Activity of acetone-treated Chromobacterium viscosum lipase in AOT reverse micelles in the presence of low molecular weight polyethylene glycol

The activity of Chromobacterium viscosum lipase (glycerol-ester hydrolase, EC 3.1.1.3) entrapped in AOT/isooctane/water reverse micelles was significantly enhanced by pretreatment with acetone, using the hydrolysis of olive oil as a model reaction. The activity of acetone treated lipase was further enhanced when low molecular weight polyethylene glycol (PEG 400) was introduced into AOT reverse micelles. To know the effects of acetone treatment on the lipase activity in simple AOT and mixed AOT/PEG 400 reverse micelles, the influence of various parameters, such as W0 (molar ratio of water to surfactant), pH, surfactant concentration, ionic strength and reaction temperature were investigated and compared with those for native lipase in simple AOT reverse micelles. The optimal activities of treated lipase in AOT reverse micelles with and without PEG 400 were 2.0 and 1.6 times higher respectively than that of native lipase in AOT reverse micelles. A kinetic model that considers substrate adsorption equilibrium between the bulk phase of organic solvent and the micellar phase was successfully used to understand the improvement of the lipase activity. The Michaelis constant (Km) and substrate adsorption equilibrium constant (Kad) were obviously reduced compared with those for native lipase in AOT reverse micelles. The stability of the lipase in reverse micelles was also studied, and the values of half-life time (t1/2) were determined from residual activity profiles.