From Tea Leaves to Factories: A Review of Research Progress in l-Theanine Biosynthesis and Production

Abstract

l-Theanine is the most popular nonprotein amino acid contained in tea leaves. It is one of the umami components of green tea, contributing to the unique flavor of tea. Because of its various health functions, l-theanine has been commercially developed as a valuable ingredient easily used for various applications in food and pharmaceutical industries. Nowadays, l-theanine is mass-produced by plant extraction, chemical synthesis, or enzymatic transformation in factories. This review embodies the available up to date information on the l-theanine synthesis metabolism in the tea plant as well as approaches to produce it, placing emphasis on the biotransformation of l-theanine. It also gives insight into the challenges of l-theanine production on a large scale, as well as directions for future research. This review comprehensively summarizes information on l-theanine to provide an approach for an in-depth study of l-theanine production.

l-Theanine Inhibits (−)-Epigallocatechin-3-gallate Oxidation via Chelating Copper

“…To examine this possibility, mice were randomly divided into two groups ( n = 6/group) and were administered with EGCG or EGCG plus l -theanine once daily for 3 consecutive days. l -Theanine and EGCG account for 0.7–4 and 4–8% of the dry weight of green tea, respectively. , The mass ratio of l -theanine to EGCG therefore could be 1:10 to 1:2 in green tea depending upon tea varieties and the conditions of cultivation and processing. Therefore, 55 mg/kg EGCG and 13 mg/kg l -theanine were employed (the mass ratio of l -theanine to EGCG is roughly 1:4).…”

“…L-Theanine and EGCG account for 0.7−4 and 4−8% of the dry weight of green tea, respectively. 1,33 The mass ratio of L-theanine to EGCG therefore could be 1:10 to 1:2 in green tea depending upon tea varieties and the conditions of cultivation and processing. Therefore, 55 mg/kg EGCG and 13 mg/kg L-theanine were employed (the mass ratio of L-theanine to EGCG is roughly 1:4).…”

Sensory and chemical characteristics of Tieguanyin oolong tea after roasting

“…Amino acids have positive influences on tea infusion taste. l -theanine can relieve the bitterness and astringency, and enhance the umami and sweetness taste ( Chen, Wang, Yuan, & He, 2021 ). l -glutamic acid can increase the umami taste ( Zhang, Sun-Waterhouse, Su, & Zhao, 2019 ).…”

United States tea: A synopsis of ongoing tea research and solutions to United States tea production issues

“…The biosynthesis of L-theanine in tea begins with the amino acid L-glutamate (Figure 2C; Chen et al, 2021). It is known that mature plants are the highest producers of L-theanine, with the biosynthetic pathway being the most active in the roots.…”