Isolation of an Arginase-Producing Aspergillus niger AUMC16187 from Sandy Soil at Al-Gharbia Governorate, Egypt and Characterization of the Produced Enzyme

This study aimed to isolate arginase-producing fungi from 24 soil samples collected from four Egyptian governorates, then to identify the most potent fungal isolate both morphologically and genetically via detecting ITS regions of 18S rRNA sequence. Optimal conditions for enzyme production and activity including incubation or reaction time, temperature, pH, carbon and nitrogen sources, additional elements, different amino acids, and EDTA were also investigated. Arginase was purified from concentrated clear culture filtrate with gel filtration using Sephadex G-50 column. Aspergillus niger AUMC16187 was identified as the most efficient arginase-producer among 68 fungal isolates isolated from 24 soil samples and screened for arginase production. Maximum arginase production was achieved at 7th day of incubation, 27°C, and pH 7, using 1% dextrose and 2% ammonium chloride as carbon and nitrogen sources, respectively, 0.2% magnesium chloride as additional element, and 0.15% glutamine. SDS-PAGE analysis of purified arginase showed two bands at molecular weights of approximately 127 and 70 kDa. Purified arginase displayed maximum activity at 40°C, pH 7, after reaction time of 10 and 15 min, and was most stable at 30-50°C. All EDTA concentrations completely inhibited enzyme activity revealing that it is a metalloenzyme. The enzyme demonstrated significant cytotoxic effects against human melanoma cells (A431), indicating its potential as an anticancer agent.