Community Synergism: Degradation of Triazine Dye Reactive Black 1 by Mixed Bacterial Cultures KND_PR under Microaerophilic and Aerobic Conditions

Abstract

Mixed bacterial cultures KND_PR comprising five bacterial species, namely Lysinibacillus sp. BAB-4931, Raoultella sp. BAB-4932, Enterococcus sp. BAB-4933, Citrobacter sp. BAB-4934 and Lysinibacillus sp. BAB-4935, were originally developed from contaminated soil near Pirana, Ahmedabad, India. KND_PR have an astonishing ability to degrade Reactive Black 1 (RB1) under both microaerophilic and aerobic conditions within 8 and 12 h, respectively. Mixed bacterial cultures KND_PR showed azoaromatic degradation efficiency up to 1500 mg/L of dye concentration and were able to tolerate salt up to 25 g/L. KND_PR can degrade twenty-five structurally different complex dyes that indicate its catabolic versatility. During azoaromatic degradation, it was observed that under microaerophilic condition KND_PR first followed symmetric cleavage of the azo bond by azoreductase, whereas, under aerobic condition, asymmetric cleavage of RB1 took place via lignin peroxidase. Metabolic pathways for RB1 degradation by KND_PR has been postulated with enzymatic and bioanalytical techniques, which showed the significant conversion of parent dye into low molecular weight aliphatic compound. These results were further confirmed by observing significant results of phytotoxicity experiments with model plants under microaerophilic and aerobic conditions. The foregoing results indicate that the enriched mixed bacterial cultures can efficiently degrade dye under microaerophilic and aerobic conditions within a short time period, which exhibited the usefulness of mixed bacterial cultures KND_PR to tackle the problems associated with dye contaminated wastewater.