Degradation of Alkane by Bacteria Immobilized on Polyurethane Foam

Immobilization of alkane-degrading bacteria by physical adsorption on polyurethane foam support was examined for application to the repeated degradation of alkane. Presence of hydrophobic substrate during cultivation promoted the attachment of alkane-degrading bacteria, such as Brevibacterium, Rhodococcus, and Pseudomonas sp., possibly due to the absorption of hydrophobic substrate on the polyurethane foam, followed by bacterial attachment to the substrate. Efficiency of immobilization depended on the hydrophobicity index, log P of the substrate. Various substrates, such as saccharides, triglycerides and fatty acids, were tested with log P in the range of -3.24 to 23.7. Triolein was the optimum substrate with the efficient immobilization and assimilation of microorganisms. Using cultivation with commercial salad oil as an inexpensive substitute for triolein, repeated batch degradation of n-tetradecane with the selected immobilized bacterium, Brevibacterium ketoglutamicum ATCC15587, could be continued for over 300 h with only slight loss of activity.