Determination of the effective diffusion coefficient of oxygen in gel materials in relation to gel concentration

The effective diffusion coefficient of oxygen, IDe, was determined in different gel support materials (calcium alginate, κ-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 IDe of oxygen in the gel was investigated. The results showed a decreasing IDe for both agar and agarose at increasing gel concentration. In case of calcium alginate and gellan gum, a maximum in IDe 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 IDe of oxygen in calcium alginate, κ-carrageenan and gellan gum varied from 1.5*10−9 to 2.1*10−9 m2s−1 in the gel concentration range of 0.5 to 5% (w/v).