Advances in microbial strain selection and carbon source valorization for Polyhydroxyalkanoates (PHA) production

Polyhydroxyalkanoates (PHAs) are biodegradable polymers produced by various microorganisms as intracellular carbon and energy reserves. Their potential to replace petroleum-based plastics has made them central to sustainable materials research. However, their large-scale commercialization is hindered by high production costs, prompting efforts to improve yield and identify low-cost, non-food carbon sources. This review examines PHA biosynthesis optimization via advances in microbial strain-substrate selection ensuring economic feasibility. Focus is placed on three key bacterial genera, Cupriavidus, Pseudomonas, and Escherichia coli analyzing their metabolic flexibility, suitable substrate range and PHA content (g product/ g substrate). Escherichia coli species and Cupriavidus necator demonstrate high polymer contents from largely simple sugars and fatty-acid substrates respectively, while Pseudomonas species offer a broad substrate adaptability, particularly waste streams. The environmental impact assessment of some Cupriavidus necator and Pseudomonas strains highlight low carbon footprint from waste lipids compared to PHA production from glucose or bottle-grade PET, however these results are contingent to specific scenarios without a reproducible and quantifiable GWP values across these genera. Integrating microbial engineering of agro-industrial and organic wastes in adherence to regulatory frameworks around waste valorization and optimization, genus-specific LCA bioprocessing approach offers a path toward economically viable and environmentally sustainable PHA production.