Enhanced submerged phytase fermentation with Aspergillus ficuum by optimization of process conditions for batch and fed-batch fermentations

Phytase breaks down phytate, which causes malnutrition by binding divalent ions, amino acids, and proteins in animals. Additionally, phytate causes excessive phosphorus accumulation in the manure, which has negative effects on the environment such as changing flora and fauna. In order to prevent these negative effect of phytate, phytase enzyme must be produced efficiently. However, the current solid-state productions of phytase cannot meet the demand. Therefore, this study aimed to increase the phytase activity in submerged fermentations by selection the best microbial strain, optimizing process conditions such as temperature, pH, and aeration as well as medium composition such as glucose, phytate, and CaSO₄ and performing batch and fed-batch fermentations. As a result, Aspergillus ficuum (NRRL 3135) was selected as the most productive strain among four evaluated. In batch fermentations optimum temperature, pH, and aeration were determined as 33^oC, 4.5, and 0.9 vvm, respectively. Phytase activity was measured as 2.27 U/ml under these conditions, which was 2-fold higher compared to shake-flask fermentation results. Also, optimum glucose, phytate, and CaSO₄ concentration in the fermentation medium were determined as 126 g/L, 14 g/L, and 1.1 g/L, respectively and phytase activity increased to 3.45 U/ml under these conditions. Furthermore, fed-batch studies showed that 60 g/L of glucose and 10 g/L phytate addition at 96^th hour of fermentation enhanced activity to 3.87 U/ml and 4.82 U/ml, respectively. This study clearly showed that this is an enhancement of phytase toward commercial production.