Metagenomic analysis of aromatic ring-cleavage mechanism in nano-Fe3O4@activated coke enhanced bio-system for coal pyrolysis wastewater treatment

In current study, nano-Fe 3 O 4 @activated coke enhanced bio-system (FEBS) under limited-oxygen condition was applied for efficient treatment of aromatic organics in coal pyrolysis wastewater. Metagenomic analyses revealed functional microbiome linkages and mechanism involved in aromatic ring-cleavage. Based on biodegradation efficiency in different reactors, FEBS supplementation conferred the best organic removal (avg. 92.29%). It also showed a remarkable advantage in biodegradability maintenance (>   40%) over control reactors. Metagenomics profiling revealed the degradation processes were driven by Fe 3 O 4 redox reactions and microbial biofilm, while the suspended sludge was the principal force for aromatic mineralization . Based on the analysis of functional species and genes, most bacteria cleaved the benzene ring preferably through the aerobic pathways, mediated by catechol 1, 2-dioxygenase, catechol 2, 3-dioxygenase and protocatechuate 3, 4-dioxygenase (66−84%). Ecological network showed that Comamonas testosterone -centered microbiome and Azotobacter linked to the nitrogen (N)-heterocyclic ring-cleavage. Network linkage further demonstrated that Alicycliphilus and Acidovorax were the key tone taxa involved in benzene ring-cleavage. Finally, combined with analysis of degradation products , bacteria degraded N-heterocyclic ring containing organic aromatic compounds (quinoline) mainly through anaerobic processes , whereas cleavage of benzene ring preferred aerobic pathways. The enriched functional species were the primary reason for the enhanced biodegradation in FEBS.