Strategies for Metabolic Engineering of Escherichia coli for β-Carotene Biosynthesis.

β-Carotene has extensive applications in the food, pharmaceutical, and cosmetics industries. Traditional chemical synthesis methods face challenges such as byproduct residues and high costs, whereas natural extraction is constrained by low yields and complex processes. Recent advancements in synthetic biology and metabolic engineering have paved the way for the heterologous biosynthesis of β-carotene in microorganisms. Owing to its rapid growth, convenience of genetic manipulation, and suitability for producing apocarotenoids, Escherichia coli is an ideal host for the production of β-carotene and its derivatives, as exemplified by the record production of multiple apocarotenoids in engineered E. coli strains. Here, we summarize the metabolic engineering strategies employed to produce β-carotene in E. coli, including manipulation of the endogenous MEP pathway, introduction of the hybrid MVA pathway, modulation of central carbon metabolism, modification of the cell membrane, and fermentation process optimization. As β-carotene acts as a biosynthetic hub for many carotenoids and apocarotenoids, we also highlighted the importance of efficient β-carotene production for the sustainable preparation of these compounds. This review aims to provide theoretical insights for designing talented β-carotene producers and laying the foundation for the sustainable manufacturing of valuable carotenoids and apocarotenoids.