Since a lethal effect of an increased temperature (42°C) on Pseudomonas putida strains PaW8 and PaW130 was demonstrated, strictly ionotropic gels such as calcium alginate or κ-carrageenan type X 0909 were used for cell co-immobilization, rather than a thermoionotropic κ-carrageenan gel. Among the variety of gel-dissolving solutions tested, only a 0.05M Na2CO3/0.02M citric acid solution was able to preserve around 100 % of the cell viability. A complete cell recovery was obtained from calcium alginate gel beads, while only 6 % of viable cells was recovered from the ionotropic κ-carrageenan gel.