A chemo-microbial hybrid process for the production of 2-pyrone-4,6-dicarboxylic acid as a promising bioplastic monomer from PET waste

In this study, 2-pyrone-4,6-dicarboxylic acid (PDC), a valuable monomer for bio-degradable plastic, was synthesized using terephthalic acid (TPA) derived from waste PET by a comprehensive chemo-microbial hybrid process. Depolymerization of PET into TPA was performed via microwave-assisted hydrolysis using biomass-derived SiO2 catalysts with thiol functionalization. The increased PET hydrolysis efficiency was investigated by reaction kinetics studies. The conversion of TPA obtained by depolymerization of PET waste into PDC was achieved using two recombinant Escherichia coli strains expressing tphAabc and tphB genes for TPA degradation to protocatechuic acid (PCA) through 3,4-dihydroxy-cyclohexa-1,5-diene-1,4-dicarboxylic acid (DCD) (E. coli `PCA strain) and using the ligABC genes from PCA to PDC through 4-carboxy-2-hydroxymuconate semialdehyde (CHMS) (E. coli PDCPCA strain). Using a combination of these recombinant strains, a high efficiency PDC production platform was developed using a double-catalyst system composed of the E. coli PCA strain concentrated.