Enzyme purification with aqueous two-phase systems: comparison between systems composed of pure polymers and systems composed of crude polymers.

The main drawback when using aqueous two-phase systems for macromolecule purification is the high cost of most polymers used. The purification of an enzyme, alcohol dehydrogenase, from a crude extract of Saccharomyces cerevisiae was tested in systems composed of poly(ethylene glycol) and a crude hydroxypropyl starch or Reppal PES 100, a purified fraction of hydroxypropyl starch. Purification factors measured for the enzyme were very similar in both systems (between 0.8 and 1.4 for both systems in the upper phase). However, systems composed of Reppal PES present a greater recovery of enzyme, between 77% and 100% versus 60% and 100%, while systems composed of crude hydroxypropyl starch exhibit a larger delta log K for the tested ligand, 1.26 versus 0.81.