Electro-extractive fermentation for efficient biohydrogen production

Electrodialysis, an electrochemical membrane technique, was found to prolong and enhance the production of biohydrogen and purified organic acids via the anaerobic fermentation of glucose by Escherichia coli. Through the design of a model electrodialysis medium using cationic buffer, pH was precisely controlled electrokinetically, i.e. by the regulated extraction of acidic products with coulombic efficiencies of organic acid recovery in the range 50–70% maintained over continuous 30-day experiments. Contrary to\ud previous reports, E. coli produced H2 after aerobic growth in minimal medium without inducers and with a mixture of organic acids dominated by butyrate. The selective separation of organic acids from fermentation provides a potential nitrogen-free carbon source for further biohydrogen production in a parallel photofermentation. A parallel study incorporated this fermentation system into an integrated biohydrogen refinery (IBR) for the conversion of organic waste to hydrogen and energy

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

EPSRC (EP/I007806/1; EP/D05768X/1), BBSRC (BB/ C516128/1), NERC (NE/L014076/1), The Royal Society (Industrial Fellowship) and Spanish Government Sistema Nacional de Garantia Juvenil grant PEJ-2014-P-00391.This work was supported by EPSRC (grants No EP/ I007806/1 and EP/D05768X/1), BBSRC (grant No BB/ C516128/1), NERC (grant NE/L014076/1) and by a Royal Society Industrial Fellowship to LEM for secondment into C-Tech Innovation Ltd., who provided the bespoke apparatus used in this work. We acknowledge the invaluable contributions of the late Dr Ruth Wroe of C-Tech Innovation Ltd. into useful discussions and the kind permission of Drs S. Megit, C. Berry and A. Morby (University of Cardiff, UK) to show their unpublished work in Supplementary Information. This work was partially supported by the Spanish Government Sistema Nacional de Garantia Juvenil Grant PEJ-2014-P- 00391 (Promocion de Empleo Joven e Implantacion de la Garantia Juvenil 2014, MINECO) with a scholarship to JGB. We also thank the EM Centre at U. Granada for access to high-resolution electron microscopy (in Fig. S2 and S3). All authors declare no competing interests.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 (mu mol 2-pentyne converted s(-1)) was increased by similar to 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.UK Research & Innovation (UKRI) Engineering & Physical Sciences Research Council (EPSRC) EP/I007806/1 EP/D05768X/1UK Research & Innovation (UKRI) Biotechnology and Biological Sciences Research Council (BBSRC) BB/C516128/1UK Research & Innovation (UKRI)Natural Environment Research Council (NERC) NE/L014076/1Royal Society of London European CommissionSpanish Government Sistema Nacional de Garantia Juvenil grant PEJ-2014-P-0039

Biosynthesis of zinc sulfide quantum dots using waste off-gas from a metal bioremediation process

Waste H2S biogas from a mine-water remediation bioprocess is used to make zinc sulfide quantum dots which are identical to ZnS QDs made by chemical methods.</p

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

The authors acknowledge with thanks, use of GC-FID/GC-MS supplied by Dr. Daniel Lester within the Polymer Characterization Research Technology Platform, University of Warwick and the help of Drs. B. Kaulich, T. Araki,and M. Kazemian at beamline IO8, Diamond Light Source, United Kingdom, who funded the synchrotron study (Award No. SP16407: Scanning X-ray Microscopy Study of Biogenic Nanoparticles; Improved Bionanocatalysts by Design) on I08 Scanning X-ray Microscopy beamline (SXM).The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2019.00970/full#supplementary-materialBiogas-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.This project was funded by NERC grant NE/L014076/1 to LM (Program: “Resource Recovery from Wastes”). The Science City Photoemission Facility used in this research was funded through the Science Cities Advanced Materials Project 1: “Creating and Characterizing Next Generation of Advanced Materials” with support from AWM and ERDF funds. The microscopy work was conducted at “Centro de Instrumentación Cientifica” at the University of Granada, Spain. This work was partially supported by the Spanish Government Sistema Nacional de Grantia Juvenil grant PEJ-2014-P-00391 (Promocion de Empleo Joven e Implantacion de la Garantia Juvenil 2014, MINECO) with a scholarship to JGB

Biomanufacture of nano-Pd(0) by Escherichia coli and electrochemical activity of bio-Pd(0) made at the expense of H2 and formate as electron donors

Objective: Palladised cells of Desulfovibrio desulfuricans and Shewanella oneidensis have been reported as fuel cell electrocatalysts but growth at scale may be unattractive/costly; we have evaluated the potential of using E. coli, using H2/formate for Pd-nanoparticle manufacture. Results: Using ‘bio-Pd’ made under H2 (20 wt%) cyclic voltammograms suggested electrochemical activity of bio-NPs in a native state, attributed to proton adsorption/desorption. Bio-Pd prepared using formate as the electron donor gave smaller, well separated NPs; this material showed no electrochemical properties, and hence little potential for fuel cell use using a simple preparation technique. Bio-Pd on S. oneidensis gave similar results to those obtained using E. coli. Conclusion: Bio-Pd is sufficiently conductive to make an E. coli-derived electrochemically active material on intact, unprocessed bacterial cells if prepared at the expense of H2, showing potential for fuel cell applications using a simple one-step preparation method

Microbial synthesis of core/shell gold/palladium nanoparticles for applications in green chemistry

We report a novel biochemical method based on the sacrificial hydrogen strategy to synthesize bimetallic gold (Au)–palladium (Pd) nanoparticles (NPs) with a core/shell configuration. The ability of Escherichia coli cells supplied with H2 as electron donor to rapidly precipitate Pd(II) ions from solution is used to promote the reduction of soluble Au(III). Pre-coating cells with Pd(0) (bioPd) dramatically accelerated Au(III) reduction, with the Au(III) reduction rate being dependent upon the initial Pd loading by mass on the cells. Following Au(III) addition, the bioPd–Au(III) mixture rapidly turned purple, indicating the formation of colloidal gold. Mapping of bio-NPs by energy dispersive X-ray microanalysis suggested Au-dense core regions and peripheral Pd but only Au was detected by X-ray diffraction (XRD) analysis. However, surface analysis of cleaned NPs by cyclic voltammetry revealed large Pd surface sites, suggesting, since XRD shows no crystalline Pd component, that layers of Pd atoms surround Au NPs. Characterization of the bimetallic particles using X-ray absorption spectroscopy confirmed the existence of Au-rich core and Pd-rich shell type bimetallic biogenic NPs. These showed comparable catalytic activity to chemical counterparts with respect to the oxidation of benzyl alcohol, in air, and at a low temperature (90°C)