Direct solid state NMR observation of the 105Pd nucleus in inorganic compounds and palladium metal systems.

The ability to clearly relate local structure to function is desirable for many catalytically relevant Pd-containing systems. This report represents the first direct 105Pd solid state NMR measurements of diamagnetic inorganic (K2Pd(iv)Cl6, (NH4)2Pd(iv)Cl6 and K2Pd(iv)Br6) complexes, and micron- and nano-sized Pd metal particles at room temperature, thereby introducing effective 105Pd chemical shift and Knight shift ranges in the solid state. The very large 105Pd quadrupole moment (Q) makes the quadrupole parameters (CQ, ηQ) extremely sensitive to small structural distortions. Despite the well-defined high symmetry octahedral positions describing the immediate Pd coordination environment, 105Pd NMR measurements can detect longer range disorder and anisotropic motion in the interstitial positions. The approach adopted here combines high resolution X-ray pair distribution function (PDF) analyses with 105Pd, 39K and 35Cl MAS NMR, and shows solid state NMR to be a very sensitive probe of short range structural perturbations. Solid state 105Pd NMR observations of ∼44-149 µm Pd sponge, ∼20-150 nm Pd black nanoparticles, highly monodisperse 16 ± 3 nm PVP-stabilised Pd nanoparticles, and highly polydisperse ∼2-1100 nm biomineralized Pd nanoparticles (bio-Pd) on pyrolysed amorphous carbon detect physical differences between these systems based on relative bulk:surface ratios and monodispersity/size homogeneity. This introduces the possibility of utilizing solid state NMR to help elucidate the structure-function properties of commercial Pd-based catalyst systems.

Harnessing water fleas for water reclamation: A nature-based tertiary wastewater treatment technology.

Urbanisation, population growth, and climate change have put unprecedented pressure on water resources, leading to a global water crisis and the need for water reuse. However, water reuse is unsafe unless persistent chemical pollutants are removed from reclaimed water. State-of-the-art technologies for the reduction of persistent chemical pollutants in wastewater typically impose high operational and energy costs and potentially generate toxic by-products (e.g., bromate from ozonation). Nature-base solutions are preferred to these technologies for their lower environmental impact. However, so far, bio-based tertiary wastewater treatments have been inefficient for industrial-scale applications. Moreover, they often demand significant financial investment and large infrastructure, undermining sustainability objectives. Here, we present a scalable, low-cost, low-carbon, and retrofittable nature-inspired solution to remove persistent chemical pollutants (pharmaceutical, pesticides and industrial chemicals). We showed Daphnia's removal efficiency of individual chemicals and chemicals from wastewater at laboratory scale ranging between 50 % for PFOS and 90 % for diclofenac. We validated the removal efficiency of diclofenac at prototype scale, showing sustained performance over four weeks in outdoor seminatural conditions. A techno-commercial analysis on the Daphnia-based technology suggested several technical, commercial and sustainability advantages over established and emerging treatments at comparable removal efficiency, benchmarked on available data on individual chemicals. Further testing of the technology is underway in open flow environments holding real wastewater. The technology has the potential to improve the quality of wastewater effluent, meeting requirements to produce water appropriate for reuse in irrigation, industrial application, and household use. By preventing persistent chemicals from entering waterways, this technology has the potential to maximise the shift to clean growth, enabling water reuse, reducing resource depletion and preventing environmental pollution.

Biosynthesis of platinum nanoparticles by Escherichia coli MC4100: can such nanoparticles exhibit intrinsic surface enantioselectivity?

The biomanufacture of two types of platinum bionanoparticle (bioNP) using Escherichia coli MC4100(1% and 20% by mass metal loading) together with a method for both liberating the nanoparticles (NPs) from the bacterial layer and their subsequent critical cleaning is reported. The possibility of an enantiomeric excess of chiral kink sites forming on the surface of the Pt nanoparticles produced by the bacteria was investigated using the electrooxidation of D- and L-glucose as the chiral probe. Transmission electron microscopy revealed that the Pt bioNPs (after recovery and cleaning) were typically 2.3 ± 0.7 nm (1% loading) and 4.5 ± 0.7 nm (20% loading) in diameter. The D- and L-glucose electrooxidation measurements did not give rise to any chiral response using either of the Pt bioNPs types but did display differing CV profiles. This suggested that the overall surface morphology of each bioNP could be controlled by the degree of metal loading but that no enantiomeric excess of intrinsically chiral surface kink sites was present.

Enhanced photosynthetic output via dichroic beam-sharing.

