Reduction of palladium and production of nano-catalyst by Geobacter sulfurreducens

The present study is the first report on the ability of Geobacter sulfurreducens PCA to reduce Pd(II) and produce Pd(0) nano-catalyst, using acetate as electron donor at neutral pH (7.0?±?0.1) and 30 °C. The microbial production of Pd(0) nanoparticles (NPs) was greatly enhanced by the presence of the redox mediator, anthraquinone-2,6-disulfonate (AQDS) when compared with controls lacking AQDS and cell-free controls. A cell dry weight (CDW) concentration of 800 mg/L provided a larger surface area for Pd(0) NPs deposition than a CDW concentration of 400 mg/L. Sample analysis by transmission electron microscopy revealed the formation of extracellular Pd(0) NPs ranging from 5 to 15 nm and X-ray diffraction confirmed the Pd(0) nature of the nano-catalyst produced. The present findings open the possibility for a new alternative to synthesize Pd(0) nano-catalyst and the potential application for microbial metal recovery from metal-containing waste streams.     

Diffusion of anionic and neutral GFP derivatives through plasmodesmata in epidermal cells of Nicotiana benthamiana

Plasmodesmata (Pd) are trans-wall membrane channels that permit cell-to-cell transport of metabolites and other small molecules, proteins, RNAs, and signaling molecules. The transport of cytoplasmic soluble macromolecules is a function of the electrochemical gradient between adjacent cells, the number of Pd per interface between adjacent cells, Stokes radius (R(S)), area of the cytoplasmic annulus, and channel length. The size of the largest molecule that can pass through Pd defines the Pd size exclusion limit. However, since the shape and size of a molecule determines its capacity to diffuse through pores or tubes, R(S) is a better measure. Relatively small changes in R(S) can cause large differences in the mobility of molecular probes, particularly if the pore size is close to that of the probe. In addition, as the dimensions of a macromolecule approach that of the channel, membrane charge effects may become important. We employed quantitative tools and molecular modeling to measure the apparent coefficient of conductivity of Pd, C(Pd), for the non-targeted transport of macromolecules. This method allowed us to examine the influence of protein charge and R(S) on C(Pd) in Nicotiana benthamiana. The C(Pd) of modified green fluorescent proteins (GFPs) of different sizes but with the same charge as native GFP and of a more negatively charged derivative were determined. We found that the C(Pd) of cytoplasmic soluble GFP and cytoplasmic forms of modified GFP were the most strongly correlated with R(S) and that the apparent aberrant increase in C(Pd) of a negatively charged GFP derivative was, at least in part, the result of the charge effect on R(S).     

Formation of palladium(0) nanoparticles at microbial surfaces

The increasing demand and limited natural resources for industrially important platinum‐group metal (PGM) catalysts render the recovery from secondary sources such as industrial waste economically interesting. In the process of palladium (Pd) recovery, microorganisms have revealed a strong potential. Hitherto, bacteria with the property of dissimilatory metal reduction have been in focus, although the biochemical reactions linking enzymatic Pd(II) reduction and Pd(0) deposition have not yet been identified. In this study we investigated Pd(II) reduction with formate as the electron donor in the presence of Gram‐negative bacteria with no documented capacity for reducing metals for energy production: Cupriavidus necator, Pseudomonas putida, and Paracoccus denitrificans. Only large and close‐packed Pd(0) aggregates were formed in cell‐free buffer solutions. Pd(II) reduction in the presence of bacteria resulted in smaller, well‐suspended Pd(0) particles that were associated with the cells (called “bioPd(0)” in the following). Nanosize Pd(0) particles (3–30 nm) were only observed in the presence of bacteria, and particles in this size range were located in the periplasmic space. Pd(0) nanoparticles were still deposited on autoclaved cells of C. necator that had no hydrogenase activity, suggesting a hydrogenase‐independent formation mechanism. The catalytic properties of Pd(0) and bioPd(0) were determined by the amount of hydrogen released in a reaction with hypophosphite. Generally, bioPd(0) demonstrated a lower level of activity than the Pd(0) control, possibly due to the inaccessibility of the Pd(0) fraction embedded in the cell envelope. Our results demonstrate the suitability of bacterial cells for the recovery of Pd(0), and formation and immobilization of Pd(0) nanoparticles inside the cell envelope. However, procedures to make periplasmic Pd(0) catalytically accessible need to be developed for future nanobiotechnological applications. Biotechnol. Bioeng. 2010;107: 206–215. © 2010 Wiley Periodicals, Inc.     

