Establishing biosynthetic pathways for the production of nicotinic acid and trigonelline in Escherichia coli.

Microbial cell factories offer a sustainable platform for the production of natural products, but their development is often constrained by inefficient or poorly characterized native biosynthetic pathways. Nicotinic acid (NA) and its N-methylated derivative trigonelline (TG) are valuable compounds with broad applications in pharmaceuticals, nutraceuticals, and the chemical industry. In this study, we present a novel strategy for the de novo biosynthesis of NA and TG from glucose using engineered Escherichia coli strains. By systematically analyzing and redesigning biosynthetic routes, we constructed an artificial pathway for NA synthesis, significantly reducing energy and cofactor requirements. We optimized the supply of key precursors, including quinolinic acid (QA) and 5-phosphoribosyl-1-pyrophosphate (PRPP), and eliminated competing metabolic routes, resulting in a NA titer of 1.19 g/L in a 3-L fermenter, representing a 200-fold improvement over the original strain. We also extended the pathway to produce TG by screening and introducing the NA N-methyltransferase CTgS1, achieving the first reported de novo production of TG from glucose, with a titer of 153.3 mg/L. This work highlights the potential of rationally designed, heterologous biosynthetic pathways for the efficient production of natural products and their derivatives, providing a foundation for further optimization and large-scale industrial application.