The production of anthraquinones by Frangula alnus Mill. plant cells was used as a model system to evaluate the performance of a liquid-liquid extractive product-recovery process. The shake flask experiments have shown higher production of anthraquinones in cell suspension and flask cultures of calcium-alginate-immobilized cells when silicone oil was incorporated into the medium, compared to a control without silicone oil. An external-loop air-lift bioreactor, developed and designed for the production and simultaneous extraction of extracellular plant cell products, was regarded as a four-phase system, with dispersed gas, non-aqueous solvent and calcium-alginate-immobilized plant cells in Murashige and Skoog medium. Continuous extraction of anthraquinones by silicone oil and n-hexadecane inside the bioreactor resulted in 10-30 times higher cell productivity, compared to that of immobilized cells in a flask. Based on the mixing pattern, immobilized biocatalyst extraparticle and intraparticle diffusional constraints and the kinetics of growth, substrate consumption and product formation, a mathematical model was developed to describe the time course of a batch plant cell culture. The model showed satisfactory agreement with four sets of shake flask experiments and three bioreactor production cycles.