Paclitaxel and baccatin III-producing cells of Taxus baccata were immobilized within Ca2+ -alginate beads. Under established optimum conditions for the biosynthesis of both taxanes, the yields of paclitaxel and baccatin III in shake-flask cultures of free cells increased by factors of up to 3 and 2, respectively, in the corresponding cultures of immobilized cells. Although the scale-up from shake-flask to bioreactor culture usually results in reduced productivities when both free and immobilized cells were grown in the same optimum conditions in three different bioreactor types (Stirred, Airlift, and Wave) running for 24 days in a batch mode and with the system optimized in each case, there was a considerable increase in the yields of paclitaxel and baccatin III. Among the reactors, the Stirred bioreactor was the most efficient in promoting immobilized cell production of paclitaxel, giving a content of 43.43 mg.L-1 at 16 days of culture, equivalent to a rate of 2.71 mg.L-1.day(-1). To our knowledge, the paclitaxel productivity obtained in this study is one of the highest reported so far by academic laboratories for Taxus species cultures in bioreactors. (C) 2005 Wiley Periodicals, Inc.