Microbial solar biofuels offer great promise for future sustainable food, fuels and chemicals but are limited by low productivities and a requirement for large land areas to harvest sunlight. A 71 % increase in combined photosynthetic activity was achieved by illuminating both Rhodobacter sphaeroides and Arthrospira (Spirulina) platensis from a single beam of simulated sunlight, divided using a dichroic mirror. Therefore, this technique is termed 'dichroic beam-sharing', in which the complementary action spectra of two different useful micro-organisms, belonging to green and purple groups, is exploited and allows a single beam of sunlight to be shared efficiently between separate photobioreactors. Because the action spectra of these two organisms are typical of large groups, this novel method could increase the productivity of photosynthetic micro-organisms in the production of diverse commodities.

Nano-crystalline hydroxyapatite bio-mineral for the treatment of strontium from aqueous solutions.

Hydroxyapatites were analysed using electron microscopy, X-ray diffraction (XRD) and X-ray fluorescence (XRF) analysis. Examination of a bacterially produced hydroxyapatite (Bio-HA) by scanning electron microscopy showed agglomerated nano-sized particles; XRD analysis confirmed that the Bio-HA was hydroxyapatite, with an organic matter content of 7.6%; XRF analysis gave a Ca/P ratio of 1.55, also indicative of HA. The size of the Bio-HA crystals was calculated as ~25 nm from XRD data using the Scherrer equation, whereas Comm-HA powder size was measured as ≤ 50 µm. The nano-crystalline Bio-HA was ~7 times more efficient in removing Sr(2+) from synthetic groundwater than Comm-HA. Dissolution of HA as indicated by the release of phosphate into the solution phase was higher in the Comm-HA than the Bio-HA, indicating a more stable biomaterial which has a potential for the remediation of contaminated sites.

Local magnetism in palladium bionanomaterials probed by muon spectroscopy.

Palladium bionanomaterial was manufactured using the sulfate-reducing bacterium, Desulfovibrio desulfuricansm, to reduce soluble Pd(II) ions to cell-bound Pd(0) in the presence of hydrogen. The biomaterial was examined using a Superconducting Quantum Interference Device (SQUID) to measure bulk magnetisation and by Muon Spin Rotation Spectroscopy (µSR) which is uniquely able to probe the local magnetic environment inside the sample. Results showed behaviour attributable to interaction of muons both with palladium electrons and the nuclei of hydrogen trapped in the particles during manufacture. Electronic magnetism, also suggested by SQUID, is not characteristic of bulk palladium and is consistent with the presence of nanoparticles previously seen in electron micrographs. We show the first use of µSR as a tool to probe the internal magnetic environment of a biologically-derived nanocatalyst material.

Enhanced hydrogenation catalyst synthesized by Desulfovibrio desulfuricans exposed to a radio frequency magnetic field.

Desulfovibrio desulfuricans reduces Pd(II) to Pd(0)-nanoparticles (Pd-NPs) which are catalytically active in 2-pentyne hydrogenation. To make Pd-NPs, resting cells are challenged with Pd(II) ions (uptake), followed by addition of electron donor to promote bioreduction of cell-bound Pd(II) to Pd(0) (bio-Pd). Application of radiofrequency (RF) radiation to prepared 5 wt% bio-Pd catalyst (60 W power, 60 min) increased the hydrogenation rate by 70% with no adverse impact on selectivity to cis-2-pentene. Such treatment of a 5 wt% Pd/carbon commercial catalyst did not affect the conversion rate but reduced the selectivity. Lower-dose RF radiation (2-8 W power, 20 min) was applied to the bacteria at various stages before and during synthesis of the bio-scaffolded Pd-NPs. The reaction rate (µ mol 2-pentyne converted s-1 ) was increased by ~threefold by treatment during bacterial catalyst synthesis. Application of RF radiation (2 or 4 W power) to resting cells prior to Pd(II) exposure affected the catalyst made subsequently, increasing the reaction rate by 50% as compared to untreated cells, while nearly doubling selectivity for cis 2-pentene. The results are discussed with respect to published and related work which shows altered dispersion of the Pd-NPs made following or during RF exposure.

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

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.

Accumulation of zirconium phosphate by a Serratia sp.: a benign system for the removal of radionuclides from aqueous flows.

