Seven cultures of Aspergillus niger from local and international sources were screened for their abilities to produce extracellular polygalacturonase (PG) enzyme using two different assay methods, namely, quantitative viscosity reduction (Reyes units) and liberation of reducing moieties (as galacturonic acid) of standard apple pectin solutions. Appreciable levels of extracellular PG were formed by all tested cultures on wheat bran media as sole nutrients source between 1%-10% (w/v) in tap water with the highest enzyme levels obtained at 5%-10% (w/v) final concentrations. Based upon relative thermal stability and high productivity of PG enzyme the culture Aspergillus niger F-19 was selected for further studies. The selected culture Aspergillus niger F-19 could form PG enzyme on Dox medium supplemented with pectin, wheat bran, orange or lemon peels with the highest enzyme level formed on 5% wheat bran medium supplemented with 4% orange peels and 0.2% ammonium sulfate. The maximum specific enzyme activity and enzyme yield in the culture supernatant were attained after 4-6 days of incubation at 30°C with notable stability in the culture fluid at least up to nine days incubation period. Application studies were carried out on the possible use of the enzyme in orange juice production. Optimum enzyme concentration for juice production was 10.4 mg protein/150 gm of fruits using 30 minutes maceration reaction time at 50°C. Under optimized reaction conditions more than 25% increase in total juice yield could be obtained with excellent chemical, physical and organoleptic properties as compared to those of the control juice (without enzyme treatment). The obtained results were discussed in the light of possible application in orange juice industry in Egypt.