alpha-Chymotrypsin and lysozyme were solubilized in a water/O-[(2-tridecyl, 2-ethyl-1,3-dioxolan-4-yl)methoxy]-O'-methoxy poly(ethylene glycol) (CK-2,13 surfactant)/isooctane water-in-oil microemulsion solution at 1.5-2 and 10 g l(-1) for 0.15 and 1.2 M CK-2,13, respectively. Upon contact with an equal volume of 0.1 M NaH2PO4/Na2HPO4 buffer, pH 5, a three-phase system (Winsor-III system) was formed, consisting of a surfactant-rich middle phase and aqueous and isooctane-rich "excess" phases. Both enzymes were rapidly released into the aqueous excess phase, with 70% recovery of each in 30 and 60 min for microemulsion solutions containing 0.15 and 1.2 M surfactant, respectively. The recovered enzymes retained > 90% of their original specific activity.