Effectiveness of a microbial formula, as a bioaugmentation agent, tailored for bioremediation of diesel oil and heavy metal co-contaminated soil

Abstract The activation of natural bioremediation potentials is the challenge that research is currently addressing for overcoming bottlenecks still affecting bioremediation applications. Bioaugmentation is one possible way to activate such natural potentials, provided that the biodiversity introduced to increase catabolically relevant capacity is identified also considering the ecological context. The present work deals with bioaugmentation aimed at the remediation of a soil co-contaminated (spiked) with both diesel oil (1%, v/w), and heavy metals (Pb and Zn), using intact soil core microcosms in different experimental conditions. We supposed that both heavy metal resistance and active metabolism towards organic pollutants are essential metabolic traits to trap the energetic flux, which drives the microbial community towards biodegradation under the given experimental conditions. Consequently, the bioaugmentation was performed by introducing a tailor made microbial formula composed of 12 allochthonous strains. They belong to a stable population previously isolated from a chronic polluted site and are both hydrocarbon degraders and heavy metal resistant and, also, compatible with the autochthonous microbial community. The active role of the microbial formula in pushing the entire community towards an effective bioremediation of diesel oil close to 75%, in the presence of bioavailable metals, has been proven through hydrocarbons analysis, metabolic and molecular profiling at community level (Biolog system, DGGE).