Abstract
Aim of the present study was to isolate phytase producing Aspergillus niger, and production, purification and characterization
of phytase enzyme which is responsible for conversion of organic phosphorous (phytate) into inorganic form (available).
Indigenous A. niger isolates (n=20) were identified through macroscopic (obverse side: brown to black, granular, folded,
cottony from center with smooth and white edges, reverse side: center light pale, opaque edges and ridges) and microscopic
characteristics (phialospores in chains, circular vesical, metullae, phialids, septate and hyaline hyphae). Isolates were screened
for their ability to produce phytase on Phytase Screening Medium. Nine isolates (45%) gave positive screening results through
cobalt chloride staining (2% cobalt chloride, 6.25% ammonium molybdate and 0.42% ammonium vanadate). Diameter of
colonies, zone of hydrolysis and zone of hydrolysis to colony diameter ratio were 20.97- 43.00 mm, 25.03-49.00 mm and 1.13-
1.19, respectively. Phytase activity of cell free supernatants of indigenous A. niger isolates ranged from 68.88±2.55 to
274.99±10.14 FTU/mL. PASN01 and PASN06 exhibited highest enzyme activity (274.99±10.14 and 274.99±9.00 FTU/mL,
respectively). Phytase were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Molecular weights of
phytases from A. niger isolates ranged from 35.21 to 107.82 kilo Daltons. It is concluded that indigenous A. niger PASN01
and PASN06 may have commercial application after further characterization
