Metagenomic analysis of facilitation mechanism for azo dye reactive red 2 degradation with the dosage of ferroferric oxide

Biological degradation of azo dyes and their intermediates requires a relatively long reaction duration due to their refractory characteristics. To enhance the azo dye degradation, the effects of ferroferric oxide (Fe3O4) on organic carbon metabolism, azo dye degradation, and microbial community structures were investigated through metagenomic analysis. Microorganisms possessing the azo dye-degradation ability changed from Bacillus, Aeromonas, and Lysobacter to Acinetobacter and Desulfovibrio when the Fe3O4 dosage increased from 0 g L to 15 g L. Geobacter and Staphylococcus were the most important bacteria involving in organic carbon metabolism, electron transfer, and azo dye degradation, and the dosage of Fe3O4 could enrich both microorganisms and enhance system performance. The facilitation mechanism with the dosage of Fe3O4 could be attributed to the increase of extracellular electron transfer rate and the enrichment of functional microorganisms.