A stainless steel mesh packing with 99.0% porosity was installed in the riser section of an external loop airlift bioreactor (ELAB) to develop a new bioreactor that is a combination of a traditional ELAB and a packed-bed bioreactor. The gas holdup and mass-transfer rates of three volatile organic chemicals (VOCs) were studied in this ELAB, both with and without the packing. When the packing was used, the overall volumetric mass-transfer coefficient increased to values of 0.005 and 0.004 s(-1), an average increase of 65.1% and 33.4% for toluene and benzene, respectively. The packing increased gas holdup and decreased bubble size in the bioreactor, both contributing to the improvements in the mass-transfer rates. A difference was observed between absorption and desorption rates of VOCs, which was explained by the change in gas bubble sizes in the presence of VOCs. A dynamic spatial model was used to predict the transient concentration distribution in the ELAB with and without a packed bed. The mass-transfer coefficient was determined as a best-fit parameter of the model. This dynamic model was compared to simulations of the ELAB as a completely stirred reactor, and the dynamic spatial model demonstrated greater accuracy for prediction of the mass-transfer rates at all operating conditions.