PRODUCTION OF ANTHRAQUINONES BY IMMOBILIZED FRANGULA-ALNUS MILL PLANT-CELLS IN A 4-PHASE AIRLIFT BIOREACTOR

The production of anthraquinones by Frangula alnus Mill. plant cells w as used as a model system to evaluate the performance of a liquid-liqu id extractive product-recovery process. The shake flask experiments ha ve shown higher production of anthraquinones in cell suspension and fl ask cultures of calcium-alginate-immobilized cells when silicone oil w as incorporated into the medium, compared to a control without silicon e oil. An external-loop air-lift bioreactor, developed and designed fo r the production and simultaneous extraction of extracellular plant ce ll products, was regarded as a four-phase system, with dispersed gas, non-aqueous solvent and calcium-alginate-immobilized plant cells in Mu rashige and Skoog medium. Continuous extraction of anthraquinones by s ilicone oil and n-hexadecane inside the bioreactor resulted in 10-30 t imes higher cell productivity, compared to that of immobilized cells i n a flask. Based on the mixing pattern, immobilized biocatalyst extrap article and intraparticle diffusional constraints and the kinetics of growth, substrate consumption and product formation, a mathematical mo del was developed to describe the time course of a batch plant cell cu lture. The model showed satisfactory agreement with four sets of shake flask experiments and three bioreactor production cycles.