Based on experimental data from fermentation runs, as well as from L-phenylalanine (L-Phe) separation studies, a simple model is presented that describes the total ISPR approach for on-line L-Phe separation. While fermentation process modeling via a macrokinetic model revealed an L-Phe inhibition constant of 20 +/- 1.35 g/L using recombinant E. coli cells, the reactive-extraction process modeling identified the L-Phe cation diffusion in the aqueous donor film and the transport of the lowly soluble carrier/ L-Phe complex in the aqueous acceptor film as the most dominant transfer steps. The corresponding mass transfer coefficients were estimated as k(PheD) = 128 x 10(-7) cm/s (extraction) and k(CPheA) = 178 x 10(-5) cm/s (back-extraction). Simulation studies were performed for the total ISPR approach, which gave hints for strategies of further process optimization.