Effect of culture media and fermentation parameters on phytase production by the thermophilic fungus Myceliophthora thermophila in solid state fermentation

Phytase production by thermophilic filamentous fungi was evaluated in solid state fermentation. A total of twenty strains belonging to Rhizomucor spp. (9), Myceliophthora thermophila (6), Thermoascus aurantiacus (4), and Paecilomyces variotii (1) were screened. Sugar cane bagasse was used as support for assessing the effect of different carbon and nitrogen sources, as well as mineral salts. Solid state fermentation parameters (initial moisture, initial pH, aeration rate) were also studied. Myceliophthora thermophila showed higher phytase activity and was selected for further studies. Synthetic culture media containing different carbon and nitrogen sources were tested for phytase production by this species in solid state fermentation. M. thermophila showed the highest phytase activity after 36 h of fermentation, when grown on a synthetic culture medium (glucose 10 g/L; phytic acid 2 g/L). (NH4)2HPO4, CaCl2, and MgSO4 favored high phytase activity in M. thermophila. Optimal initial culture conditions for phytase production were determined (pH, 6.0; moisture, 75%; aeration rate, 25 ml/min/column). In comparison with Aspergillus ficuum, the phytase activity of M. thermophila was 2.5 times higher. Phytase was most active at pH 5.5 and 45-50 C, but it was also active at 70 C. Optimization studies resulted in a 4-fold increase of phytase activity.