Rhizoremediation of mixed contaminated soil using Brassica napus and a bacterial consortium. NANO_Brassica

Physical and chemical approaches of soil remediation can be very effective but, frequently, at the expense of an unacceptable alteration of the soil ecosystem. In contrast, biological methods of soil remediation, which rely on the metabolic activity of microorganisms, plants or their combination, usually respect the integrity of the soil ecosystem. Here, we carried out a rhizoremediation experiment, using Brassica napus plants and a bacterial consortium (4 endophyte strains with plant growth-promoting traits: 3 Pseudomonas strains and 1 Microbacte-rium strain; 3 strains with the ability to degrade organic compounds: Paraburkholderia xenovorans strain LB400, Paenibacillus sp. and Lysinibacillus sp.) in mixed contaminated (hydrocarbons, PAHs, heavy metals) industrial soil treated with organic amendments for microbial biostimulation (composted horse manure vs. dried cow slurry). In addition, the mixed contaminated soil was supplemented with a rhamnolipid biosurfactant to enhance the removal of sorbed contaminants from soil, and linear alkyl benzene as inductor of hydrocarbon degradation. Apart from contaminant removal, we assessed the recovery of soil functioning through the determination of a variety of soil microbial indicators that reflect the biomass (microbial biomass carbon, total bacteria and fungi via qPCR), activity (potentially mineralizable nitrogen; enzyme activities: β-glucosidase, chitinase, β-xylosidase, phosphomonoesterase, leucine aminopeptidase, alanine aminopeptidase, arylsulphatase) and diversity (16S rRNA amplicon sequencing through next-generation sequencing) of soil microorganisms. Apart from a signifi-cant reduction in contaminant concentration, we detected a stimulation of soil microbial communities and, hence, soil functioning.