Regeneration of NAD + cofactor by photosensitized electron transfer in an immobilized alcohol dehydrogenase system

The irradiation with visible light of a photosensitizer dye like methylene blue was used to regenerate by electron transfer the oxidized form of a pyridine nucleotide coenzyme (NAD + ). The process has been studied on a common enzymatic reaction: ethanol oxidation by alcohol–NAD + oxidoreductase immobilized on polyacrylamide gel or porous glass balls. In the experimental conditions used, the initial NAD + recycling rates were 2.33 × 10 4 cycles/h (polyacrylamide) and 3 × 10 4 cycles/h (glass balls). A total number of 49.5 × 10 4 cycles was obtained for 13 runs of 2 h. The enzyme immobilization strongly increased its stability: after 28 days at 20°C, the residual activity was 25% of the initial value.