Valorization of polyester wastes into polyhydroxyalkanoates via a one-step microbial fermentation process

Polyhydroxyalkanoates (PHAs) are promising biodegradable alternatives to petroleum-based plastics, yet their large-scale application remains hindered by high production costs. Here, a direct and cost-effective microbial strategy to upcycle polyester waste into PHAs using Paracoccus denitrificans was investigated. Remarkably, the bacterium metabolized 10 out of 12 tested plastic-derived monomers and efficiently accumulated intracellular PHAs, even when fed with pretreated mixed polyester waste instead of purified substrates. More than 80% of polyester monomers supported growth, and medium optimization through nitrogen reduction boosted PHA content up to 30% of cell dry weight. This one-step process circumvents costly separation steps, enabling the valorization of heterogeneous plastic mixtures and significantly reducing both economic and processing burdens. By transforming post-consumer plastics into high-value biopolymers, this work positions P. denitrificans as a versatile platform for circular bioeconomy strategies, directly supporting global sustainability agendas and advancing sustainable bioprocessing for the green industry.