Visible Light-induced Formic Acid Synthesis from HCO3− with Formate Dehydrogenase and Water-soluble Zinc Porphyrin

Photochemical and enzymatic synthesis of formic acid was investigated from HCO3− with formate dehydrogenase (FDH) from Saccharomyces cerevisiae and reduced methylviologen (MV2+) produced by the visible light photosensitization of zinc tetrakis(4-methylpyridyl) porphyrin (ZnTMPyP) in the presence of triethanolamine (TEOA) as an electron donating reagent. Irradiation of a solution containing TEOA, ZnTMPyP, MV2+, NaHCO3 and FDH in potassium phosphate buffer, with visible light resulted in formic acid production and HCO3− consumption. The optimum FDH activity was 20 units and the amount of formic acid and the yield of HCO3− to formic acid after 4 h irradiation were estimated to be 50 μmol·dm−3 and 5.0%, respectively.