A new study on revolutionising PHA production by decoupling it from nutrient limitation

A new study, supported by the PROMICON project, uses a model-driven approach to upcycling recalcitrant feedstocks in Pseudomonas putida by decoupling PHA production from nutrient limitation. 

Bacterial polyhydroxyalkanoates (PHAs) provide an eco-friendly alternative to petroleum-based plastics, synthesised from renewable resources and offering excellent material properties. However, their production is traditionally limited to the stationary growth phase under nutrient-limited conditions, requiring complex and costly two-phase bioprocesses. During the first phase, the bacteria are provided with an abundant supply of nutrients, particularly carbon, to allow them to multiply and accumulate biomass. This phase ensures that a substantial population of bacteria is available for the subsequent production phase. Once the desired cell density is achieved, the second production phase begins by limiting the availability of certain nutrients, particularly nitrogen, while still maintaining sufficient levels of other nutrients necessary for PHA synthesis. While the two-step bioprocess effectively produces PHA, it comes with important challenges including the need for separate growth and production phases, which results in energy-intensive and resource-consuming processes. 

 Workflow used in this study

The research employs synthetic biology and growth-coupling strategies to reroute carbon flux, allowing PHA production during the growth phase. This approach led to the production of up to 46% PHA per cell dry weight while maintaining a balanced carbon-to-nitrogen ratio. The modified strains were further validated by using enzymatically hydrolyсed polyethylene terephthalate (PET) as a feedstock, demonstrating their ability to upcycle challenging plastic waste materials.

These findings provide a potential solution for simplifying PHA production processes, with significant implications for sustainable plastic alternatives. By removing the need for nutrient-limited conditions, this research could help reduce the costs and complexities traditionally associated with PHA production.

Recalcitrant feedstock revalorization