Nicotinic acid production from 3-methylpyridine by E. coli whole-cell biocatalyst.

Nicotinic acid, a bioactive form of niacin (vitamin B3), is an essential nutrient involved in various metabolic pathways. Its deficiency can lead to severe health issues, emphasizing the need for effective production methods. Traditional chemical methods for synthesizing nicotinic acid often require harsh reaction conditions and produce environmentally hazardous byproducts. This has prompted increasing interest in more sustainable biocatalytic alternatives. In this study, we investigated the bioconversion of 3-methylpyridine (3-MP) to nicotinic acid using resting cells of recombinant Escherichia coli expressing enzymes from Pseudomonas putida mt-2. Through systematic optimization, E. coli MG1655 RARE cells co-overexpressing xylene monooxygenase (XMO: XylM and its reductase XylA) and benzyl alcohol dehydrogenase (XylB) achieved efficient biotransformation of 9 mM 3-MP to 8.28 ± 0.35 mM nicotinic acid within 12 hours, corresponding to a yield of 92.0 % ± 3.9 %. This work presents a streamlined biocatalytic route for nicotinic acid synthesis and offers a foundation for further metabolic engineering of microbial production systems.