A new technique is presented for the production of immobilized biocatalysts in large quantities. It consists of breaking up a jet of the biocatalyst/presupport mixture in uniform droplets by means of a resonance technique. Entrapment of yeast and plant cells in calcium alginate has been used as the model. The production capacity of the nozzles used (0.5, 0.8, and 1.1 mm exit diameters) is two orders of magnitude larger than the production capacity of the conventional techniques (maximum capacity with a 1.1-mm nozzle diameter is 24 L/h). Depending on frequency, nozzle diameter, and volumetric flow rate, the bead size varies between 1 and 2 mm, with standard deviations of 3-5% for yeast immobilization and 10-15% for plant cells. The deactivation of both yeast and plant cells is small and comparable to that found in the corresponding conventional procedures.

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.

No abstract

No abstract

The influence of support material (calcium alginate, x‐carrageenan and agarose), cell loading and, in case of alginate, bead diameter on the rate of respiration of immobilised plant cells (Daucus carota) was investigated. No significant differences were observed between the three supports and no loss of respiration activity occurred as result of immobilisation per se. The results show further that above a critical combination of cell loading and bead diameter limitations of the rate of respiration by diffusion of oxygen increases with increasing loading and diameter.