Degradation of caffeine by immobilized cells of Pseudomonas putida strain C 3024

Summary

A caffeine-resistant strain of Pseudomonas putida was isolated from soil and was grown with caffeine as the sole source of carbon, energy and nitrogen. Cells were immobilized in agar gel particles which were continuously supplied with a caffeine solution (0.52 g · l⁻¹, D=1.0 h⁻¹) in a homogeneously mixed aerated reaction vessel. In the presence of the ATPase inhibitor arsenate the caffeine was removed by the immobilized cells at an average rate of 0.25 mg caffeine · h⁻¹ · (mg cell carbon)⁻¹ during 6 days. Thereafter a rapid decline of activity was observed. From a similar system without arsenate supplied with a growth medium containing a limiting amount of caffeine (0.13 g · l⁻¹) the caffeine was almost completely oxidized by the immobilized cells. The concentration of the remaining caffeine was 1.4 mg · l⁻¹, which is much lower than the substrate constant for caffeine (9.7 mg · l⁻¹) observed with freshly harvested suspended resting cells.