Metal phosphate deposited enzymatically on Serratia sp. has been used successfully for the removal of radionuclides from aqueous flows. Previous studies using biogenic hydrogen uranyl phosphate (HUP) on Serratia sp. biofilm showed removal of 100% of (90)Sr, (137)Cs, and (60)Co via their intercalation into biogenic HUP crystals. Zirconium phosphates (ZrP) offer a potential non-toxic and non-radioactive alternative to HUP for water decontamination. A method was developed for biomanufacturing ZrP. Biogenic ZrP removed ca. 100% of Sr(2+) and Co(2+) (0.5 mM) from solutions to a molar ratio at saturation of ca. 1:0.6 for both Zr:Sr and Zr:Co. The potential for drinking water decontamination via bio-ZrP is discussed with respect to bio-HUP and also other commercially available materials.

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.

Characterization of Palladium Nanoparticles Produced by Healthy and Microwave-Injured Cells of Desulfovibrio desulfuricans and Escherichia coli.

Numerous studies have focused on the bacterial synthesis of palladium nanoparticles (bio-Pd NPs), via uptake of Pd (II) ions and their enzymatically-mediated reduction to Pd (0). Cells of Desulfovibrio desulfuricans (obligate anaerobe) and Escherichia coli (facultative anaerobe, grown anaerobically) were exposed to low-dose radiofrequency (RF) radiation(microwave (MW) energy) and the biosynthesized Pd NPs were compared. Resting cells were exposed to microwave energy before Pd (II)-challenge. MW-injured Pd (II)-treated cells (and non MW-treated controls) were contacted with H2 to promote Pd(II) reduction. By using scanning transmission electron microscopy (STEM) associated with a high-angle annular dark field (HAADF) detector and energy dispersive X-ray (EDX) spectrometry, the respective Pd NPs were compared with respect to their mean sizes, size distribution, location, composition, and structure. Differences were observed following MWinjury prior to Pd(II) exposure versus uninjured controls. With D. desulfuricans the bio-Pd NPs formed post-injury showed two NP populations with different sizes and morphologies. The first, mainly periplasmically-located, showed polycrystalline Pd nano-branches with different crystal orientations and sizes ranging between 20 and 30 nm. The second NPpopulation, mainly located intracellularly, comprised single crystals with sizes between 1 and 5 nm. Bio-Pd NPs were produced mainly intracellularly by injured cells of E. coli and comprised single crystals with a size distribution between 1 and 3 nm. The polydispersity index was reduced in the bio-Pd made by injured cells of E. coli and D. desulfuricans to 32% and 39%, respectively, of the values of uninjured controls, indicating an increase in NP homogeneity of 30-40% as a result of the prior MWinjury. The observations are discussed with respect to the different locations of Pd(II)-reducing hydrogenases in the two organisms and with respect to potential implications for the catalytic activity of the produced NPs following injury-associated altered NP patterning.

Novel catalytically active Pd/Ru bimetallic nanoparticles synthesized by Bacillus benzeovorans.

Bacillus benzeovorans assisted and supported growth of ruthenium (bio-Ru) and palladium/ruthenium (bio-Pd@Ru) core@shell nanoparticles (NPs) as bio-derived catalysts. Characterization of the bio-NPs using various electron microscopy techniques and high-angle annular dark field (HAADF) analysis confirmed two NP populations (1-2 nm and 5-8 nm), with core@shells in the latter. The Pd/Ru NP lattice fringes, 0.231 nm, corresponded to the (110) plane of RuO2. While surface characterization using X-ray photoelectron spectroscopy (XPS) showed the presence of Pd(0), Pd(II), Ru(III) and Ru(VI), X-ray absorption (XAS) studies of the bulk material confirmed the Pd speciation (Pd(0) and Pd(II)- corresponding to PdO), and identified Ru as Ru(III) and Ru(IV). The absence of Ru-Ru or Ru-Pd peaks indicated Ru only exists in oxide forms (RuO2 and RuOH), which are surface-localized. X ray diffraction (XRD) patterns did not identify Pd-Ru alloying. Preliminary catalytic studies explored the conversion of 5-hydroxymethyl furfural (5-HMF) to the fuel precursor 2,5-dimethyl furan (2,5-DMF). Both high-loading (9.7 wt.% Pd, 6 wt.% Ru) and low-loading (2.4 wt.% Pd, 2 wt.% Ru) bio-derived catalysts demonstrated high conversion efficiencies (~95%) and selectivity of ~63% (~20% better than bio-Ru NPs) and 58%, respectively. These materials show promising future scope as efficient low-cost biofuel catalysts.

Synthesis of Pd/Ru Bimetallic Nanoparticles by Escherichia coli and Potential as a Catalyst for Upgrading 5-Hydroxymethyl Furfural Into Liquid Fuel Precursors.

