Niacin, also known as nicotinic acid or vitamin B3, together with nicotinamide constitutes vitamin PP, the anti-pellagra factor, and is one of the essential nutrients required by the human body. As a common vitamin-based drug, nicotinic acid has wide applications spanning the pharmaceutical, food and chemical industries and also serves as a widely used feed additive; it can help regulate blood lipid levels and protect the cardiovascular and cerebrovascular systems. Traditional industrial production relies on chemical synthesis, which typically requires high temperatures, high pressures and strong acid or alkali conditions, and generates large amounts of waste salts that must be neutralized. Biocatalysis using nitrilase is a cleaner route, but the poor operational stability of free enzymes and the difficulty of recovering them have limited practical application.
Corynebacterium glutamicum is a Generally Recognized as Safe (GRAS) Gram-positive bacterium with a highly permeable cell wall, no endotoxin, high protein secretion capacity, well-defined metabolic pathways and suitability for high-density cultivation, making it an ideal host for whole-cell biocatalysis. A team led at Jiangnan University engineered C. glutamicum to express a mutant nitrilase from Pseudomonas putida and then encapsulated the whole cells in a biomimetic hybrid shell. The core-shell architecture, comprising a zeolite core, PEG200 crosslinking and a silica shell derived from tetraethyl orthosilicate (TEOS), was designed to balance the mechanical robustness provided by the silica shell against the biocompatibility and mass transfer afforded by PEG200 crosslinking.
Systematic optimization of the immobilization conditions, at 6 g/L zeolite, 50 g/L cell loading, 3 g/L PEG200 and 7 g/L TEOS, yielded a molar conversion rate of 88.78% for 50 g/L 3-cyanopyridine, significantly outperforming free cells at 62.83%. Scanning electron microscopy confirmed the formation of a dense yet porous core-shell structure. Compared with free cells, the immobilized biocatalyst exhibited optimal activity at 40 °C and pH 7.0, with a broader pH tolerance range of 7.0 to 9.0.
The decisive advantage emerged in repeated batch reactions: the immobilized cells achieved 14 reuse cycles at a loading of 700 g/L, producing 603.56 g/L nicotinic acid at a total molar conversion of 90.2%, whereas free cells were limited to 12 cycles and 86.7% conversion. This work establishes a sustainable biocatalytic platform for nicotinic acid production and demonstrates a generalizable immobilization strategy for whole-cell catalysis based on rationally designed organic-inorganic hybrid shells. The authors note that systematic studies on PEG200 recovery, ethanol emission control and regeneration of spent carriers have not yet been performed, and that future work will include a full life-cycle assessment to quantitatively compare the environmental footprint of this biocatalytic route with that of conventional chemical processes.
The work entitled “Efficient synthesis of nicotinic acid by biomimetic mineralization-immobilized whole-cell biocatalysts” was published in Systems Microbiology and Biomanufacturing (published on Sep. 4, 2026).
DOI：10.1007/s43393-026-00543-8