The bacteriocin nisin was extracted in PEG/salt aqueous two-phase systems (
ATPS) using the property that the systems can extract hydrophobic proteins.
The concentrations of the phase-forming components, PEG 4000 and Na2SO4, w
ere optimized for nisin recovery by means of statistical experimental desig
ns, and it was found that they strongly influenced nisin recovery. The opti
mal composition of ATPS was found to be 15.99% (w/w) PEG 4000 and 15.85% (w
/w) Na2SO4 (pH 2), and the optimal ATPS allowed an 11.60% increase of nisin
recovery compared to the standard method of nisin assay.