Mineralization of persistent azo dye pollutants by a microaerophilic tropical lake sediment mixed bacterial consortium

Abstract

Biological degradation of azo-class industrial dye pollutants is the preferred method of remediation due to its cost effectiveness and environmentally friendly nature. These pollutants however, are known xenobiotics that resist conventional biodegradation methods. The bacterial degradation of azo-class pollutants entails a two-step anaerobic-aerobic sequential process for complete degradation. This study explored the possibility of utilization of a microaerophilic mixed bacterial consortium from tropical lake sediment to conduct a single-step complete mineralization of two azo-class dyes Methyl Orange (MO) and Congo Red (CR). Biodegradation experiments indicated decolourisation, degradation of chemical Oxygen demand (COD), biochemical Oxygen demand (BOD) removal rates in excess of 95% within 50 hours. Degradation metabolite analysis of MO and CR experiments by liquid chromatography-mass spectrometry (LC-MS) indicated that both dyes were catabolised into simpler compounds. Molecular phylogeny of several bacterial isolates from the experiments indicated that individual bacterial isolates possessed MO and CR degradation capability. Findings of this work imply that microaerophilic bacterial populations from tropical lake sediments are capable of rapid mineralisation of complex azo-class pollutants.