Enhanced biodegradation of sediment-bound heavily weathered crude oil with ligninolytic enzymes encapsulated in calcium-alginate beads.

The degradation of crude and weathered crude oil following the application of crude and calcium-alginate encapsulated ligninolytic enzymes was studied using in situ microcosms. Changes in the chemical composition of the oil were monitored in crude enzyme extracts, as well as a sediment matrix, for as long as 70 days. Compound-specific effects of ligninolytic enzymes applied to the sediments were observed over time through changes in concentration of total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs) and fractions of saturates, aromatics, resins and asphaltenes (SARA). As the oil weathered, most TPH and PAH fractions showed a rapid decrease in concentration. As sediment oil concentrations decreased following treatment with ligninolytic enzymes, the microbial population was enriched with hydrocarbon-degrading species. This trend demonstrates that the oil fractions initially not bioavailable for microbial degradation, were subsequently released to the sediment via catalytic conversion with laccase and manganese peroxidase, and the oil continues to be biodegraded by microbial populations.

Oil Biodegradation and Oil-Degrading Microbial Populations in Marsh Sediments Impacted by Oil from the Deepwater Horizon Well Blowout.

To study hydrocarbon biodegradation in marsh sediments impacted by Macondo oil from the Deepwater Horizon well blowout, we collected sediment cores 18-36 months after the accident at the marshes in Bay Jimmy (Upper Barataria Bay), Louisiana, United States. The highest concentrations of oil were found in the top 2 cm of sediment nearest the waterline at the shorelines known to have been heavily oiled. Although petroleum hydrocarbons were detectable, Macondo oil could not be identified below 8 cm in 19 of the 20 surveyed sites. At the one site where oil was detected below 8 cm, concentrations were low. Residual Macondo oil was already highly weathered at the start of the study, and the concentrations of individual saturated hydrocarbons and polycyclic aromatic hydrocarbons continued to decrease over the course of the study due to biodegradation. Desulfococcus oleovorans, Marinobacter hydrocarbonoclasticus, Mycobacterium vanbaalenii, and related mycobacteria were the most abundant oil-degrading microorganisms detected in the top 2 cm at the oiled sites. Relative populations of these taxa declined as oil concentrations declined. The diversity of the microbial community was low at heavily oiled sites compared to that of the unoiled reference sites. As oil concentrations decreased over time, microbial diversity increased and approached the diversity levels of the reference sites. These trends show that the oil continues to be biodegraded, and microbial diversity continues to increase, indicating ongoing overall ecological recovery.