English to Spanish Science Biology (-tech,-chem,micro-) biochemistry

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Immobilization of the trichloroethylene-degrading bacterium Burkholderia cepacia was evaluated using hydrophilic
polyurethane foam. The influence of several foam formulation parameters upon cell retention was examined. Surfactant
type was a major determinant of retention; a lecithin-based compound retained more cells than pluronic- or
silicone-based surfactants. Excessive amounts of surfactant led to increased washout 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 significantly affect retention, while the use of a silane
binding agent gave inconsistent results. The optimal formulation retained all but 0.2% of total embedded cells during
passage of 2 L of water through columns containing 2 g of foam. All foam formulations tested reduced the culturability
of embedded cells by several orders of magnitude, but O2 consumption 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 nonculturable, they were metabolically
active and thus could be used for biodegradation of toxic compounds.