Recent Advances, Challenges, and Metabolic Engineering Strategies in L-Cysteine Biosynthesis

L-Cysteine is a widely used unique sulfur-containing amino acid with wide application in the food, pharmaceutical, and agricultural industries. This paper concludes the advantages and disadvantages of chemical hydrolysis, enzymatic biotransformation, and fermentation for the synthesis of L-cysteine. Meanwhile, a detailed introduction is given to the biosynthesis of L-cysteine, metabolic engineering strategies, and the latest progress in reported L-cysteine fermentation bacteria. Finally, insights are provided on the development direction of increasing the production of biosynthetic L-cysteine in the future. This review provides ideas for the future development of more efficient L-cysteine biosynthetic pathways.