ISOLATION, SCREENING OF PHYTATE DEGRADING FUNGI (ASPERGILLUS NIGER) AND OPTIMIZATION OF SUBMERGED FERMENTATIVE PRODUCTION OF PHYTASE

Abstract

Microbial phytases are having several applications and one of the important application is it can be used
as an animal feed supplement, not only to improve phytate digestibility and nutritive value of plant based
foods but also reduces the environmental phosphorus pollution. In the present study, 12 fungal strains
were isolated from different poultry soil wastes (Tirupati & surrounding areas) and screened for phytase
activity by using phytase screening medium (PSM). Among the isolates one strain was found to possess
potent phytase producing activity and identified as Aspergillus niger which has been selected for further
studies. Phytase production by A.niger was evaluated in submerged fermentation. Effect of different
culture media on phytase production was assessed and fermentation parameters were optimized.
Physical parameters (temperature, pH), chemical parameters (different carbon and nitrogen sources and
mineral salts) Optimization studies were studied. Maximum phytase activity of 465 U/ml was found at
30°C in submerged cultivation. The activity was found to decline above 30°C. The fungus failed to grow
above 50°C. Phytase was most active at pH 5 (456 U/ml) with an increase in the pH of the medium
enzyme activity declined. Optimization studies indicated that glucose was more suitable carbon source for
maximum (478 U/ml) phytase production. Various nitrogen sources were used in optimization process
where peptone has exhibited maximum activity of 482U/ml. It was found in our results that all the metal
salts (sodium chloride, magnesium sulphate, manganese sulphate and copper sulphate) used in the
study had a negative impact on the enzyme production.