Fuente: PubMed "microbial biotechnology" Bioresour Technol. 2026 May 29:135025. doi: 10.1016/j.biortech.2026.135025. Online ahead of print.ABSTRACTl-Tryptophan (l-Trp), an essential amino acid for humans and animals, is extensively used in the pharmaceutical, food, and feed industries. In order to further increase the production efficiency of l-Trp in E. coli, the metabolic bottlenecks (phosphoenolpyruvate, shikimate, l-Glutamine, and l-Serine) were identified by integrating intracellular metabolite profiling and transcriptional analysis. Among them, the intracellular level and molar ratio of l-Glutamine (l-Gln) and l-Serine (l-Ser) were found to affect cell growth and l-Trp production. When the ratio was controlled at 5.0:4.0, the titer of l-Trp could increase by 18.6%. To dynamically maintain this ratio, a regulatory system termed RNAi-SG was constructed by integrating the l-Gln-responsive transcriptional repressor (GINLB) with RNA interference. This system could enhance repression strength by 43.3% and maintain the intracellular l-Gln:l-Ser ratio near 5.0:4.0 during 6-42 h fermentation. When implemented in strain TRPA, RNAi-SG* increased l-Trp titer and yield to 68.2 g/L and 0.260 g/g after 52 h fermentation. This study establishes a dynamic precursor ratio control strategy that synchronizes l-Gln and l-Ser supply, providing a real-time manipulation system to control precursors supply for microbial cell factories during fermentation.PMID:42217805 | DOI:10.1016/j.biortech.2026.135025