Fluidized bed bioartificial liver has been proposed as a temporary support to bridge patients suffering from acute liver failure to transplantation. In such a bioreactor, alginate beads hosting hepatocytes are in continuous motion during at least six hours. After having shown in vitro the functionality of such a device, the present study aims at analyzing the potential mechanical alterations of the beads in the bioreactor, perfused by different surrounding media. Compression experiments are performed and coupled for analysis with Hertz theory. They provide qualitative and quantitative data. The average value of the shear modulus, calculated for the different cases studied varied from 2.4 to 10.4 kPa, and could therefore be considered as a quantitative measure of the beads mechanical properties. From the compression experiments and the estimated values of the shear modulus, we could now evaluate the effect of different operating conditions (fluidization, presence of cells, surrounding medium) on the mechanical behavior of alginate beads. On the one hand, the motion during six hours in the bioreactor does not alter the beads significantly. On the other hand, the presence of different substances in the fluid phase might change their mechanical strength. These results can be considered as new encouragements to use such a device as a bioartificial organ.