Purification and biochemical characterization of pectinase produced by Aspergillus fumigatus isolated from soil of decomposing plant materials

Abstract

This study isolated, screened, and identified a pectinase-producing fungus from a decomposing plant material. It also cultured the isolated fungus under optimized conditions to obtain crude pectinase enzyme as well as purified and investigated the biochemical characteristics of the purified enzyme. The fungal strain was isolated on pectinase screening agar medium containing 1% pectin and obtained a clear zone. It was identified as Aspergillus fumigatus and cultivated for enzyme production using banana, plantain, and orange peels as the solid substrate. Under optimized conditions, a maximum of 3.52 U/ml pectinase activity was obtained at 65% moisture content after 144 h (6 days) of incubation period on orange peel, 1.5 ml inoculum, and 3% salt content. A. fumigatus pectinase was purified 4.45-fold and a yield of 26.16% with a specific activity of 38.88 U/mg. The molecular weight determined on sodium dodecyl sulfate (SDS-PAGE) was 31.6 kDa. The pectinase exhibited maximum activity at 60°C, optimum pH of 5.0, and stability at 40–50°C. The enzyme showed a preference for polygalacturonic acid as its primary substrate with a KM 3.08 mg/ml and Vmax of 1.61 U/ml. The enzyme was activated by 0.5 mM Na+, K+, and 1–5% toluene. The enzyme activity was inhibited by metal cations; 20% ethanol, 4.0 mM SDS, and L-cysteine. The obtained results showed that A. fumigatus pectinase could be a candidate for potential industrial and biotechnological application.