Advancing plastics bio-upcycling with photosynthetic microorganisms using bioengineering and bioconversion strategies

Biotechnological interventions have been increasingly adopted for addressing the persistence and recalcitrance of fossil fuel-derived plastic waste. Bioremediation through microbial and enzymatic degradation offers promising solutions, yet economic and scalability challenges persist, especially for addressing plastic waste accumulation in aquatic ecosystems. Despite recent advancements in plastic bioconversion and bio-upcycling using recombinant enzymes and microbes, current genetic and biological engineering platforms mainly employed heterotrophic chassis such as Escherichia coli and Pseudomonas putida, that are not suitable for direct cultivation using wastewater sources. Photosynthetic microorganisms like cyanobacteria and microalgae offer a sustainable alternative to the heterotrophic counterparts, in not only converting wastewater and CO₂ as carbon and energy sources but also bring about carbon-neutral bioconversion potentials. Therefore, this review explores bioengineering strategies required to develop and harness the capabilities of cyanobacteria and microalgae for plastic biomineralisation. Pathway engineering in selected chassis is highlighted by detailing the metabolic pathways involved in plastic degradation where the application of growth-coupled genome editing and advanced biotechnological tools is further discussed. By integrating biofoundry-driven bioengineering strategies with growth-coupled selection, microalgal strain development can be accelerated towards achieving high substrate-to-product yields thus promoting carbon-neutral biorefinery and plastic bioconversion approaches.