Escherichia coli cells support the nucleation and growth of ruthenium and ruthenium-palladium nanoparticles (Bio-Ru and Bio-Pd/Ru NPs). We report a method for the synthesis of these monometallic and bimetallic NPs and their application in the catalytic upgrading of 5-hydroxymethyl furfural (5-HMF) to 2,5 dimethylfuran (DMF). Examination using high resolution transmission electron microscopy with energy dispersive X-ray microanalysis (EDX) and high angle annular dark field (HAADF) showed Ru NPs located mainly at the cell surface using Ru(III) alone but small intracellular Ru-NPs (size ∼1-2 nm) were visible only in cells that had been pre-"seeded" with Pd(0) (5 wt%) and loaded with equimolar Ru. Pd(0) NPs were distributed between the cytoplasm and cell surface. Cells bearing 5% Pd/5% Ru showed some co-localization of Pd and Ru but chance associations were not ruled out. Cells loaded to 5 wt% Pd/20 wt% Ru showed evidence of core-shell structures (Ru core, Pd shell). Examination of this cell surface material using X-ray photoelectron spectroscopy (XPS) showed Pd(0) and Pd(II) and Ru(IV) and Ru(III), with confirmation by analysis of bulk material using X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses. Both Bio-Ru NPs and Bio-Pd/Ru NPs were active in the conversion of 5-HMF into 2,5-DMF but commercial Ru on carbon catalyst outperformed 5 wt% bio-Ru by fourfold. While 5 wt% Pd/20 wt% Ru achieved 20% yield of DMF the performance of the 5 wt% Pd/5 wt% Ru bio-catalyst was higher and comparable to the commercial 5 wt% Ru/C catalyst in a test reaction using commercial 5-HMF (>50% selectivity). 5-HMF was prepared by thermochemical hydrolysis of starch and cellulose with solvent extraction of 5-HMF into methyltetrahydrofuran (MTHF). Here, with MTHF as the reaction solvent the commercial Ru/C catalyst had little activity (100% conversion, negligible selectivity to DMF) whereas the 5 wt% Pd/5 wt% Ru bio-bimetallic gave 100% conversion and 14% selectivity to DMF from material extracted from hydrolyzates. The results indicate a potential green method for realizing increased energy potential from biomass wastes as well as showing a bio-based pathway to manufacturing a scarcely described bimetallic material.

Upconversion of Cellulosic Waste Into a Potential "Drop in Fuel" via Novel Catalyst Generated Using Desulfovibrio desulfuricans and a Consortium of Acidophilic Sulfidogens.

Biogas-energy is marginally profitable against the "parasitic" energy demands of processing biomass. Biogas involves microbial fermentation of feedstock hydrolyzate generated enzymatically or thermochemically. The latter also produces 5-hydroxymethyl furfural (5-HMF) which can be catalytically upgraded to 2, 5-dimethyl furan (DMF), a "drop in fuel." An integrated process is proposed with side-stream upgrading into DMF to mitigate the "parasitic" energy demand. 5-HMF was upgraded using bacterially-supported Pd/Ru catalysts. Purpose-growth of bacteria adds additional process costs; Pd/Ru catalysts biofabricated using the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans were compared to those generated from a waste consortium of acidophilic sulfidogens (CAS). Methyl tetrahydrofuran (MTHF) was used as the extraction-reaction solvent to compare the use of bio-metallic Pd/Ru catalysts to upgrade 5-HMF to DMF from starch and cellulose hydrolyzates. MTHF extracted up to 65% of the 5-HMF, delivering solutions, respectively, containing 8.8 and 2.2 g 5-HMF/L MTHF. Commercial 5% (wt/wt) Ru-carbon catalyst upgraded 5-HMF from pure solution but it was ineffective against the hydrolyzates. Both types of bacterial catalyst (5wt%Pd/3-5wt% Ru) achieved this, bio-Pd/Ru on the CAS delivering the highest conversion yields. The yield of 5-HMF from starch-cellulose thermal treatment to 2,5 DMF was 224 and 127 g DMF/kg extracted 5-HMF, respectively, for CAS and D. desulfuricans catalysts, which would provide additional energy of 2.1 and 1.2 kWh/kg extracted 5-HMF. The CAS comprised a mixed population with three patterns of metallic nanoparticle (NP) deposition. Types I and II showed cell surface-localization of the Pd/Ru while type III localized NPs throughout the cell surface and cytoplasm. No metallic patterning in the NPs was shown via elemental mapping using energy dispersive X-ray microanalysis but co-localization with sulfur was observed. Analysis of the cell surfaces of the bulk populations by X-ray photoelectron spectroscopy confirmed the higher S content of the CAS bacteria as compared to D. desulfuricans and also the presence of Pd-S as well as Ru-S compounds and hence a mixed deposit of PdS, Pd(0), and Ru in the form of various +3, +4, and +6 oxidation states. The results are discussed in the context of recently-reported controlled palladium sulfide ensembles for an improved hydrogenation catalyst.

