Enhanced coastal soil bioremediation of petroleum hydrocarbons (PHCs) and associated microbial community transformation

Coastal contamination by petroleum-derived products has become a global concern in recent decades due to the intense anthropogenic activities of exploitation, transportation and processing of oil. Bioremediation, as an... [ view full abstract ]

Coastal contamination by petroleum-derived products has become a global concern in recent decades due to the intense anthropogenic activities of exploitation, transportation and processing of oil. Bioremediation, as an efficient, economical and environmentally sustainable solution to mitigate contamination and recover sites, has emerged as the most attractive biotechnology in restoring contaminated marine environments. Microbial degradation of petroleum hydrocarbons (PHCs) can be further enhanced by addition of nutrients and surfactants, which leads to the improvement of the mobility and bioavailability of PHCs. In this study, the enhanced soil bioremediation of PHCs and the associated microbial mechanisms were investigated. A systematic factorial design was conducted and a response surface reduced quadratic model was developed to determine the effects of nutrients and two surfactants (i.e., rhamnolipids and Tween 80) in the 36-day PHC degradation. A significant effect was observed from nutrient addition and a 92.3% removal of PHCs was achieved by applying rhamnolipids at a concentration of 150 mg/kg and nutrient solution at 1000 µL. Based on phospholipid fatty acid (PLFA) analysis, three different microbial transformation patterns were observed when the soils were treated by natural attenuation, enhanced by rhamnolipids, and by Tween 80, respectively. As indicated by PLFA biomarkers of the Gram-negative bacterial populations (cy17:0, cy19:0, 16:1ω7c and 18:1ω7c), Gram-negative bacteria are closely correlated with the amount of total soil biomass and are the sources of hydrocarbon degraders. PLFA compositional characteristics were also used to evaluate the physiological status of the indigenous microorganisms and elucidate biodegradation mechanisms linked to different soil treatments.