Abstract

We reported the partial purification and characterization of polygalacturonases from fruit spoilage Fusarium oxysporum and Aspergillus tubingensis isolated from banana and peach, respectively. By using diethylaminoethyl (DEAE)-Sepharose column, one and two forms of polygalacturonases were separated from F. oxysporum (PGase) and A. tubingensis (PGaseI and PGaseII), respectively. The polygalacturonases examined had higher affinity toward various polygalacturonic acids and pectins. The apparent K_m and V_max values were reported for the enzymes. Acidic pH optima (4.0 to 6.0) was also reported for the enzymes. Optimal temperature and thermal stability of the enzymes showed a range from 40 to 60°C. The effect of metal cations on the enzymes was studied. The most chemical compounds caused moderate inhibitory effect except benzoic and citric acids which had strong inhibitory effect on the polygalacturonases. The benzoic and citric acids were used as antifungal compounds for F. oxysporum and A. tubingensis. The citric acid was found to be more effective against fungal growth than benzoic acid.

Key words: Fruit, spoilage, Fusarium oxysporum, Aspergillus tubingensis, polygalacturonase.