Semi-quantitative detection for L-asparaginase producing fungi and the impact of carbon and nitrogen sources on enzyme activity

ObjectiveTo semi-quantitively screen filamentous fungi isolated from different habitats for L-asparaginase production by three indicators; phenol red, cresol red and bromothymol blue and to examine the impact of different carbon and nitrogen sources on the enzyme production using different fungal isolates. Materials and methodsFifty-five fungal isolates were tested for L-asparaginase production by plate assay using Modified Czapek-Dox (MCD) medium. The enzyme activity was estimated using the Nessler method which measures the concentration of ammonia formed owing to the enzyme action on the substrate. The impact of nitrogen and carbon sources on the enzyme production was done by using the best three L-asparaginase producers from the semi-quantitative screening. Results and conclusionsA total of 53/55 (96.36%) fungal isolates were L-asparaginase producing strains, of them, Cladosporium tenuissimum, Penicillium camembertii and Aspergillus carneus showed high enzyme production. Production of L-asparaginase was higher with the glucose and urea as carbon and nitrogen sources, respectively. The highest enzyme level (5,558 U/ml) was produced by C. tenuissimum in a glucose-containing medium. This study shows that P. camemberti, A. carneus, and C. tenuissimum are good L-asparaginase producers and thus could be used for L-asparaginase production