IMMOBILIZATION OF BURKHOLDERIA-CEPACIA IN POLYURETHANE-BASED FOAMS - EMBEDDING EFFICIENCY AND EFFECT ON BACTERIAL-ACTIVITY

Immobilization of the trichloroethylene-degrading bacterium Burkholder ia cepacia was evaluated using hydrophilic polyurethane foam. The infl uence of several foam formulation parameters upon cell retention was e xamined. Surfactant type was a major determinant of retention; a lecit hin-based compound retained more cells than pluronic- or silicone-base d surfactants. Excessive amounts of surfactant led to increased washou t of bacteria. Increasing the biomass concentration in the foam from 4 .8 to 10.5% dry weight per wet weight of foam resulted in fewer cells being washed out. Embedding at reduced temperature did not significant ly affect retention, while the use of a silane binding agent gave inco nsistent results. The optimal formulation retained all but 0.2% of tot al embedded cells during passage of 2 L of water through columns conta ining 2 g of foam, All foam formulations tested reduced the culturabil ity of embedded cells by several orders of magnitude, but O-2 consumpt ion and CO2 evolution rates of embedded cells were never less than 50% of those of free cells. Nutrient amendments stimulated an increase in cell volume and ribosomal activity in immobilized cells as indicated by hybridization studies using fluorescently labeled ribosomal probes. These results indicate that, although immobilized cells were mostly n onculturable, they were metabolically active and thus could be used fo r biodegradation of toxic compounds.