Biodegradation kinetic rates of diesel-contaminated sandy soil samples by two different microbial consortia

Abstract

Mexico is one of the top oil-producing countries in the world and often suffers accidental oil spills, particularly in coastal regions. During the last decade, major spills have occurred in Mexican coastal ecosystems that have resulted in severely heavily oil-polluted shores. Although several remediation processes can be used, those with less servere negative consequences for the environment are preferred. Bioremediation through the use of specific microorganisms has been shown to speed up the decontamination rate process due to the ability of various microorganisms to split recalcitrant pollutants into smaller harmless molecules to be utilized as nutrients. Here, we present the effect of a microbial population succeeding in a bioremediation process carried out under laboratory conditions that may be suitable for the in situ decontamination of diesel in sandy soils. Two bacterial consortia isolated from heavily oil-polluted regions of Tabasco were able to utilize diesel as the sole carbon and energy source, degrading up to 98 % of the original concentration of oil within 30 days. Within 5 days, the bacterial consortia had reduced the levels of diesel in the experimental soil samples to the standard concentrations established by Mexican and U.S. environmental agencies (maximum contaminant level: 1200 mg/kg). Pyrosequencing-based assessment of the bacterial community structure of the two consortia revealed different compositions. Consortium CMic4 had a rich and diverse bacterial community, while CMic10 was dominated by Enterobacter sp., which represented 95.9 % of the community. Evaluation of the bioremediation efficiency by biocompatible decontamination analysis with earth worms confirmed the non-hazardous state of the treated soil after the decontamination process.