Purification of an α-amylase inhibitor in a polyethylene glycol/fructose-1,6-bisphosphate trisodium salt aqueous two-phase system

A novel aqueous two-phase system of polyethylene glycol (PEG)/fructose-1,6-bisphosphate (FBP) trisodium salt was employed to purify an α-amylase inhibitor (α-AI) from wheat flour after failure in use of the conventional aqueous two-phase systems of PEG/(NH₄)₂SO₄ and PEG/dextran (DEX). Phase compositions including PEG molecular weight and concentration of PEG, fructose-1,6-bisphosphate trisodium salt concentration, as well as pH of the system affected the partition of α-AI. The inhibitor was obtained with a purification factor of 3.2 and recovery of 79% by using 11.7% (w/w) of PEG2000 and 19% (w/w) of fructose-1,6-bisphosphate trisodium salt at pH 7.0 in the top phase.