Microbial synthesis and degradation of bio-based biodegradable plastics.

Microorganisms facilitate both the synthesis and breakdown of bio-based biodegradable plastics, which positions them as central players in the development of a future circular plastics economy. However, advances in microbial production and biodegradation of plastics are often considered in isolation, limiting our ability to integrate these processes into viable circular systems. In this Review, we discuss the contributions of microorganisms across the life cycle of key bio-based polymers, focusing on polyhydroxyalkanoates, bacterial nanocellulose, and the monomers of polylactic acid and polyethylene furanoate, and we critically assess the extent to which current microbial capabilities can support polymer synthesis and degradation. Although the genetic capacity for these processes is widespread, this does not necessarily translate into efficient synthesis or biodegradation in industrial or environmental conditions. Microbial synthesis remains constrained by low volumetric productivity, carbon inefficiencies and downstream processing challenges, whereas biodegradation is highly dependent on material properties and environmental conditions, with efficient biodegradation often limited to managed settings. Thus, achieving an effective circular bio-based plastic economy requires the integration of microbial engineering, polymer chemistry, material science and other disciplines to optimize both production and end-of-life management.