Production of L-Theanine by Escherichia coli in the Absence of Supplemental Ethylamine

L-Theanine is a nonproteinogenic amino acid present almost exclusively in tea plants and is beneficial for human health. For industrial production, L-theanine is enzymatically or chemically synthesized from glutamine/glutamate (or a glutamine/glutamate derivative) and ethylamine. Ethylamine is extremely flammable and toxic, which complicates and increases the cost of operational procedures. To solve these problems, we developed an artificial biosynthetic pathway to produce L-theanine in the absence of supplemental ethylamine. For this purpose, we identified and selected a novel transaminase (NCBI:protein accession number AAN70747) from Pseudomonas putida KT2440, which catalyzes the transamination of acetaldehyde to produce ethylamine, as well as gamma-glutamylmethylamide synthetase (NCBI:protein accession number AAY37316) from Pseudomonas syringae pv. syringae B728a, which catalyzes the condensation of L-glutamate and ethylamine to produce L-theanine. Expressing these genes in Escherichia coli W3110S3GK and enhancing the production capacity of acetaldehyde and L-alanine achieved successful production of L-theanine without ethylamine supplementation. Furthermore, the deletion of ggi, which encodes gamma-glutamyltranspeptidase (EC 2.3.2.2), achieved large-scale production of L-theanine by attenuating its decomposition. We show that an alanine decarboxylase-utilizing pathway represents a promising route for the fermentative production of L-theanine. Our study reports efficient methods to produce L-theanine in the absence of supplemental ethylamine. IMPORTANCE L-Theanine is widely used in food additives and dietary supplements. Industrial production of L-theanine uses the toxic and highly flammable precursor ethylamine, raising production costs. In this study, we used Escherichia coli to engineer two biosynthetic pathways that produce L-theanine from glucose and ammonia in the absence of supplemental ethylamine. This study establishes a foundation for safely and economically producing L-theanine.

Automated summary

The study presents an efficient method for producing L-theanine without supplemental ethylamine, using engineered biosynthetic pathways in Escherichia coli. By optimizing gene expression and enhancing production capacity, successful large-scale production of L-theanine was achieved, laying the foundation for safe and economical production of this beneficial compound.