Hydrogen Evolution with Hydrogenase by Using Ammonium Salts as Electron Carriers

Abstract

Various dye staffs have been used as electron carriers to evolve hydrogen with hydrogenase. Viologen dyes such as ethyl- and propylviologens were found to be suitable electron carriers. Among viologen dyes propylviologen was most effective for hydrogen evolution. Kinetic studies have been carried out by using Safranine T and Neutral Red as electron carriers. In the case of Safranine T system, the hydrogen evolution rate was expressed by equation;
ν=D[H₂]/dt=k₁²[s]²/(1+K₁[s])²
where [S] is the concentration of Safranine T, and k and K₁ are rate constant and equilibrium constant, respectively. On the basis of the above equation, the reaction mechanism is proposed. The hydrogen evolution rate decreased with reaction time. It may be caused by the deactivation of Safranine T itself. When Neutral Red was used as an electron carrier, the turnover number of hydrogen evolution against Neutral Red was 15.2 after 3 h reaction. In this case the hydrogen evolution rate also decreased with reaction time. The inhibition of hydrogenase activity by dimerization of reduced form of Neutral Red or by decrease of the concentration of the leuco form may be responsible for the rate decrease.