Purification of trypsin by affinity precipitation and combining with aqueous two-phase extraction

Soybean trypsin inhibitor was bound to a pH-sensitive reversibly soluble-insoluble polymer (AS-L) for affinity precipitation of trypsin. Trypsin was purified from a crude extract 5.4-fold and with 61% yield, however, the reusability of the ligand was poor. This can be overcome by combining aqueous two-phase extraction with affinity precipitation, which improved trypsin yield and purity factor after repeated ligand usage.