Dynamic changes in reactive oxygen species (ROS) of Taxus cuspidata cells immobilized on polyurethane foam were investigated and the relation between ROS content and taxol production was discussed. Immobilization shortened the lag period of cell growth and moderately increased H2O2 and O2-* contents inside the microenvironment within the first 15 d. After 20 d, excessive production of H2O2 and O2-* was observed accompanied by marked increases in membrane lipid peroxidation and cell membrane permeability. The taxol content of immobilized cells was fourfold that of suspended cells at d 35. The addition of exogenous H2O2 barely affected malondialdehyde content and cell membrane permeability but led to an obvious accumulation of taxol. It is inferred that the intracellular and extracellular H2O2 inside the microenvironment might be one factor promoting taxol biosynthesis under the immobilization stress.

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Distinct spatio-temporal variations of metal ions and Taxol production were observed for Taxus cuspidata cells immobilized on polyurethane foam. The Taxol content in the inner foam layer reached 215 microg g(-1) at day 30, which was 40-fold higher than that in the outer foam layer, and the Ca2+ and Mg2+ contents were 5.3 and 3.7 times higher, while the K+ content was 5.5 times lower. Thus higher intracellular Ca2+ and Mg2+ contents and lower intracellular K+ content may favor the Taxol biosynthesis in immobilized Taxus cuspidata.