Enhanced biodegradation of poorly available polycyclic aromatic hydrocarbons by easily available one

The objective of the study was to test the hypothesis that easily available polycyclic aromatic hydrocarbons (PAHs) can stimulate the biodegradation of poorly available PAHs. Therefore, the biodegradation of poorly available PAHs was carried out, with easily available ones as the growth substrate using two phenanthrene-degrading bacteria, Micrococcus sp. PHE3 and Sphingobium sp. PHE9, in a two-liquid phase system (TLPs). Firstly, although anthracene, fluoranthene and pyrene could not be consumed by the monoculture as the sole carbon and energy sources, all of them could be biodegraded when naphthalene (NAP) or phenanthrene (PHE) served as the growth substrate, demonstrating that the spiking of easily available PAHs enhanced biodegradation of poorly available ones. However, fluoranthene could not be biodegraded by Micrococcus sp. PHE9 with PHE as the growth substrate, or by Sphingobium sp. PHE3 using NAP and PHE as the growth substrates, indicating that the growth substrate affected the bacterial utilization of poorly available PAHs. Furthermore, a metabolite, 1,2-dihydroxynaphthalene, was identified when NAP served as the growth substrate. In contrast, no metabolite was detected when PHE was used as the growth substrate. These results exhibited significant implications for the bioremediation of PAHs-contaminated soils.