Dissecting the roles of Escherichia coli hydrogenases in biohydrogen production.

Escherichia coli can perform at least two modes of anaerobic hydrogen metabolism and expresses at least two types of hydrogenase activity. Respiratory hydrogen oxidation is catalysed by two 'uptake' hydrogenase isoenzymes, hydrogenase -1 and -2 (Hyd-1 and -2), and fermentative hydrogen production is catalysed by Hyd-3. Harnessing and enhancing the metabolic capability of E. coli to perform anaerobic mixed-acid fermentation is therefore an attractive approach for bio-hydrogen production from sugars. In this work, the effects of genetic modification of the genes encoding the uptake hydrogenases, as well as the importance of preculture conditions, on hydrogen production and fermentation balance were examined. In suspensions of resting cells pregrown aerobically with formate, deletions in Hyd-3 abolished hydrogen production, whereas the deletion of both uptake hydrogenases improved hydrogen production by 37% over the parent strain. Under fermentative conditions, respiratory H2 uptake activity was absent in strains lacking Hyd-2. The effect of a deletion in hycA on H2 production was found to be dependent upon environmental conditions, but H2 uptake was not significantly affected by this mutation.

Biomass-supported palladium catalysts on Desulfovibrio desulfuricans and Rhodobacter sphaeroides.

A Rhodobacter sphaeroides-supported dried, ground palladium catalyst ("Rs-Pd(0)") was compared with a Desulfovibrio desulfuricans-supported catalyst ("Dd-Pd(0)") and with unsupported palladium metal particles made by reduction under H2 ("Chem-Pd(0)"). Cell surface-located clusters of Pd(0) nanoparticles were detected on both D. desulfuricans and R. sphaeroides but the size and location of deposits differed among comparably loaded preparations. These differences may underlie the observation of different activities of Dd-Pd(0) and Rs-Pd(0) when compared with respect to their ability to promote hydrogen release from hypophosphite and to catalyze chloride release from chlorinated aromatic compounds. Dd-Pd(0) was more effective in the reductive dehalogenation of polychlorinated biphenyls (PCBs), whereas Rs-Pd(0) was more effective in the initial dehalogenation of pentachlorophenol (PCP) although the rate of chloride release from PCP was comparable with both preparations after 2 h.

Manufacture of stable palladium and gold nanoparticles on native and genetically engineered flagella scaffolds.

The use of bacterial flagella as templates for the immobilization of Pd and Au nanoparticles is described. Complete coverage of D. desulfuricans flagellar filaments by Pd(0) nanoparticles was obtained via the H(2)-mediated reduction of Pd(NH3)4]Cl2 but similar results were not obtained using HAuCl4. The introduction of additional cysteine-derived thiol residues in the E. coli FliC protein increased Au(III) sorption and reduction onto the surface of the flagellar filament and resulted in the production of stabilized Au(0) nanoparticles of approximately 20-50 nm diameter. We demonstrate the application of molecular engineering techniques to manufacture biologically passivated Au(0) nanoparticles of a size suitable for catalytic applications.

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-Al2 O3 commercial catalyst.

Advances and bottlenecks in microbial hydrogen production.

Biological production of hydrogen is poised to become a significant player in the future energy mix. This review highlights recent advances and bottlenecks in various approaches to biohydrogen processes, often in concert with management of organic wastes or waste CO2 . Some key bottlenecks are highlighted in terms of the overall energy balance of the process and highlighting the need for economic and environmental life cycle analyses with regard also to socio-economic and geographical issues.

Metallic bionanocatalysts: potential applications as green catalysts and energy materials.

Microbially generated or supported nanocatalysts have potential applications in green chemistry and environmental application. However, precious (and base) metals biorefined from wastes may be useful for making cheap, low-grade catalysts for clean energy production. The concept of bionanomaterials for energy applications is reviewed with respect to potential fuel cell applications, bio-catalytic upgrading of oils and manufacturing 'drop-in fuel' precursors. Cheap, effective biomaterials would facilitate progress towards dual development goals of sustainable consumption and production patterns and help to ensure access to affordable, reliable, sustainable and modern energy.