Purification and Characterization of Pectinase from Aspergillus niger Produced via Submerged Fermentation Using Wheat Bran

Abstract

This study involved the isolation, screening, and identification of a pectinase-producing fungus from soil collected at a vegetable waste dump site. The isolated fungal strain was subsequently cultivated under optimized conditions to produce pectinase, which was then purified and subjected to biochemical characterization. The fungus was initially isolated on pectinase screening agar medium containing 1% pectin, where the formation of a clear zone indicated pectinolytic activity. Morphological and molecular analyses identified the strain as Aspergillus niger. Enzyme production was carried out using submerged fermentation (SmF). Purification of the exopectinase was achieved through a combination of ammonium sulphate precipitation, dialysis, and chromatographic techniques, including gel filtration. Among the different ammonium sulfate saturation ranges (0–20%, 20–40%, 40–60%, 60–80%, and 80–100%), the 70–80% fraction showed the highest enzyme activity. This fraction exhibited maximum protein content, total exopectinase activity, specific activity, purification fold, and recovery percentage. The molecular weight of the purified enzyme was subsequently determined using SDS-PAGE. The Sephadex G-100 purified samples revealed a distinct band with molecular weight of 60 kDa. Studies on characterization of purified enzyme revealed that the A. niger showed good production of exopectinase. Studies on the characterization of the purified enzyme revealed that A. niger showed efficient exopectinase production. In the present investigation, exopectinase activity from A. niger was stable and showed maximum activity at pH 6.0 (0.076U/mL). The enzyme exhibited higher activity at an optimum temperature of 40°C (0.685U/mL) and retained approximately (57.4%) of its activity after 30 minutes of incubation, indicating good thermal stability. Among all the metal ions tested, KCl enhanced enzyme activity by (18.15%) whereas FeCl3 exhibited a maximum inhibition of 76.93% and CoCl2 showed complete inhibition of enzyme activity.