Extracellular phytase from Aspergillus niger CFR 335: purification and characterization.

Phytase, that is extensively used as a feed additive
is capable of hydrolyzing phytic acid, an antinutrient found in
about 60–80 % of all the plant commodities. This enzyme
improves the bioavailability of essential minerals such as
Ca2+, Mg2+, P, Zn2+, Fe3+, that are bound to phytic acid. An
extracellular phytase from a local fungal isolate, Aspergillus
niger CFR 335 was purified to homogeneity through a threestep
column chromatography using DEAE-Sephadex anion
exchanger. An active fraction of the enzyme was obtained
with NaCl gradient of 2.5Min DEAE Sephadex column. The
enzyme was purified up to 16 fold with a yield of 28.5 %.
Substrate specificity studies revealed a highest specific activity
of 32.6±3.1 U/mg for sodium phytate with the Km value of
0.08±0.1 mM. The molecular weight of the enzyme was
66 kDa with an optimum temperature of 30 °C and pH 4.5.
Up to 80 % of the activity was retained even after storing the
enzyme for 6 months at 4 °C.