Enhanced degradation of polyethylene terephthalate by a two-strain microbial consortium

Polyethylene terephthalate (PET) degradation is often limited by insufficient polymer depolymerization and the downstream conversion of hydrolysis products. In this study, Burkholderia cepacia ZY1 and Pseudomonas harudinis G1B were compared, and a two-strain consortium, YB2, was constructed at an optimal inoculation ratio of 4:5. ZY1 showed relatively stronger PET depolymerization-related activity, whereas G1B exhibited greater growth in bis(2-hydroxyethyl) terephthalate (BHET)- and mono(2-hydroxyethyl) terephthalate (MHET)-containing media and a trend toward faster BHET conversion. The hydrolytic activities of both strains were mainly cell associated, and both remained culturable, with stable relative proportions during 0-7 d of cocultivation. At pH 7.0 and 30 °C, YB2 achieved 4.30% ± 0.11% PET film mass loss after 3 d, significantly exceeding the individual strains. YB2 treatment caused surface erosion, ester-related structural changes, and increased residual PET crystallinity. The detection of BHET, MHET, and terephthalic acid (TPA) further supported PET depolymerization, while the release of ethylene glycol (EG) was also observed. YB2 converted 96.4% of BHET and 97.3% of MHET within 2 d and almost completely utilized TPA within 5 d. EG initially accumulated and then declined, suggesting possible subsequent microbial utilization. Overall, ZY1 and G1B exhibited overlapping functions with relative functional differences and potential complementarity, supporting the use of synthetic microbial consortia to enhance PET depolymerization and downstream product conversion.