Purification of alkaline protease from chicken intestine by aqueous two phase system of polyethylene glycol and sodium citrate

An aqueous two phase system of polyethylene glycol (PEG) and salts was evaluated for separation and purification of alkaline proteases from chicken intestine. Among the different salts evaluated potassium phosphate and sodium citrate gave higher enzyme yield (73.5% and 69.7% respectively) and enzyme purification (5.3 and 7.4 fold) in PEG rich upper phase. Increase in concentration of sodium citrate in the system resulted in reduction in enzyme yield and enzyme purification factor, with 15% salt showing highest enzyme yield (59.8%) and purification (6.7 fold). Initial protein concentration in the system did not show any specific trend on the partition behavior of the enzyme. The temperature at which the system is incubated did not show any significant (p ≥ 0.05) effect on enzyme partition and purification. Increasing the PEG concentration in the system from 15 to 25% resulted in reduction in enzyme yield from 53.7 to 21.9% and enzyme purification from 5 fold to 1.4 fold in PEG rich upper phase. pH also had a significant (p < 0.05) effect on the partition of the enzyme to the upper phase with highest purification (3.4 fold) at pH 9.0 and higher enzyme yield (46.2%) at pH 10.