RESUMO
The ability of hydrogenases isolated from Thiocapsa roseopersicina and Lamprobacter modestohalophilus to reduce metal ions and oxidize metals has been studied. Hydrogenases from both phototrophic bacteria oxidized metallic Fe, Cd, Zn and Ni into their ionic forms with simultaneous evolution of molecular hydrogen. The metal oxidation rate decreased in the series Zn > Fe > Cd > Ni and depended on the pH. The presence of methyl viologen in the reaction system accelerated this process. T. roseopersicina and L. modestohalophilus cells and their hydrogenases reduced Ni(II), Pt(IV), Pd(II) or Ru(III) to their metallic forms under H2 atmosphere. These results suggest that metals or metal ions can serve as electron donors or acceptors for hydrogenases from phototrophic bacteria.
Assuntos
Chromatiaceae/enzimologia , Hidrogenase/metabolismo , Metais Pesados/metabolismo , Thiocapsa roseopersicina/enzimologia , Chromatiaceae/ultraestrutura , Hidrogênio/metabolismo , Microscopia Eletrônica de Transmissão , Oxirredução , Thiocapsa roseopersicina/ultraestruturaRESUMO
Hydrogenases encapsulated in porous polymeric silica gels retain significant levels of hydrogen production activity when compared to hydrogenases in solution using reduced methyl viologen as an electron donor. Encapsulated hydrogenases remain active after storage at room temperature for longer than four weeks and are less sensitive to proteolytic digestion. Nanoscopic confinement of active hydrogenases in solids paves the way for their potential use in hydrogen producing catalytic materials applications.
