Metabolic pathway and role of individual species in the bacterial consortium for biodegradation of azo dye: A biocalorimetric investigation

Abstract

In this study, an attempt was made to investigate the functional role and metabolic behaviour of the monoculture (Staphylococcus lentus (SL), Bacillus flexus (BF) and Pseudomonas aeruginosa (PA)) in the bacterial biocenosis for biotransformation of an azo dye. The power-time profile obtained from consortia depicted three distinct peaks, which correlated well with the individual bacterial growth (PA > SL > BF), indicating the synergistic relation and division of labour in the biocenosis. The heat release pattern was used to identify the sequential behaviour of microbial consortia in real time. Yield calculation based on total heat liberated to the complete substrate utilization Y (Q/S) for PA, SL, and BF were 15.99, 16.68, 7.32 kJ/L respectively. Similarly, the oxy calorific values Y (Q/O) for the above species are respectively 386, 375, 440 kJ/mol and indicates the aerobic nature of microorganism employed. Further, the metabolome produced during the biotransformation were identified using Gas Chromatography-Mass Spectrometry (GC-MS), based on which a plausible pathway was predicted. The abundant metabolites were palmitic acid (m/z = 256) and diethyl phthalate (m/z = 222.2). The abundance of diethyl phthalate was much lesser in the consortia compared to the monoculture. Thus, the biocalorimetric heat yield calculation along with the stoichiometry and plausible pathway based biochemical elucidation provides a mechanistic basis for understanding the azo-dye biotransformation by the monocultures in consortia.