Metabolic rewiring and biosensor-assisted screening for high-level putrescine production from xylose in Escherichia...

Lignocellulosic biomass represents an abundant and renewable feedstock for sustainable biomanufacturing, with its major constituent xylose offering a cost-effective carbon source for producing value-added chemicals. Putrescine is an important platform compound with broad industrial applications, yet its conventional biosynthesis from glucose suffers from lengthy pathways, low carbon conversion efficiency, and a narrow substrate spectrum. To circumvent these thermodynamic and carbon conservation challenges, we established a synthetic putrescine biosynthesis pathway in Escherichia coli based on non-phosphorylative xylose metabolism. This streamlined route enables de novo putrescine synthesis in only 12 enzymatic steps, effectively reducing intermediate side reactions and carbon diversion, and offering higher theoretical carbon source conversion efficiency and yield. Through systematic modular optimization of the putrescine biosynthetic network, and biosensor-assisted screening, we developed a microbial platform that achieved 3.10 g/L putrescine in shake-flask cultures, representing a 484.4-fold improvement over the initial strain. In 5 L fed-batch fermentation, the putrescine titer reached 34.77 ± 1.06 g/L with a yield of 0.26 g/g xylose, demonstrating the industrial potential of this synthetic pathway. This work broadens the substrate spectrum for putrescine biosynthesis and provides a new direction for the value-added utilization of lignocellulosic biomass.