Palladium recovery by immobilized cells of Desulfovibrio desulfuricans using hydrogen as the electron donor in a novel electrobioreactor

Desulfovibrio desulfuricans reduces Pd(II) to Pd(0) at the expense of H₂. Mass transfer limits the rate under hydrogen in a static solution, while a bubble reactor was inefficient due to loss of H₂. A novel approach to the transfer of H₂ to the biomass utilized a biofilm on the surface of a Pd-Ag membrane that traps and transports atomic hydrogen (H), formed at the back-side electrochemically, for delivery to the immobilized biofilm to form a biocatalytic surface for reduction of Pd(II) and deposition of Pd(0). Separation of the primary electrolysis chamber from the biocatalytic chamber permits the use of different solutions and pH in each, and use of a low voltage for H₂ generation. Pd(0) recovery was efficient and fed by H₂ on demand to give a clean, economic system with no generation of secondary wastes. The system was tested against a precious metal processing waste where the continuous removal of Pd, Pt and Rh was up to 88%, 99% and 75%, respectively, at a flow residence time of 10–20 min at an input pH of 2.5 and a total metals concentration of approx. 5 mM. Biorecovered Pd(0) was a better chemical catalyst than its chemical counterpart in a test reaction which liberated H₂ from hypophosphite.     

From bio-mineralisation to fuel cells: biomanufacture of Pt and Pd nanocrystals for fuel cell electrode catalyst

Biosynthesis of nano-scale platinum and palladium was achieved via enzymatically-mediated deposition of metal ions from solution. The bio-accumulated Pt(0) and Pd(0) crystals were dried, applied onto carbon paper and tested as anodes in a polymer electrolyte membrane (PEM) fuel cell for power production. Up to 100% and 81% of the maximum power generation was achieved by the bio-Pt and bio-Pd catalysts, respectively, compared to commercial fuel cell grade Pt catalyst. Hence, biomineralisation could pave the way for economical production of fuel cell catalysts since previous studies have shown that precious metals can be biorecovered from wastes into catalytically active bionanomaterials.     

Tyrosine phosphorylation of PNS myelin P(0) occurs in the cytoplasmic domain and is maximal during early development

P(0), the major protein of PNS myelin, is considered to play a critical role in the compaction and stabilization of myelin lamellae. The protein undergoes extensive posttranslational modifications, including phosphorylation at multiple serine moieties in the cytoplasmic region. Recently, we demonstrated that P(0) is phosphorylated on one or more tyrosine residues in rat nerve homogenates after incubation. In this study, we show that P(0) phosphorylated on tyrosine is also present in the intact animal. The proportion of P(0) molecules phosphorylated on tyrosine is highest during the first postnatal week, a period that coincides with the most rapid period of myelin deposition in the PNS. A peptide that constitutes the cytoplasmic domain was isolated from purified P(0) and shown by immunochemical and chemical means to be phosphorylated on the tyrosine corresponding to Y(191) in the intact protein. No evidence was obtained supporting the possibility that P(0) is phosphorylated on other tyrosine residues. The sequence of amino acids surrounding Y(191) resemble known substrate phosphorylation sites for some nonreceptor cytoplasmic tyrosine kinases, as well as tyrosine-based recognition signals associated with clathrin vesicle-mediated cndocytosis.     

Palladium bionanoparticles production from acidic Pd(II) solutions and spent catalyst leachate using acidophilic Fe(III)-reducing bacteria

The acidophilic, Fe(III)-reducing heterotrophic bacteria Acidocella aromatica PFBC^T and Acidiphilium cryptum SJH were utilized to produce palladium (Pd) bionanoparticles via a simple 1-step microbiological reaction. Monosaccharide (or intracellular NADH)-dependent reactions lead to visualization of intra/extra-cellular enzymatic Pd(0) nucleation. Formic acid-dependent reactions proceeded via the first slow Pd(0) nucleation phase and the following autocatalytic Pd(II) reduction phase regardless of the presence or viability of the cells. However, use of active cells (with full enzymatic and membrane protein activities) at low formic acid concentration (5 mM) was critical to allow sufficient time for Pd(II) biosorption and the following enzymatic Pd(0) nucleation, which consequently enabled production of fine, dense and well-dispersed Pd(0) bionanoparticles. Differences of the resultant Pd(0) nanoparticles in size, density and localization between the two bacteria under each condition tested suggested different activity and location of enzymes and membrane “Pd(II) trafficking” proteins responsible for Pd(0) nucleation. Despite the inhibitory effect of leaching lixiviant and dissolved metal ions, Pd(0) bionanoparticles were effectively formed by active Ac. aromatica cells from both acidic synthetic Pd(II) solutions and from the actual spent catalyst leachates at equivalent 18–19 nm median size with comparable catalytic activity.

