IMPROVED SUBMERGED ASPERGILLUS FICUUM PHYTASE PRODUCTION IN BENCH-TOP BIOREACTORS BY OPTIMIZATION OF FERMENTATION MEDIUM

Phytase is an important feed and food additive, which is used in diets to increase the absorption of divalent ions, amino acids, and proteins in the bodies and to decrease the excessive phosphorus release in the manure to prevent negative effects on the environment. To date, phytase has been mostly produced in solid state fermentations with insignificant production volumes. Thus, there is a need to produce phytase in submerged fermentations, which can be scaled-up for commercial productions. Additionally, optimization of fermentation medium has not been studied well in the literature. Therefore, this study has been undertaken to improve Aspergillus ficuum phytase production in submerged fermentations by optimizing important nutrients in the fermentation medium (glucose, Na-phytate, and CaSO4) using Box-Behnken design of Response Surface Methodology. Also, effects of pH and temperature on phytase activity were studied. Optimum glucose, Na-phytate, and CaSO4 concentrations were determined as 126, 14, and 1.1 g l(-1), respectively. Additionally, pH 5.5 and 55 degrees C were determined as optimum for the produced A. ficuum phytase activity. Under these conditions, phytase activity was increased to 3.45 U ml(-1), which is about 50% higher than the previous results. Furthermore, the lowest activity loss was observed under 4 degrees C storage conditions during 1 week of storage.