Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium

• Published in: Journal of environmental management Vol. 356; p. 120623
• Main Authors: Tian, Fang, Guo, Guang, Fu, Weilian, Li, Shiji, Ding, Keqiang, Yang, Feng, Liang, Chengyue
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2024
• Subjects: Azo Compounds; Biodegradation, Environmental; Brilliant Crocein GR; Coloring Agents; Degradation pathway; Dioxygenases; Metagenome; NAD; NADP; Naphthalenesulfonates; Thermophilic consortium; Brilliant Crocein GR; Thermophilic consortium; Metagenome; Degradation pathway
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2024.120623

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50–75 °C), pH values of 6∼8, dye concentrations (100–400 mg/L) and salinities (1–5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min−1 mg−1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures. [Display omitted] •A novel thermophilic-halotolerant dye-decolorizing consortium was enriched.•The consortium BCGR-T can decolorize azo dye at 70 °C and 5% (w/v) salinity.•Caldibacillus and Aeribacillus were first discovered in BCGR decolorization consortium.•A new degradation pathway of BCGR by the consortium BCGR-T was proposed.•Functional genes involved in BCGR degradation were identified by metagenomics.