Conventional plastic pollution poses severe threats to ecological environments and human health. As a biodegradable bioplastic, polyhydroxyalkanoate (PHA) has attracted extensive attention as an alternative to traditional petroleum-based plastics. Nevertheless, its large-scale commercial application is restricted by high production costs. Utilizing waste plastics as carbon substrates for microbial PHA biosynthesis can not only realize efficient recycling of plastic waste but also cut down PHA manufacturing expenses. Therefore, developing transformation technologies to convert waste conventional plastics into biodegradable biopolymers is of great significance for mitigating plastic pollution, advancing circular economy and achieving sustainable development.
Terephthalic acid (TPA), generated from the hydrolysis of polyethylene terephthalate (PET), exhibits great potential as a carbon source for microbial PHA synthesis. However, isolating and domesticating microbial strains that can efficiently convert TPA into PHA remains a major technical bottleneck.
The research team led by Professor Yin Wang from the Institute of Urban Environment, Chinese Academy of Sciences enriched mixed microbial consortia from sludge via shake-flask cultivation. Taking TPA—the hydrolysate of PET—as the sole carbon source, the team carried out fed-batch fermentation in a 5 L bioreactor and successfully realized the bioconversion of TPA to PHA. The maximum PHA concentration reached 2.25 g/L during fermentation, with a conversion yield of 0.10 g PHA per gram of TPA.
Through gene annotation and identification of intermediate metabolites, the research clarified the composition of dominant microbial populations and the metabolic pathways of TPA transformation. The results verified remarkable synergistic effects within the microbial consortium: different strains secrete specific enzymes to sequentially convert TPA into protocatechuic acid or catechol, which are ultimately transformed into acetyl-CoA—the key precursor for PHA biosynthesis.
This study establishes a sustainable technical route for the high-value upcycling of waste PET into biodegradable polymers. The metabolic mechanisms revealed in this work provide critical theoretical support for boosting PHA production efficiency in future research.
