One-step separation of β-galactosidase from β-lactoglobulin using water-in-oil microemulsions

► W/o microemulsions extract impurity proteins from β-galactosidase (β-gal) in one-step. ► Solubilisation studies determine microemulsion conditions for excluding β-gal. ► Mixtures contained β-gal and impurity protein (β-Lg) with similar pI but lower MW. ► Microemulsions with [buffer] >40 mM and added KCl extract β-Lg, expel purified β-gal. ► At 100 mM [KCl], process yields virtually pure β-gal with 92% activity recovery.