Microbial Production of l-Threonine Using Metabolically Engineered .

l-Threonine is one of the essential amino acids and has broad applications in food, pharmaceuticals, cosmetic products, and feed. Currently, its production depends on sustainable, environmentally friendly, and cost-effective microbial fermentation utilizing renewable carbon sources. With the global demand for l-threonine rising annually, achieving high production efficiency at economical costs has become a major focus of research. Multiple metabolic engineering approaches have been implemented to develop efficient l-threonine microbial cell factories, providing theoretical insights to support industrial-scale l-threonine production. This paper reviews systematic metabolic engineering approaches to develop l-threonine microbial cell factories, explores the application of novel tools and strategies, examines research aimed at enhancing cell robustness, and discusses fermentation condition optimization. Lastly, the challenges in constructing efficient l-threonine-producing strains are highlighted, providing theoretical insights to support industrial-scale l-threonine production.