Two distinct experiments were conducted simultaneously with phytases of Aspergillus oryzae and A. niger for determining enzyme activity in response to storage period (up to 180 days at room temperature - RT). In the first experiment, enzymes were stored as they were acquired (pure form) and the activity was measured periodically during 180 days of storage at RT. In the second experiment, the phytases were incorporated to a supplement containing vitamins, minerals, and amino acids; and then this supplement was stored at RT up to 180 days, so that every 30 days of storage was collected one aliquot from each replicate for determining enzymatic activity. In conclusion, the phytase activity is affected by storage duration. To ensure 80% of the initial activity, the phytases of A. oryzae and A. niger can be stored in the pure forms for up to 53 and 135 days at RT, respectively. However, if the phytases of A. oryzae and A. niger are incorporated to a supplement containing vitamins, minerals, and amino acids then the storage period at RT should not exceed 67 and 77 days, respectively.
Aspergillus niger; Aspergillus oryzae; enzyme; phytate; phytic acid