     

Reduction of Cr(VI) by "palladized" biomass of Desulfovibrio desulfuricans ATCC 29577

A novel catalytic activity of palladium [Pd(0)]-coated cells of Desulfovibrio desulfuricans ATCC 29577 ["bio-Pd(0)"] is demonstrated. Reduction of 700 microM Cr(VI) occurred within 24 h using formate (25 mM) or hydrogen (1 atm) as the electron donor, under conditions whereby cells lacking bound Pd(0), or palladium metal manufactured via chemical reduction of soluble Pd(II), did not reduce Cr(VI). The biomass-bound Pd(0) also functioned in the continuous removal of 400 microM Cr(VI) from a 1 mM solution under H(2) (flow residence time approximately 5 h), where chemically prepared Pd(0) was ineffective. This demonstrates a new type of active bioinorganic catalysis, whereby the presence of biomass bound to Pd(0) confers a novel catalytic capability not seen with Pd base metal or biomass alone.     

Bioreduction and biocrystallization of palladium by Desulfovibrio desulfuricans NCIMB 8307

The reduction of Pd(II) to Pd(0) was accelerated by using the sulfate-reducing bacterium Desulfovibrio desulfuricans NCIMB 8307 at the expense of formate or H(2) as electron donors at pH 2-7. With formate no reduction occurred at pH 2, but with H(2) 50% of the activity was retained at pH 2, with the maximum rate (1.3-1.4 micromol min(-1) mg dry cells(-1)) seen at pH 3-7, which was similar to the rate with formate at neutral pH. Excess nitrate was inhibitory to Pd(II) reduction using formate, but not H(2). Chloride ion was inhibitory as low as 100 mM using formate but with H(2) only ca. 25% inhibition was observed at 500 mM Cl(-) and H(2) was concluded to be the electron donor of choice for the potential remediation of industrial wastes. Deposited Pd was visible on the cells using transmission and scanning electron microscopy and analysis by energy dispersive X-ray microanalysis (EDAX) identified the deposit as Pd, confirmed as Pd(0) by X-ray powder diffraction analysis (XRD). The crystal size of the biodeposited Pd(0) was determined to be only 50% of the size of Pd(0) crystals manufactured chemically from Pd(II) at the expense of H(2) and, unlike the chemically manufactured material, the biocrystal size was independent of the pH. The "biological" Pd(0) functioned as a superior chemical catalyst in a test reaction which liberated hydrogen from hypophosphite. Pd, and also Pt and Rh, could be recovered by resting cell suspensions under H(2) from an industrial processing wastewater, suggesting a possible future application of bioprocessing technology for precious metals.     

Biological control of the size and reactivity of catalytic Pd(0) produced by Shewanella oneidensis

The interaction between Shewanella oneidensis MR-1 and the soluble metal Pd(II) during the reductive precipitation of Pd(0) determined the size and properties of the precipitated Pd(0) nanoparticles. Assessment of cell viability indicated that the bioreduction of Pd(II) was a detoxification mechanism depending on the Pd(II) concentration and on the presence and properties of the electron donor. The addition of H₂ in the headspace allowed S. oneidensis to resist the toxic effects of Pd(II). Interestingly, 25 mM formate was a less effective electron donor for bioreductive detoxification of Pd(II), since there was a 2 log reduction of culturable cells and a 20% decrease of viable cells within 60 min, followed by a slow recovery. When the ratio of Pd:cell dry weight (CDW) was below 5:2 at a concentration of 50 mg l⁻¹ Pd(II), most of the cells remained viable. These viable cells precipitated Pd(0) crystals over a relatively larger bacterial surface area and had a particle area that was up to 100 times smaller when compared to Pd(0) crystals formed on non-viable biomass (Pd:CDW ratio of 5:2). The relatively large and densely covering Pd(0) crystals on non-viable biomass exhibited high catalytic reactivity towards hydrophobic molecules such as polychlorinated biphenyls, while the smaller and more dispersed nanocrystals on a viable bacterial carrier exhibited high catalytic reactivity towards the reductive degradation of the anionic pollutant perchlorate.     

