Production, Purification and Comparison of Polygalacturonase from Aspergillus flavus, Aspergillus niger and Penicillium expansum

The research investigated the production, purification and comparison of polygalacturonase (PG) from cassava peels degrading fungi (Aspergillus flavus, Aspergillus niger and Penicillium expansum) isolated from biodegrading cassava peels. The fungi were isolated using cassava peel agar medium and the PG was produced using the solid state fermentation process. The PG was assayed using the modified dinitrosalicyclic acid reagent method and purified by using Sephadex G-100 and Sephadex C-50. The PG were characterized by examining the effect of temperature, stability at 70 ºC, pH, substrate concentration, metal ions and EDTA. The results show that the specific activity of PG were 6.228, 6.444 and 4.569 units/mg protein for A. flavus, A. niger and P. expansum respectively while the purification fold were 75.037, 75.812 and 78.776 for the same organisms respectively. The optimum temperature and pH (45 ºC and 4.5) were the same. It was observed that the PG lost complete activity when heated at 70 ºC for 20 min. Also, the PG activity increased with increase in substrate concentration and increase in metal ions concentration (Na+ , Mg2+, Ca2+ and K+ ). However, the activity of the PG decreased with increase in heavy metal ion concentrations (Hg2+ and Pb2+) and EDTA.