How can L-tryptophan production in Escherichia coli be improved using biosensor-based, high-throughput screening, and metabolic engineering?

L-tryptophan (L-Trp) is an essential amino acid with increasing demand in pharmaceuticals, food, and animal feed. Traditional production methods like casein hydrolysis, enzymatic conversion, and chemical synthesis are inefficient. Microbial fermentation, especially using Escherichia coli, has become the dominant approach for industrial-scale L-Trp production. However, wild-type E. coli produces low L-Trp titers, necessitating the development of more efficient production strains through metabolic engineering.

From: "Improvement of L-Tryptophan Production in Escherichia coli Using Biosensor-Based, High-Throughput Screening and Metabolic Engineering", Fermentation 2025, 11(5), 267;

L-tryptophan production in Escherichia coli can be significantly improved by integrating biosensor-based high-throughput screening with rational metabolic engineering. The study employed atmospheric and room temperature plasma (ARTP) mutagenesis to generate a mutant library, followed by high-throughput screening using an L-Trp-specific riboswitch and a YFP-based biosensor in a flow cytometric cell sorting (FACS) system. The identified mutant strain GT3938 exhibited a 1.94-fold increase in L-Trp production. Further metabolic engineering, including knocking out the L-Trp intracellular transporter gene (tnaB), enhancing the expression of the aromatic amino acid exporter (YddG), and optimizing precursor supply pathways, led to the development of strain zh08, which achieved an L-Trp titer of 3.05 g/L, representing a 7.71-fold improvement over the original strain. This study demonstrated the effectiveness of combining biosensor-assisted screening with metabolic engineering for industrial strain development.