THEORETICAL-ANALYSIS OF ACTIVE-TRANSPORT THROUGH A REVERSED BIENZYME POROUS MEMBRANE - I - TRANSPORT OF A NEGATIVELY CHARGED, SMALL, HYDROPHILIC MOLECULE

A mathematical model of the active transport of a negatively charged, small molecule through a reversed bienzyme porous membrane separating two compartments, recently presented, was analyzed. This model involve d 13 identified parameters. The main parameters were studied both in t erms of their impact on the final substrate surconcentration ratio (SR ) and on the final product pollution level (PL) expected in a receivin g compartment. Our analysis demonstrates that, with the topography inv olved, the active transport of a given negatively charged, small molec ule only occurs provided that the three key factors act together and s imultaneously: (i) bound reversed enzyme activities must exist at the pore entrance/exit; (ii) the first enzyme of the reactive sequence inv olved acts in an unstirred layer facing the feed compartment; (iii) th e negatively charged molecules to be transported must be repelled by t he negative charges on the membrane. Furthermore, our analysis permitt ed us to differentiate between the two different roles played by the t wo unstirred layers. It was found that the unstirred layer facing the feed chamber governs the substrate SR expected in the opposite receivi ng chamber, while the unstirred layer facing the receiving chamber pla ys a role only on the kinetic behavior of this active transport-like p henomenon. Besides the new Light brought on biological transport syste ms, this study may be of great interest for the improvement of the per formances of a bioreactor/separator device. (C) 1998 Elsevier Science B.V.