Biological Degradation of Phthalates: From Bioremediation to Plastic Waste Valorization

Terephthalic, ortho-phthalic, and isophthalic acid (i.e., phthalates) are aromatic petrochemicals with an important role in the plastics industry, since they are precursors for both polymers and plasticizers. Although their large-scale industrial production is less than 80 years old, the recalcitrance and accumulation of plastics and plasticizers in the environment have caused severe pollution and health concerns. In this context, the biodegradation of these xenobiotic compounds and derived products has gained significant attention in recent years, as it could provide environmentally-friendly solutions for the removal of these contaminants from the environment and for the biological recycling and valorization of phthalate-derived plastic waste. Here, we review the known microbial mechanisms for the degradation of the three phthalate isomers and derived esters (polymers and plasticizers), focusing on bacterial hydrolases and catabolic pathways for the assimilation of the aromatic monomers. We then highlight recent advances made in the bioremediation of phthalates in the environment, the engineering of more efficient enzymes for the recycling of polymers and the degradation of plasticizers, the development of microbial cell factories for the valorization of phthalates, and the application of new biosensor tools. In all, this review highlights the potential of microbial biotechnology in achieving a circular economy for plastics.