:The e †ect of anionic (sodium butylbenzene sulfonate, sodium butylmonoglycol sulfate), cationic (tetrabutyl ammonium bromide), nonionic(Tween 20) and amphoteric (proline) surface active additives on the partitioning of proteins and enzymes, such as BSA, lysozyme, glucose oxidase and b-lactoglobulin, in a bipolymeric aqueous two-phase system of polyethylene glycol and dextran has been studied. The partitioning of proteins and enzymes in the aqueous twophase system is inÑuenced by surface active additives depending upon their structure and charge. The amphiphiles themselves partition unevenly between the two phases. Their e †ect on protein partitioning can be explained on the basis of electrostatic and hydrophobic interactions. In the presence of ionic amphiphiles, proteins have an affinity for the other phase if an amphiphile carrying a charge of the same sign partitions to that phase. The hydrophobic e †ect contributes to protein partitioning if the proteins have signiÐcant members of surface hydrophobic amino acid residues.

Crude porcine pancreatic lipase was puriÐed by removing waterinsoluble impurities (residual lipid material) associated with it by a conventional method, using hydrotropic additives and by liquid coacervate extraction. Maximum yield with good recovery of activity was obtained when hydrotropes were used to separate the associated lipids from lipase. The thermostability of the enzyme was also checked in the solutions of additives such as sodium butyl monoglycol sulfate (Na-BMGS), proline and Triton X-114. In Na-BMGS solutions above a concentration of 0É2 mol dm~3 the lipase activity decreased beyond 50¡C whereas in 1 mol dm~3 proline solution it was retained even at 80¡C, showing a good thermostabilizing e †ect. However, in the presence of Triton X-114 the enzyme was completely inactivated with increase in temperature.1998 SCI. ( J. Chem. T echnol. Biotechnol. 71, 155È161 (1998)

The effect of cationic and anionic surface active additives on the partitioning of proteins has been studied. The surface active agents interact with proteins electrostatically and also hydrophobically. The increased hydrophobicity of the proteins because of association with surfactants is responsible for the changes in the partition coefficients and in some cases for precipitation of the proteins. Specific interactions also exist between mildly surface active amino acids and proteins.

: Crude porcine pancreatic lipase was puriÐed by removing waterinsoluble impurities (residual lipid material) associated with it by a conventional method, using hydrotropic additives and by liquid coacervate extraction. Maximum yield with good recovery of activity was obtained when hydrotropes were used to separate the associated lipids from lipase. The thermostability of the enzyme was also checked in the solutions of additives such as sodium butyl monoglycol sulfate (Na-BMGS), proline and Triton X-114. In Na-BMGS solutions above a concentration of 0É2 mol dm~3 the lipase activity decreased beyond 50¡C whereas in 1 mol dm~3 proline solution it was retained even at 80¡C, showing a good thermostabilizing e †ect. However, in the presence of Triton X-114 the enzyme was completely inactivated with increase in temperature.1998 SCI. ( J. Chem. T echnol. Biotechnol. 71, 155È161 (1998)

The effect of cationic and anionic surface active additives on the partitioning of proteins has been studied. The surface active agents interact with proteins electrostatically and also hydrophobically. The increased hydrophobicity of the proteins because of association with surfactants is responsible for the changes in the partition coefficients and in some cases for precipitation of the proteins. Specific interactions also exist between mildly surface active amino acids and proteins.