Improvement of hydrogen productivity by introduction of NADH regeneration pathway in Clostridium paraputrificum.

To improve the hydrogen productivity and examine the hydrogen evolution mechanism of Clostridium paraputrificum, roles of formate in hydrogen evolution and effects of introducing formate-originated NADH regeneration were explored. The formate-decomposing pathway for hydrogen production was verified to exist in C. paraputrificum. Then NAD(+)-dependent formate dehydrogenase FDH1 gene (fdh1) from Candida boidinii was overexpressed, which regenerate more NADH from formate to form hydrogen by NADH-mediated pathway. With fdh1 overexpression, the hydrogen yield via NADH-involving pathway increased by at least 59 % compared with the control. Accompanied by the change of hydrogen metabolism, the whole cellular metabolism was redistributed greatly.