Immobilization of the surfactant-degrading bacterium Pseudomonas C12B in polyacrylamide gel. II. Optimizing SDS-degrading activity and stability. Enzyme and microbial technology

Conditions were established for optimizing the surfactant (SDS)-degrading activity of Pseudomonas C12B immobilized in polyacrylamide gel beads. Optimum activity was obtained by using immobilized cells derived from stationary phase of batch cultures and incubating with SDS at 30°C at pH 6.5. Half-saturation of the degradation system was achieved at an SDS concentration of 0.23 mM. Biocatalyst stability was highest for beads maintained in basal salts medium, retaining 91% of initial activity after 161 d. In Tris/HCl buffer or distilled water, the stability was much lower, although in all cases the stability of immobilized cells was higher than that of free cells under equivalent conditions. Biocatalyst beads “inactivated” by sequential incubation in three batches of distilled water containing only SDS could be reactivated by transferring beads to nutrient medium. Beads packed in a glass column and operated in a continuous up-flow mode using SDS/basal salts eluant produced 100% hydrolysis when run at retention times above 60 min. The system was highly stable in the continuous flow mode; when operated at a residence time of 55 min (initially giving 98% degradation), the extent of degradation decreased only slightly to 93% over a continuous operation period of 3 weeks.