The effective diffusion coefficient of oxygen, IDe, was determined in different gel support materials (calcium alginate, ~-carrageenan, gellan gum, agar and agarose) which are generally used for immobilization of cells. The method used was based upon fitting Crank's model on the experimental data. The model describes the solute diffusion from a well-stirred solution into gel beads which are initially free of solute. The effect of the gel concentration on ID e of oxygen in the gel was investigated. The results showed a decreasing ID e for both agar and agarose at increasing gel concentration. In case of calcium alginate and gellan gum, a maximum in ID e at the intermediate gel concentration was observed. It is hypothesized that this phenomenon is due to a changing gelpore structure at increasing gel concentrations. The ID e of oxygen in calcium alginate, ~c-carrageenan and gellan gum varied from 1.5"10 -9 to 2.

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