Manufacturing and characterization of Pd nanoparticles formed on immobilized bacterial cells

AIMS: To fabricate and analyse Pd nanoparticles on immobilized bacterial cells. METHODS AND RESULTS: Biological ceramic composites (biocers) were used as a template to produce Pd(0) nanoparticles. The metal-binding cells of the uranium mining waste pile isolate, Bacillus sphaericus JG-A12 were used as a biological component of the biocers and immobilized by using sol-gel technology. Vegetative cells and surface-layer proteins of this strain are known to bind high amounts of Pd(II) that can be reduced to Pd(0) particles by the addition of a reducing agent. Sorption of Pd(II) by the biocers from a metal complex solution was studied by inductively coupled plasma mass spectroscopy analyses. After embedding into sol-gel ceramics, the cells retained their Pd(II)-binding capability. Pd(0) nanoclusters were produced by the addition of hydrogen as reducing agent after the sorption of Pd(II). The interactions of Pd(0) with the biocers and the formed Pd(0) nanoparticles were investigated by extended X-ray absorption fine structure spectroscopy. The particles had a size of 0.6-0.8 nm. CONCLUSIONS: Bacterial cells that were immobilized by embedding into sol-gel ceramics were used as a template to produce Pd nanoclusters of a size smaller than 1 nm. These particles possess interesting physical and chemical properties. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of embedded bacterial cells as template enabled the fabrication of immobilized Pd(0) nanoparticles. These particles are highly interesting for technical applications, such as the development of novel catalysts.     

Comparison of amperometric biosensors fabricated by palladium sputtering, palladium electrodeposition and Nafion/carbon nanotube casting on screen-printed carbon electrodes

Different strategies, including palladium electrodeposition (Pd(CV)), Pd sputtering (Pd(S)) and Nafion-solubilized carbon nanotube casting (Nafion/CNT), were used to modify screen-printed carbon electrodes (SPCEs) for the fabrication of amperometric enzyme biosensors. The electrochemical properties of the bare and modified SPCEs and the optimal conditions for surface modification were determined. The electrochemical response of the bare SPCE to H(2)O(2) under the potential of 0.3 V could be improved about 100-fold by Pd modification by electrodeposition or sputtering. By contrast, the electrochemical response of the bare SPCE was enhanced by only about 11-fold by Nafion/CNT casting. Moreover, the Pd(CV)-SPCEs exhibited better reproducibility of electrochemical response (a relative standard deviation (R.S.D.)<6.0%) than freshly prepared Pd(S)-SPCEs (R.S.D.>10%). The glucose biosensor fabricated from Pd-modified electrodes could be stored for up to 108 days without loosing significant activity. The Pd(CV)-SPCE also showed very reliable signal characteristics upon 50 consecutively repeated measurements of ascorbic acid. The electrocatalytic detection of the Pd-SPCE was combined with additional advantages of resistance to surface fouling and hence good stability. In conclusion, this study demonstrated that deposition of Pd thin film on SPCEs by electrodeposition or sputtering provided superior enhancement of electrochemical properties compared to Nafion/CNT-SPCEs. Despite their high electrochemical response, Pd(S)-SPCEs required an activation process to improve stability and Pd(CV)-SPCEs suffered from poor between electrode reproducibility.     

