Biodegradation of p-nitrophenol and 4-chlorophenol by Stenotrophomonas sp.

A bacterium named LZ-1 capable of utilizing high concentrations of p-nitrophenol (PNP) (up to 500 mg L-1) as the sole source of carbon, nitrogen and energy was isolated from an activated sludge. Based on the results of phenotypic features and phylogenetic similarity of 16S rRNA gene sequences, strain LZ-1 was identified as a Stenotrophomonas sp. Other p-substituted phenols such as 4-chlorophenol (4-CP) were also degraded by strain LZ-1, and both PNP and 4-CP were degraded via the hydroquinone pathway exclusively. Strain LZ-1 could degrade PNP and 4-CP simultaneously and the degradation of PNP was greatly accelerated due to the increased biomass supported by 4-CP. An indigenous plasmid was found to be responsible for phenols degradation. In soil samples, 100 mg kg(-1) of PNP and 4-CP in mixtures were removed by strain LZ-1 (10(6) cells g(-1)) within 14 and 16 days respectively, and degradation activity was maintained over a wide range of temperatures (4-35 degrees C). Therefore, strain LZ-1 can potentially be used in bioremediation of phenolic compounds either individually or as a mixture in the environment.