Screening and Optimization of Process Parameters for the Production of l -asparaginase by Indigenous Fungal-Type Strains

Microbial l -asparaginases have received significant attention due to their potential for applications in cancer treatment and for preparation of acrylamide-free baked and fried food. Eleven fungal-type strains were obtained from Iranian Biological Resource and screened for production of l -asparaginase using dye-based plate assay on modified Czapek Dox medium. The efficiency of three different dye indicators including phenol red, bromothymol blue and cresol red was evaluated. Production mode was also evaluated by the agar well diffusion method. A comparative study was carried out to evaluate l -asparaginase production in submerged condition by enzymatic assay using Nessler’s reagent. Optimization of the enzyme production by the selected superior strain was performed using one factor at a time method for temperature, inoculum and different carbon and nitrogen sources. Five-type strains showed positive l -asparaginase activity in preliminary screening. Phenol red and bromothymol blue showed better differentiable zone of hydrolysis and consistent results in comparison with cresol red. The results also indicated that l -asparaginase production mode is extracellular. l -asparaginase production by Fereydounia khargensis IBRC-M 30116 T which showed the highest zone of color change was then optimized. The optimum enzyme activity of 61.3 U. mL −1 was obtained with 9% inoculum, at a temperature of 30 °C and at the presence of ammonium chloride as nitrogen source and with glycerol as the carbon sources. The study revealed that, apart from bacteria, yeast and yeast-like microorganisms could be considered as novel and appropriate sources for production of the high yield of l -asparaginase.