Palladium and gold removal and recovery from precious metal solutions and electronic scrap leachates by Desulfovibrio desulfuricans

Biomass of Desulfovibrio desulfuricans was used to recover Au(III) as Au(0) from test solutions and from waste electronic scrap leachate. Au(0) was precipitated extracellularly by a different mechanism from the biodeposition of Pd(0). The presence of Cu²⁺ (∼2000 mg/l) in the leachate inhibited the hydrogenase-mediated removal of Pd(II) but pre-palladisation of the cells in the absence of added Cu²⁺ facilitated removal of Pd(II) from the leachate and more than 95% of the Pd(II) was removed autocatalytically from a test solution supplemented with Cu(II) and Pd(II). Metal recovery was demonstrated in a gas-lift electrobioreactor with electrochemically generated hydrogen, followed by precipitation of recovered metal under gravity. A 3-stage bioseparation process for the recovery of Au(III), Pd(II) and Cu(II) is proposed.Victoria S. Baxter-Plant – Deceased     

Continuous removal of Cr(VI) from aqueous solution catalysed by palladised biomass of Desulfovibrio vulgaris

Growth-decoupled cells of Desulfovibrio vulgaris NCIMB 8303 can be used to reduce Pd(II) to cell-bound Pd(0) (Bio-Pd(0)), a bioinorganic catalyst capable of reducing hexavalent chromium to less toxic Cr(III), using formate as the electron donor. Magnetic resonance imaging showed that Bio-Pd(0), immobilized in chitosan and agar beads, is distinguishable from the surrounding gel and is evenly dispersed within the immobilization matrix. Agar-immobilized Bio-Pd(0) and 'chemical Pd(0)' were packed into continuous-flow reactors, and challenged with a solution containing 100 microM Cr(VI) (pH 7) at a flow rate of 2.4 ml h(-1). Agar-immobilized chemical Pd(0) columns lost Cr(VI) reducing ability by 160 h, whereas columns containing immobilized Bio-Pd(0) maintained 90% reduction until 680 h, after which reduction efficiency was gradually lost.     

Non-enzymatic palladium recovery on microbial and synthetic surfaces

The use of microorganisms as support for reduction of dissolved Pd(II) to immobilized Pd(0) nanoparticles is an environmentally friendly approach for Pd recovery from waste. To better understand and engineer Pd(0) nanoparticle synthesis, one has to consider the mechanisms by which Pd(II) is reduced on microbial surfaces. Escherichia coli, Shewanella oneidensis, and Pseudomonas putida were used as model organisms in order to elucidate the role of microbial cells in Pd(II) reduction under acidic conditions. Pd(II) was reduced by formate under acidic conditions, and the process occurred substantially faster in the presence of cells as compared to cell-free controls. We found no difference between native (untreated) and autoclaved cells, and could demonstrate that even a non-enzymatic protein (bovine serum albumin) stimulated Pd(II) reduction as efficiently as bacterial cells. Amine groups readily interact with Pd(II), and to specifically test their role in surface-assisted Pd(II) reduction by formate, we replaced bacterial cells with polystyrene microparticles functionalized with amine or carboxyl groups. Amine-functionalized microparticles had the same effect on Pd(II) reduction as bacterial cells, and the effect could be hampered if the amine groups were blocked by acetylation. The interaction with amine groups was confirmed by infrared spectroscopy on whole cells and amine-functionalized microparticles. In conclusion, bio-supported Pd(II) reduction on microbial surfaces is possibly mediated by a non-enzymatic mechanism. We therefore suggest the use of amine-rich biomaterials rather than intact cells for Pd bio-recovery from waste.     

Tobacco mosaic virus (TMV) replicase and movement protein function synergistically in facilitating TMV spread by lateral diffusion in the plasmodesmal desmotubule of Nicotiana benthamiana

Virus spread through plasmodesmata (Pd) is mediated by virus-encoded movement proteins (MPs) that modify Pd structure and function. The MP of Tobacco mosaic virus ((TMV)MP) is an endoplasmic reticulum (ER) integral membrane protein that binds viral RNA (vRNA), forming a vRNA:MP:ER complex. It has been hypothesized that (TMV)MP causes Pd to dilate, thus potentiating a cytoskeletal mediated sliding of the vRNA:MP:ER complex through Pd; in the absence of MP, by contrast, the ER cannot move through Pd. An alternate model proposes that cell-to-cell spread takes place by diffusion of the MP:vRNA complex in the ER membranes which traverse Pd. To test these models, we measured the effect of (TMV)MP and replicase expression on cell-to-cell spread of several green fluorescent protein-fused probes: a soluble cytoplasmic protein, two ER lumen proteins, and two ER membrane-bound proteins. Our data support the diffusion model in which a complex that includes ER-embedded MP, vRNA, and other components diffuses in the ER membrane within the Pd driven by the concentration gradient between an infected cell and adjacent noninfected cells. The data also suggest that the virus replicase and MP function together in altering Pd conductivity.     

