Microbial valorisation of PET-derived terephthalic acid by Rhizopus arrhizus: towards plastic waste biotransformation

Terephthalic acid (TPA), one of the two monomeric building blocks of polyethylene terephthalate (PET), is a recalcitrant aromatic compound commonly present in industrial waste streams. Understanding its biodegradation pathways in fungi is essential for developing effective bioremediation strategies. In this study, we report for the first time the capacity of Rhizopusarrhizus to metabolise TPA and utilise TPA as a carbon source. A reverse isotope-labelling approach combined with gas chromatography-mass spectrometry was employed to trace the metabolic fate of TPA through central carbon metabolism. Our results demonstrate rapid and complete consumption of TPA by R. arrhizus PR1 within 24-48 h. TPA-derived carbon atoms were efficiently incorporated into the tricarboxylic acid (TCA) cycle and subsequently distributed into various biosynthetic pathways, including amino acid and lipid biosynthesis. Furthermore, exposure to TPA induced a metabolic shift from fermentation to a respiro-fermentative state, as evidenced by increased TCA cycle activity and upregulation of mitochondrial pyruvate transport systems. The concomitant production of industrially relevant organic acids, such as lactic acid and fumaric acid from TPA highlights this fungi's potential for innovative biotechnological applications aimed at plastic waste valorisation and the advancement of a circular bioeconomy.