Abstract
An efficient bacterial consortium (designated BPA-1), comprising Bacillus subtilis SX-6, Pseudomonas sp. SX-10, and Georgenia sp. SY-1, was successfully constructed for the decolorization of the azo dye Congo Red (CR). BPA-1 exhibited significant thermotolerance and heavy metal resistance, achieving over 90% CR decolorization within 60 h at 47°C under co-stress conditions with Zn²⁺, Mn²⁺, and Pb²⁺ (50 mg/L each). The consortium demonstrated broad substrate specificity, effectively decolorizing 12 structurally diverse azo dyes. Enzymatic assays revealed the involvement of laccase, manganese peroxidase, lignin peroxidase, and azoreductase in CR biodegradation. Metabolic pathway analysis indicated a three-stage degradation mechanism: (1) Asymmetric cleavage of azo bonds (-N=N-) generated 4,4'-diazaldenylbiphenyl and 4-amino-1-naphthalenesulfonic acid (Intermediate II); (2) Deamination converted Intermediate II to 3,4-dihydroxy-1-naphthalenesulfonic acid, followed by desulfurization to form naphthalene-1,2,3,4-tetraol; (3) Complete mineralization of intermediates occurred through subsequent oxidative steps. Notably, 4,4'-diazaldenylbiphenyl was further transformed into 4,4'-diaminobiphenyl, confirming the consortium’s capacity for multi-step detoxification.
