Seventy five fungal cultures were isolated from decayed citrus fruits and tested for their pecti-nolytic activity. Thirty six out of them proved to have ability for pectinase enzymes production. These isolates were identified and classified into twenty strains belonging to eleven species ap-pertaining to six genera of fungi. Aspergillus was the first pre-dominant genus followed by the genera of Cladosporium and Penicillium.
Evaluation of the twenty strains for their ability to produce pectinase enzymes indicated that the greatest clearing zones among the locally isolated fungi were observed with Aspergillus niger AUMC 4156 (22 mm) and Paecilomyces variotii AUMC 4149 (21 mm), which was mostly comparable with the pectinolytic activity of the imported strain Aspergillus niger NRRL 337 (23 mm). Studying the environmental and nutritional factors leading to maximum pectinase (s) produc-tion by these three strains showed that, the optimum incubation temperature and period for pecti-nase (s) production by Aspergil-lus niger NRRL 337, Aspergillus niger AUMC 4156 and Paecilo-myces variotii AUMC 4149 were 30˚C and 5days, respectively. The optimum pH values were 5 – 6, 5 and 6 for A. niger NRRL 337, A. niger AUMC 4156 and Paecilomyces variotii AUMC 4149, respectively. The best in-oculum size was 1% for Asper-gillus niger NRRL 337, and 2% for both Aspergillus niger AUMC 4156 and Paecilomyces variotii AUMC 4149. Pectin at concentration of 2% proved to be the best carbon source followed by starch for all the studied fun-gal strains. Also, it was found that, the maximum enzyme pro-duction was attained by using of 2% yeast extract as the sole ni-trogen source for all the studied fungi.