Communal microaerophilic–aerobic biodegradation of Amaranth by novel NAR-2 bacterial consortium

A novel bacterial consortium, NAR-2 which consists of Citrobacter freundii A1, Enterococcus casseliflavus C1 and Enterobacter cloacae L17 was investigated for biodegradation of Amaranth azo dye under sequential microaerophilic–aerobic condition. The NAR-2 bacterial consortium with E. casseliflavus C1 as the dominant strain enhanced the decolorization process resulting in reduction of Amaranth in 30 min. Further aerobic biodegradation, which was dominated by C. freundii A1 and E. cloacae L17, allowed biotransformation of azo reduction intermediates and mineralization via metabolic pathways including benzoyl-CoA, protocatechuate, salicylate, gentisate, catechol and cinnamic acid. The presence of autoxidation products which could be metabolized to 2-oxopentenoate was elucidated. The biodegradation mechanism of Amaranth by NAR-2 bacterial consortium was predicted to follow the steps of azo reduction, deamination, desulfonation and aromatic ring cleavage. This is for the first time the comprehensive microaerophilic–aerobic biotransformation pathways of Amaranth dye intermediates by bacterial consortium are being proposed.

► Novel NAR-2 bacterial consortium could decolorize Amaranth azo dye in 30 min. ► LC–MS/MS analyses of microaerophilic–aerobic biotransformation pathways were presented. ► Microaerophilic biodegradation pathways include azo reduction, deamination and desulfonation. ► Benzoyl-CoA and protocatechuate metabolisms, as well as naphthalene degradation happened. ► Autoxidation of aromatic amine to cinnamic acid was elucidated.