Advances in Metabolic Engineering of Microbial Cell Factories for the Biosynthesis of l-Serine

l-Serine, a nonessential amino acid in humans, possesses significant physiological functions and is widely used in the food, cosmetic, and pharmaceutical industries. Driven by steadily growing market demand and promising prospects, increasing attention has focused on the sustainable, biobased production of l-serine via low-carbon microbial synthesis, facilitated by advances in biotechnology. Significant progress has been made in the metabolic engineering of microbial cell factories for the biosynthesis of l-serine. This article first outlines the functions, applications, production methods, and biosynthetic pathways of l-serine across various microorganisms. Subsequently, it explores strategies for enhancing l-serine biosynthesis in engineered strains, including augmenting precursor supply, repressing competitive metabolic pathways, transporter engineering, microbial mutagenesis and breeding methods, and cofactor engineering to boost l-serine yield. Finally, considering recent developments, existing challenges, and emerging trends in the field, we discuss promising directions for future research aimed at further increasing l-serine production efficiency.