Systems metabolic engineering and process optimization for efficient l-tyrosine production from high-purity glucose syrup in Escherichia coli

Abstract

l-tyrosine (l-tyr) is a valuable aromatic amino acid that can be produced via microbial fermentation, providing a sustainable alternative to costly and polluting chemical synthesis. However, industrial production is limited by poor strain performance and inefficient resource utilization. In this study, a high-performance Escherichia coli strain was engineered to address key fermentation bottlenecks for efficient l-tyr synthesis from high-purity glucose syrup. Initially, a “rapid channel” for l-tyr biosynthesis was established by overexpressing aroG^fbr and tyrA^fbr genes, introducing the pyridoxal 5’-phosphate synthesis pathway, and strengthening tyrosine efflux. Precursor pools of phosphoenolpyruvate and erythrose-4-phosphate were enriched using modular metabolic engineering and dynamic regulation strategies. Co-metabolism of glucose, maltose, and isomaltose was achieved by integrating Bacillus subtilis-derived membrane permease and maltose-6’-phosphate glucosidase, alongside Bifidobacterium adolescentis-derived oligo-1,6-glucosidase, and by employing a suboptimal glucose supplementation feeding strategy. To overcome oxygen limitation, Vitreoscilla hemoglobin was localized to the periplasm via the twin-arginine translocation pathway. Systematic fermentation optimization further improved strain performance, achieving an l-tyr titer, yield, and productivity of 109.2 g/L, 0.292 g/g, and 2.18 g/L/h, respectively—the highest reported to date. This research demonstrates a promising strategy for enhancing l-tyrosine biosynthesis, providing a scalable approach for industrial production and broader applications in microbial metabolic engineering.