de cette etude est d'isoler et de caracteriser les enzymes pectolytiques de la preparation de pectinase commerciale la plus extensivement utilisee en Chine. Le poids moleculaire de l'enzyme purifiee est estime a environ 40kDa, avec un pH optimum a 5,0 et une temperature optimale de 36°C. L'enzyme est stable a des temperatures inferieures a 35°C.