Performance and Microbial Community Analysis of Bioaugmented Activated Sludge System for Indigo Production from Indole

Indole is a typical nitrogen-containing aromatic pollutant in coking wastewater, and it can be used for the microbial production of indigo, one of the oldest dyestuffs. In this study, the activated sludge system bioaugmented with two indigo-producing bacterial strains, wild strain Comamonas sp. MQ and recombinant Escherichia coli (ND_IND), was constructed to investigate indigo bioproduction from indole. During the operation, the bioaugmentation could promote the production of indigo, especially in early stages, and the indigo yields gradually increased from 17.5 +/- 0.4 to 44.3 +/- 0.5 mg/L with the increase of influent indole (80 to 282 mg/L). Illumina MiSeq sequencing revealed that the microbial community could have a noticeable shift driven by the bioaugmentation and high indole pressure. The indigenous bacteria could be more responsible for indigo production, and the dominant genera Comamonas, Diaphorobacter, Paracoccus, Aquamicrobium, Pseudomonas, and Truepera could be the key functional taxa. Based on FAPROTAX (Functional Annotation of Prokaryotic Taxa) analysis, the nitrogen metabolism-related functional groups could play important roles in indole biotransformation and indigo biosynthesis. This study should provide insights into microbial production of indigo by microbial communities.