Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by microbial consortia enriched from mangrove sediments

Surface sediments from two mangrove swamps in Hong Kong were enriched to obtain PAH-degrading microbial consortia. The consortium from sediments enriched with phenanthrene (Phe) in Ma Wan, a mangrove swamp next to a boat anchorage, was effective in degrading PAH with 96.7% and 89.9% Phe degradation at 0 and 10 ppt salinities, respectively. The Phe-enriched microbial consortium could also use pyrene (Pyr) as the sole carbon source but the degradation was much less (around 15%). On the other hand, the Phe-enriched consortium from sediments in Yi O, a mangrove swamp recently polluted by an oil spill, completely removed Phe and Pyr at both 0 and 10 ppt salinities. This suggests that different consortia were selected in two sediments using the same PAH substrate. Not only sediments, PAH substrate used for enrichment also selected different consortia. The Pyr- and Fla-enriched Yi O consortia only achieved 10.5 and 4.5% Phe degradation, respectively and the corresponding pyrene degradation was 7 and 40%. Among the three PAH compounds, fluoranthene (Fla) was most difficult to degrade, and 21.1, 11.3, and 36.8% Fla were degraded by Phe-, Fla- and Pyr-enriched cultures, respectively.