Recent Advances in Biodegradation of High-molecular Weight PAHs in Soil

Bioremediation is a promising technique for eliminating polycyclic aromatic hydrocarbons(PAHs) from contaminated soil.The microbial biodegradation mechanisms of high-molecular weight polycyclic aromatic hydrocarbons(HMW)-PAHs in soils were reviewed with special emphasis on the principles and difficulties of bioremediation of PAH-contaminated soil.Some genera of microorganisms able to utilize HMW-PAHs as the sole carbon and energy source have been isolated.Most of them are mainly single strains which can metabolically degrade four-ring PAHs,and some of them can co-metabolize five-ring PAHs.Low bioaccessibility of HMW-PAHs is a difficulty in the bioremediation of contaminated soil.Release of surfactants,formation of biofilms and production of extracellular polymeric substances by some of the PAH-degrading bacteria can enhance the bioaccessibility of PAHs and therefore accelerate the biodegradation.Combination of bacteria and fungi can increase their in situ bioremediation efficiency.Therefore,bioremediation is an environmentally friendly,economic suitable and sustainable technique for eliminating PAHs from soil.