The influence of packed bed set in the riser section on the liquid-side volumetric mass transfer coefficient (K-L alpha(R)) in an external-loop airlift bubble column was examined with water, 20 wt% glycerol, 10 wt% ethanol and 0.3 wt% CMC aqueous solutions. The K-L alpha(R) was determined by the measurement of time-dependent oxygen concentration dissolved in the liquids. Bubble size, bubble rise velocity and gas holdup in the riser were measured to examine the effect of the packed bed using an optical fiber two-phase now system, The presence of the packed bed in the riser increased the K-L alpha(R) values for the liquids used. This was associated with the increase in the specific gas-liquid interfacial area due to bubble breakage by the packed bed. In addition, a correlation equation for K-L alpha(R) was proposed for both types of airlift bubble columns with and without the packed bed.