Mutagenesis Strategies for the Enhancement of Glucose Oxidase Production from Corn Steep Liquor

During screening of the twenty eight Aspergillus and Penicillium species for GOD production, only A. niger (84) was observed to release high extra (3.15 U ml-1) and intracellular (9.30 U mg-l) GOD activity. Conidia of A. niger S4 were subjected to mutagenesis with UV radiation, nitrous acid, and sodium azide, as a single or combined treatments, and GOD activity was detected with the diffusion plate method. Out of 27 over producing mutants tested in shaken flasks, UVNA54 mutant strain showed the highest level of GOD activity (171 %, higher than the wild type). Using CSL at concentration 25 ml rl as the sol nutrient source, the enzyme activity was increased to 5.16 U ml-1 and 22.40 U mg-1 for extra and intracellular, respectively. Viable cell numbers of Pseudomonas and Salmonella spp. decreased as the concentration of the produced enzyme increased from 1 to 3 U ml-1