Effect of gamma irradiation on the production of cell wall degrading enzymes by Aspergillus niger

Fungi occurring in Egyptian fruits in the City of Qena were studied. Results from the examination of 25 replicated samples of plums, pears and apples are reported. Examinations were carried out by direct plating after surface disinfection in a 0.5% (w/v) calcium hypochlorite solution on Czapek's-Dox agar. The dominant fungus found in the three types of fruit was Aspergillus niger, which was present in 88% of plum samples, 80% of pear samples and all of the apple samples. The lowest dose of gamma irradiation (1 MCi for 10 min) enhanced the three isolates of A. niger investigated to produce more biomass and polygalactronase, pectinmethylglacturonase, cellulase and protease. The higher doses (1 MCi for 20 and 30 min) were inhibitory to the growth of A. niger.