Advances in the Production of Theanine by Plants and Microorganisms

Theanine, a representative non-protein amino acid in tea, is one of the umami components of tea and a major factor in the formation of the unique flavor of tea leaves. In addition to its delicious taste, theanine has a variety of health functions and is used in the food supplement, pharmaceutical, nutraceutical, and cosmetic industries. This review briefly describes the physiological functions, application prospects, and production methods of theanine. The biosynthetic pathway of L-theanine in natural plants is also introduced. Finally, the microbial synthesis of L-theanine is divided into two major biosynthetic pathways guided by glutamine and glutamate according to the different substrates. According to the status, at present, of the microbial synthesis of L-theanine, the future development of microbial synthesis of L-theanine is prospected, in order to provide technical and theoretical basis for in-depth research on the industrial production of theanine.