Tower reactors of a bubble column(0.085m³) and a three phase fluidized bed(TPFB, 0.114m³) were used for the batch production of exocellular polysaccharide xanthan with the aerobic bacteria Xanthomonas campestris. Even at high viscosities the fluidized particles of 8.0mm glass beads disintegrated the air bubbles, which led to about seven times higher gas-liquid mass transfer coefficient in the TPFB compared to that in the bubble column. On the other hand, the TPFB reactor could be operated in a limited range of xanthan concentrations due to the large bed expansion caused by a considerable increase in the effective viscosity of culture broths during a batch fermentation. Taking into account the high oxygen sorption efficiency(kg-O₂/kWh), the high energy input rate and the operation complexity, the TPFB bioreactor is expected to be appropriate for the continuous production of xanthan which shows constant rheological properties of culture broths at a steady state.