Application of supported liquid membranes containing methyl cholate in cyclohexane for the carrier-mediated transport of sugars

摘要

A supported liquid membrane (SLM) containing methyl cholate,a bile acid ester,as carrier for the facilitated transport of sugars has been prepared with cyclohexane as a solvent instead of the previously used aromatic solvents,opening the way to industrial applications.The SLM consists of a microporous poly(vinylidene difluoride) support impregnated with a solution of carrier (C).The transport of several commercial sugars and deoxy-sugars has been studied.The initial flux J_i of sugar (S) shows a linear dependence on [C]_0,the concentration of carrier,but behaves according to the saturation law with respect to c_0,the initial concentration of sugar in the feed phase.Thus,the rate-determining step of the transport is the migration within the SLM of a carrier-sugar complex (CS) formed rapidly at the interface between the SLM and the feed solution.The apparent diffusion coefficient D* and the equilibrium constant K of the complex have been determined for each sugar,revealing noticeable differences that confirm molecular recognition by the HO-3,7,12 triol system of methyl cholate.The complexes of D-xylose,L-rhamnose and L-fucose,three sugars that do not possess an HO-6 group,are weaker than those of the corresponding hexoses,i.e.glucose,mannose and galactose.The importance of the presence of the exocyclic HOCH_2 group for efficient binding of the sugar may be related to the long distance between HO-3,12 of the carrier.