Phytase assay
Phytase assay was performed according to the protocol of Heinonen and Lathi [14]. Enzyme assay was done in 40 μl volume at 37 °C for 30 min in 100 mM sodium acetate buffer containing 1 mM sodium phytate. The reaction was interrupted by adding 160 μl of freshly prepared acetone/5 N H2SO4/10 mM ammonium molybdate (2:1:1, v/v). Released inorganic phosphate was quantified spectrophotometrically by measuring the absorbance at 355 nm. Phytase activity unit is defined as the amount of enzyme that catalyzes the release of 1 μM of inorganic phosphorus from sodium phytate per minute. Concentration of protein was estimated by Lowry's method [15].