Designing a blended microbial culture to bioremediate distinct environmental matrices from a complex industrial site...

The contamination of soil and groundwater by amino-, nitro-, and chloroaromatics, which are compounds extensively used in chemical manufacturing, including pesticide production, poses significant risks due to their toxicity and mutagenicity. This study presents a proof-of-concept blended bacterial culture, developed by combining individual contaminant-degrading enrichments. The culture was tested for bioremediation of three contaminated environmental matrices from a former agrochemical site in northeastern Brazil: groundwater (total contaminant concentration: 100-1000 μM), soil (287-596 mg/kg), and highly contaminated water from overflow containment boxes (940-3153 μM). These matrices contained various pollutants, including 2-chloroaniline, 3-chloroaniline, 4-chloroaniline, 2,3-dichloroaniline, 3,4-dichloroaniline, 2,5-dichloroaniline, chlorobenzene, 1,2-dichlorobenzene, 2-chloronitrobenzene, 3-chloronitrobenzene, 4-chloronitrobenzene, 2,3-dichloronitrobenzene, 3,4-dichloronitrobenzene, and bis-(2-ethylhexyl)-phthalate (BEHP). Individual cultures tolerated at least five times the contaminant concentrations found in groundwater, while the blended microbial culture degraded up to 1.4 times the total contaminant load present at the site. Degradation occurred across all matrices. pH values from 4.0 to 6.5, as observed at the site, inhibited degradation, which resumed at near-neutral pH. At high concentrations, biodegradation required reinoculation and nitrogen amendment, demonstrating the need for combined bioaugmentation and biostimulation. Sediminibacterium dominated enrichments with 1,2-dichlorobenzene and 2,3-dichloronitrobenzene. Diaphorobacter dominated most individual cultures and the blended culture enriched with the contaminant mixture (up to 98.1 % relative abundance), occurring also in bioaugmented soils (0.6-6.9 %). Rhizorhapis (42.5 %) prevailed in BEHP-only soil treatment, whereas Caldalkalibacillus (43.4 %-47.5 %) dominated soil treatments containing amino-, nitro-, and chloroaromatic mixtures. These results demonstrate enriched blended cultures as a scalable approach to remediate diverse environmental matrices impacted by complex mixtures of amino-, nitro-, and chloroaromatic contaminants.