Airlift Reactors may present an alternative to fluidized bed bioreactors, with integrated alginate beads in order to immobilize hepatocytes for bioartificial liver use. The present study was aimed to examine the bi-directional mass transfers of the marker Vitamin B-12 between the surrounding fluid and the empty alginate beads. A simplified mathematical model based on Fick's first law was applied to describe diffusive mass transfer at the interface between the fluid and the beads calculating the overall mass transfer coefficients for both static and dynamic experimental conditions. Comparing with the Fluidized Bed Reactor, the more shear enhanced diffusion coefficient for Vitamin B-12 was 1.5 times higher verifying the efficiency of such a device. Increased shear rates in Airlift Reactors are provoked by additional turbulences due to the rising bubbles. Furthermore, it could be proven that the overall mass transfer mainly depends on the relative velocity between the external fluid and the alginate beads. (C) 2008 Elsevier B.V. All rights reserved.