Extraction of enzymes and their activities in AOT reverse micellar systems modified with nonionic surfactants.

Abstract

The extraction of Chromobacterium viscosum lipase and α-chymotrypsin from aqueous solution, and hydrolysis catalyzed by these enzymes were carried out in AOT/Span 60 and in AOT/Tween 85 mixed reverse micellar systems. Span 60 was likely to be solubilized in the water pool of AOT micelles without any change in micellar shape, while Tween 85 brought about an elongation of the micellar shape. The extracted fraction of the α-chymotrypsin at pH 6 was decreased by the addition of Span 60 or Tween 85, owing to the dilution of negative charge density of micelles. However, the extracted fraction of the lipase was increased by the addition of Tween 85, which seemed to act as an affinity ligand. The activity of α-chymotrypsin was improved by the addition of Span 60 or Tween 85, which decreases the electrostatic and hydrophobic interaction with AOT molecules. The activity of the lipase was significantly improved by the addition of Tween 85, especially in the higher range of water content, and the bell-shaped dependence of the activity on the water content disappeared. The lipase activity was maximum when the molar ratio of AOT to Tween 85 was 3:2–4:1.