Biorefining of platinum group metals from model waste solutions into catalytically active bimetallic nanoparticles

Bacteria can fabricate platinum group metal (PGM) catalysts cheaply, a key consideration of industrial processes and waste decontaminations. Biorecovery of PGMs from wastes is promising but PGM leachates made from metallic scraps are acidic. A two‐step biosynthesis ‘pre‐seeds’ metallic deposits onto bacterial cells benignly; chemical reduction of subsequent metal from acidic solution via the seeds makes bioscaffolded nanoparticles (NPs). Cells of Escherichia coli were seeded using Pd(II) or Pt(IV) and exposed to a mixed Pd(II)/Pt(IV) model solution under H₂ to make bimetallic catalyst. Its catalytic activity was assessed in the reduction of Cr(VI), with 2 wt% or 5 wt% preloading of Pd giving the best catalytic activity, while 1 wt% seeds gave a poorer catalyst. Use of Pt seeds gave less effective catalyst in the final bimetallic catalyst, attributed to fewer and larger initial seeds as shown by electron microscopy, which also showed a different pattern of Pd and Pt deposition. Bimetallic catalyst (using cells preloaded with 2 wt% Pd) was used in the hydrogenation of soybean oil which was enhanced by ~fourfold using the bimetallic catalyst made from a model waste solution as compared to 2 wt% Pd preloaded cells alone, with a similar selectivity to cis C18:1 product as found using a Pd‐Al₂O₃ commercial catalyst.     

Determination of formation constants for complexes of very high stability: log β4 for the [Pd(CN)4] ion

The formation constant, log β₄ = 62.3 for [Pd(CN)₄]²⁻ is reported at 25 °C in 0.1 M NaClO₄. This value of log β₄ was determined using a competition reaction, monitored using UV-Vis spectroscopy and ¹H NMR. The competition reaction used was with the tetraamine ligand 2,3,2-tet(1,4,8,11-tetraazaundecane), for which log K₁ = 47.8 at 25 °C in 0.1 M NaClO₄ was determined by competition with thiocyanate, as described by earlier workers (Q.Y. Yan, G. Anderegg, Inorg. Chim. Acta 105 (1985) 121.). Also reported is a value of log β₄ for the [Pd(SCN)₄]²⁻ ion of 27.2 in 0.1 M NaClO₄, determined by competition with 2,2,2-tet. Measurement of log K₁ for cyclam with Pd(II) was attempted using a competition reaction with cyanide, combined with the very high value of log β₄ for [Pd(CN)₄]²⁻ measured here. It appeared that the equilibrium being followed was actually [Pd(cyclam)]²⁺ + 2CN⁻ ? [Pd(cyclam)(CN)₂], for which a constant of log K = 5.2 was obtained. ¹H NMR and IR studies suggested that the complex [Pd(cyclam)(CN)₂] was prone to oxidation to Pd(IV), followed by disproportionation to [Pd(cyclam)]²⁺ and, presumably, (CN)₂. The very high value of log β₄ for [Pd(CN)₄]²⁻ found here appears to be the highest formation constant known for any metal ion.     

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

Bio-manufacturing of nano-scale palladium was achieved via enzymatically-mediated deposition of Pd from solution using Desulfovibrio desulfuricans, Escherichia coli and Cupriavidus metallidurans. Dried ‘Bio-Pd’ materials were sintered, applied onto carbon papers and tested as anodes in a proton exchange membrane (PEM) fuel cell for power production. At a Pd(0) loading of 25% by mass the fuel cell power using Bio-Pd _{D. desulfuricans} (positive control) and Bio-Pd _{E. coli} (negative control) was ~140 and ~30 mW respectively. Bio-Pd _{C. metallidurans} was intermediate between these with a power output of ~60 mW. An engineered strain of E. coli (IC007) was previously reported to give a Bio-Pd that was >3-fold more active than Bio-Pd of the parent E. coli MC4100 (i.e. a power output of >110 mW). Using this strain, a mixed metallic catalyst was manufactured from an industrial processing waste. This ‘Bio-precious metal’ (‘Bio-PM’) gave ~68% of the power output as commercial Pd(0) and ~50% of that of Bio-Pd _{D. desulfuricans} when used as fuel cell anodic material. The results are discussed in relation to integrated bioprocessing for clean energy.