Nanoparticle-tethered NAD+ with in situ cofactor regeneration

A new and simple route for the preparation of immobilized NAD⁺ on carboxyl-activated silica nanoparticles activated by γ-aminpropyltriethoxysilane and glutaric anhydride was developed. In addition, formate dehydrogenase, keto-reductase and the silica nanoparticle-attached NAD⁺ were applied to catalyze the coupled reactions for production of l-lactate with the cofactor regenerated within the reaction cycle. As indicated by thermogravimetric analysis and FT-IR, the silica nanoparticles were successfully activated and the loading of carboxyl groups was 0.53 mmol g^?1 particle. The amount of immobilized NAD⁺ on the support was 73 mg g^?1 particle. With 0.2 M pyruvate and 3 M formate, 0.16 M l-lactate was produced after the coupled reactions. The immobilized system showed excellent efficiency and stabilities in recycling, and it retained 60 % residual activity even after six reuses.