Biodegradation of fluorene at low temperature by a psychrotrophic Sphingomonas sp L-138

Sokolovska, I Wattiau, Pierre [UCL] Gerin, Patrick A. [UCL] Agathos, Spiros N. [UCL]

The ability of a psychrotrophic Sphingomonas sp. L-138 to assimilate fluorene was assessed and characterized in a liquid minimal medium at low temperature (12 and 20degreesC). Total fluorene mineralization was accomplished at both temperatures and the maximal rate of fluorene degradation was determined to be 4.8 mg dm(-3) d(-1) at 20degreesC and 3.2 mg dm(-3) d(-1) at 12degreesC. It was confirmed that this strain transforms the fluorene through the so-called ''five-membered attack'' and the expected metabolites of this pathway, 9-fluorenol, 9-fluorenone, phthalic acid, and protocatechuic acid, were detected in extracts of the culture broth. The specific growth rate of Sphingomonas sp. L-138 depends upon the initial fluorene concentration and it seems to be limited by the specific surface area of fluorene crystals. It was shown that the expression of the fluorene degradation pathway was found constitutive for this strain and did not depend on the substrate (glucose or fluorene) used in a pre-culture stage.