Engineering Escherichia coli for high-level poly(3-hydroxybutyrate) production: Recent advances and future...

This review summarizes key progress in engineering Escherichia coli for efficient poly(3-hydroxybutyrate) (PHB) production and highlights emerging strategies that strengthen its role as a promising chassis for sustainable bioplastic production. PHB is a biodegradable polymer that has emerged as a promising alternative to petroleum-derived plastics. Owing to its biocompatibility, non-toxicity, and versatility for various applications, global interest in PHB production through fermentation has increased rapidly. Although several heterologous hosts have been engineered for PHB production, Escherichia coli has become the preferred microbial chassis due to its rapid growth, genetic accessibility, and ease of genetic manipulation. Recent progress in synthetic biology and metabolic engineering has enabled substantial improvements in PHB production by optimizing precursor availability, enhancing reducing power, and fine-tuning pathway expression. In particular, engineering glycolytic routes, introducing synthetic pathways such as the reductive glycine and threonine bypass pathways, deleting competing pathways, phasin expression, optimizing promoters, and cofactor regeneration strategies have collectively contributed to high PHB accumulation in recombinant E. coli. Overall, these advances demonstrate that engineered E. coli can serve as a robust and versatile platform for the sustainable and scalable production of PHB, supporting the growing demand for biodegradable plastics.