Brij® Ethoxylated fatty alcohols

The catalytic behavior and the stability of enzymes in reverse micelles are highly dependent on the composition and the structure of the micioanulsion. The activity of entrapped enzymes strongly depends on the water content, the nature of the organic solvent, as well as the nature and the concentration of surfactant. Various surfactants, including the anionic AOT, the cationic CTAB, nonionics such as Triton, Brij, ethoxylated fatty alcohols, and zwitterionic phospholipids (phosphatidylcholine), were used for the preparation of reverse miceUar systems-containing enzymes (Table 13.1). Most inveshgated systans used AOT as the surfactant because its phase behavior is well understood. The activity of some enzymes has been reported to depend on the surfactant concentration and in some cases it was attributed to the interaction of the enzymes with the miceUar membrane [8,26,27]. Recent developments in this area inclnde the use of modified surfactants or their mixtures with other additives and cosurfactants such as alcohols and sugars or the use of aprotic solvents for the reduction of the ionic interactions between the enzyme molecules and the micellar interface in order to improve the enzyme catalytic behavior and operational stabihty [8,17,28-34]. 

The commercial nonionic surfactants used in this study included two alcohol ethoxylates, Witconol SN120 (Witco Corp., New York NY) and Brij 35 (ICI, Wilmington, DE), and an ethoxylated sorbitan fatty acid ester, Tween 80 (ICI). Brij 35 was purchased from Sigma (St. Louis, MO), while SN120 and Tween 80 were provided by their respective manufacturers. All surfactants were used as received. 

---