Immobilization of the surfactant-degrading bacterium Pseudomonas C12B in polyacrylamide gel beads: I. Effect of immobilization on the primary and ultimate biodegradation of SDS, and redistribution of bacteria within beads during use

The surfactant-degrading bacterium Pseudomonas C12B was immobilized in polyacrylamide gel beads. Conditions were established for minimizing the apparent loss of sodium dodecyl sulfate (SDS)-degrading activity accompanying polymerization, while still retaining durable gel beads. Apparent losses in SDS-degrading activity compared with free untreated bacteria were attributed largely to substrate diffusion limitations imposed by the gel matrix. Changes in the rate and extent of conversion of radiolabel from [1- 14C]SDS to 14CO 2 were attributed to diffusional restrictions on O 2 availability within the gel beads. Scanning electron microscopy was used to show that beads (3 mm 3) repeatedly exposed to SDS for 35 days contained a high cell density in a sub-surface layer 0.4–0.7 mm deep, with relatively few bacteria either at greater depth or at the bead surface.