Development of a biofilm-forming bacterial consortium and quorum sensing molecules for the degradation of lignin-containing organic pollutants.

The presence of lignin along with other pollutants makes effluent more complex when it is discharged from Pulp and paper mills. The present study investigates the use of biofilm-forming bacteria isolated from pulp paper mill effluent contaminated sites (PPMECSs) for lignin degradation. Isolated biofilm-forming and lignin-degrading bacteria were identified as Bacillus subtilis, Enterobacter cancerogenus, and Bacillus licheniformis by 16S rRNA gene sequencing. Thin liquid chromatography (TLC) analysis showed that the consortium of bacteria produced acyl-homoserine lactone (AHL) as quorum sensing molecules and extracellular polymeric substances (EPS) that protect the bacterial consortium under unfavorable conditions. The potential consortium was able to reduce lignin (900 ppm) by 73% after 8 days of incubation in a minimal salt medium containing kraft lignin and glucose at pH 7.0 and 37 °C as compared to individual strains. The degradation by-products were identified as amides, alcohols, and acids. The major organic pollutants in the effluent were reduced after treatment of the constructed consortium, thus confirming active biotransformation and biodegradation of the lignin. Microscopic examination also indicated the presence of lignin induced biofilm formation. Hence, the constructed biofilm-forming bacterial consortia based on quorum sensing offered a sustainable and effective solution to treat lignin-containing complex pollutants.