Involvement of hydrogenases in the formation of highly catalytic Pd(0) nanoparticles by bioreduction of Pd(II) using Escherichia coli mutant strains

Abstract

Escherichia coli produces at least three [NiFe] hydrogenases (Hyd-1, Hyd-2 and Hyd-3). Hyd-1 and Hyd-2 are membrane-bound respiratory isoenzymes with their catalytic subunits exposed to the periplasmic side of the membrane. Hyd-3 is part of the cytoplasmically oriented formate hydrogenlyase complex. In this work the involvement of each of these hydrogenases in Pd(II) reduction under acidic (pH 2.4) conditions was studied. While all three hydrogenases could contribute to Pd(II) reduction, the presence of either periplasmic hydrogenase (Hyd-1 or Hyd-2) was required to observe Pd(II) reduction rates comparable to the parent strain. An E. coli mutant strain genetically deprived of all hydrogenase activity showed negligible Pd(II) reduction. Electron microscopy suggested that the location of the resulting Pd(0) deposits was as expected from the subcellular localization of the particular hydrogenase involved in the reduction process. Membrane separation experiments established that Pd(II) reductase activity is membrane-bound and that hydrogenases are required to initiate Pd(II) reduction. The catalytic activity of the resulting Pd(0) nanoparticles in the reduction of Cr(VI) to Cr(III) varied according to the E. coli mutant strain used for the initial bioreduction of Pd(II). Optimum Cr(VI) reduction, comparable to that observed with a commercial Pd catalyst, was observed when the bio-Pd(0) catalytic particles were prepared from a strain containing an active Hyd-1. The results are discussed in the context of economic production of novel nanometallic catalysts.

The antimicrobial activity of nanoparticles: present situation and prospects for the future

“…Careful attention should thus be paid to the other physicochemical properties of NPs when exploring their antibacterial mechanisms. 150 …”

Biorefining of precious metals from wastes: an answer to manufacturing of cheap nanocatalysts for fuel cells and power generation via an integrated biorefinery?

“…In addition to D. desulfuricans and E. coli (Mikheenko et al 2008;Deplanche and Macaskie 2008;Deplanche et al 2010), other organisms with high hydrogenase activity, like Shewanella (De Windt et al, 2005) and Ralstonia (Ludwig et al 2009), can also reduce Pd(II) (Deplanche 2008). Cupriavidus (formerly Ralstonia) metallidurans can biomineralise gold by various mechanisms including its reduction to Au(0) (Reith et al 2009).…”

“…Catalytically active Pd(0) nanoparticles were manufactured by Desulfovibrio desulfuricans and also by E. coli (Deplanche, 2008;Orozco et al 2010), prompting the possibility to utilise waste E. coli biomass from biohydrogen production as the precursor to a fuel cell catalyst (Orozco et al 2010). Metallic NP synthesis is achieved by using hydrogenases (Mikheenko et al 2008;Deplanche et al 2010), expressed maximally under fermentative conditions (H 2 synthetic direction), to split H 2 (catabolic direction) and reduce, as electron acceptors, Pd(II) and Pt (IV) ions to Pd(0) and Pt(0) NPs.…”

Biological Synthesis of Metallic Nanoparticles by Bacteria, Fungi and Plants

“…The first is bioreduction, in which metal ions are chemically reduced into more stable forms biologically. Many organisms have the ability to utilise dissimilatory metal reduction, in which the reduction of a metal ion is coupled with the oxidation of an enzyme [20]. This results in stable and inert metallic nanoparticles that can then be safely removed from a contaminated sample.…”