PRODUCTION OF PHYTASE BY ASPERGILLUS TERREUS AND EVALUATING ITS STABILITY

Abstract

Secretory capacity of fungi, Aspergillus terreus (A. terreus), for phytase production is up to the mark. Soil samples containing A. terreus (n=20) were randomly collected in sterile plastic zipper bags, and recognized microscopically and morphologically to screen for phytase production. In the present study, A. terreus phytase production was quantified by providing different physical conditions i.e. temperature and pH to get their optimum level. Thermal stability was obtained by measuring stability at temperature range of 35°C, 55°C, 75°C, and 95°C, whereas, pH stability was estimated at intervals of 2h, 4h, 6h, and 8h. Chemical stability of phytase was judged by analyzing the effects of common earth crust metal ions such as Na+1, K+1, Ba+2, Ca+2, Cu+2, Mg+2, Mn+2, and Fe+3. Phytase production was assessed on phytase screening medium to observe the zone of hydrolysis. The highest phytase production was given by sample 16 (PAST-16) which was; 271.49 ± 8.14 units/mL (FTU/mL) and the lowest was given by sample 3 (PAST-3); 92.15 ± 5.53 FTU/mL. Temperature induced reduction in phytase enzyme and the highest reduction was noted at 95°C for 1 hour and the lowest reduction was recorded at 35°C for 15 min. Moreover, acidic pH (pH=2) induced more reduction for 1 hour exposure than high pH (pH=6) for 15 min. All metal ions, at their high concentration, adversely affected the phytase activity of A. terrus and Cu+2 showed the maximum reduction in phytase. Thus, the present study explored the physico-chemical stability of fungal phytase that can be used in poultry diet as a cheapest source of digestibility improving agent