Biodegradation of terephthalic acid using Rhodococcus erythropolis MTCC 3951: Insights into the degradation process, applications in wastewater treatment and polyhydroxyalkanoate production.

ABSTRACT

Terephthalic acid (TPA) is an endocrine disruptor widely used as a plasticizer and as a monomer in the manufacturing of PET bottles. However, because of various harmful effects on humans and the environment, it is now recognized as a priority pollutant whose environmental level needs to be controlled. In the present work, the TPA biodegradation efficacy of the bacterium Rhodococcus erythropolis (MTCC 3951) was studied in mineral salt media with TPA as the sole carbon and energy source. R. erythropolis was observed to degrade 5 mM and 120 mM TPA within 10 h and 84 h of incubation, respectively. The degradation efficiency was further optimized by varying the culture conditions, and the following optimum conditions were obtained inoculum size- 5% (v/v), temperature- 30 °C, agitation speed- 200 rpm, and pH- 8.0. The bacterium was found to use an ortho-cleavage pathway for TPA degradation determined based on enzymatic and GC-MS studies. Moreover, during the degradation of TPA, the bacterium was observed to produce polyhydroxyalkanoate (PHA)-a biopolymer. Biodegradation of 120 mM TPA resulted in an accumulation of PHA. The PHA granules were visualized using fluorescence and transmission electron microscopy and were later characterized using FTIR spectroscopy. Furthermore, the robustness of the bacterium was demonstrated by its ability to degrade TPA in real industrial wastewater. Overall, R. erythropolis (MTCC 3951) hold the potential for controlling TPA pollution in the environment and vis-à-vis the production of PHA biopolymer.