A Novel Aerobic Mechanism for Reductive Palladium Biomineralization and Recovery by Escherichia coli

Joanne M Foulkes,Kevin Deplanche,Frank Sargent,Lynne E Macaskie,Jonathan R Lloyd

doi:10.1080/01490451.2015.1069911

Joanne M Foulkes, Kevin Deplanche + Show 3 more

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https://doi.org/10.1080/01490451.2015.1069911

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Abstract

ABSTRACTAerobically grown E. coli cells reduced Pd(II) via a novel mechanism using formate as the electron donor. This reduction was monitored in real-time using extended X-ray absorption fine structure. Transmission electron microscopy analysis showed that Pd(0) nanoparticles, confirmed by X-ray diffraction, were precipitated outside the cells. The rate of Pd(II) reduction by E. coli mutants deficient in a range of oxidoreductases was measured, suggesting a molybdoprotein-mediated mechanism, distinct from the hydrogenase-mediated Pd(II) reduction previously described for anaerobically grown E. coli cultures. The potential implications for Pd(II) recovery and bioPd catalyst fabrication are discussed.

Highlights

The microbial reduction of metals and radionuclides has attracted much interest, as it can be potentially harnessed for bioremediation, metal recovery, the fabrication of novel nanobiominerals and even energy generation in biobatteries (Lloyd 2003; Lloyd et al 2008; Lovley 2006;)
Strain MC4100 ∆moaA, lacking all molybdoenzymes, reduced the palladium within 7 h. These results indicate the likely involvement of the formate dehydrogenase (FDH-O) enzyme in the reduction of Pd(II) by aerobically-grown E. coli using formate, other Mocontaining enzymes must be involved given the impaired metal reduction noted w ie ly
The results from this study demonstrate that it is possible for aerobically-grown cultures of E. coli to reduce Pd(II) enzymatically, with no need to remove oxygen from the experimental system during the bioreduction step

Summary

Introduction

The microbial reduction of metals and radionuclides has attracted much interest, as it can be potentially harnessed for bioremediation, metal recovery, the fabrication of novel nanobiominerals and even energy generation in biobatteries (Lloyd 2003; Lloyd et al 2008; Lovley 2006;). Shewanella oneidensis (De Windt et al 2005), Escherichia coli (Deplanche et al.2010, 2014; Mabbett et al 2006), Pseudomonas putida, Cupriavidus necator (Søbjerg et al 2009), Cupriavidus metallidurans (Gauthier et al 2010), Paracoccus denitrificans (Bunge et al 2010), Rhodobacter sphaeroides (Redwood et al 2008), Rhodobacter capsulatus (Wood et al 2010), and the Gram-positive bacteria Bacillus sphaericus (Creamer et al 2007), Arthrobacter oxyidans (Deplanche et al 2014; Wood et al 2010), Micrococcus luteus (Deplanche et al 2014), Staphylococcus sciuri (Søbjerg et al 2009) and Clostridium pasteurianum (Chidambaram et al 2010) This property has allowed the use of ‘palladised’ whole cells or processed biomineral directly in industrially important reactions, often showing superior activity compared w. A number of studies have investigated the catalytic activity of bioPd, demonstrating its use in remediative reactions such as the reduction of Cr(VI) to Cr(III) (Beauregard et al.2010; Mabbett et al 2006), the dehalogenation of chlorophenol, polychlorinated biphenyls, polybrominated diphenyl ethers (Baxter-Plant et al 2003; De Windt et al.2005; Harrad et al 2007), trichloroethylene (Hennebel et al 2009a, 2009b), and the pesticide γ- hexachlorocyclohexane (Mertens et al 2007), in ‘greener’ chemical synthesis such as the hydrogenation of itaconic acid (Creamer et al 2007) and 2-

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