Marion Paterson-Beedle

Effect of nutrient limitation on biofilm formation and phosphatase activity of a Citrobacter sp.

A phosphatase-overproducing Citrobacter sp. (NCIMB 40259) was grown in an air-lift reactor in steady-state continuous culture under limitation of carbon, phosphorus or nitrogen. Substantial biofilm formation, and the highest phosphatase activity, were observed under lactose limitation. However, the total amount of biofilm wet biomass and the phosphatase specific activity were reduced in phosphorus- or nitrogen-limited cultures or when glucose was substituted for lactose as the limiting carbon source. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) showed differences in cell and biofilm morphology in relation to medium composition. Electron microscopy suggested that the differences in biofilm formation may relate to differential expression of fimbriae on the cell surface.

Uptake of Sr 2+ and Co 2+ into biogenic hydroxyapatite: implications for biomineral ion exchange synthesis

Biomineral hydroxyapatite (Bio-HAp) produced by Serratia sp. has the potential to be a suitable material for the remediation of metal contaminated waters and as a radionuclide waste storage material. Varying the Bio-HAp manufacturing method was found to influence hydroxyapatite (HAp) properties and consequently the uptake of Sr(2+) and Co(2+). All the Bio-HAp tested in this study were more efficient than the commercially available hydroxyapatite (Com-HAp) for Sr(2+) and Co(2+) uptake. For Bio-HAp the uptake for Sr(2+) and Co(2+) ranged from 24 to 39 and 29 to 78 mmol per 100 g, respectively. Whereas, the uptake of Sr(2+) and Co(2+) by Com-HAp ranged from 3 to 11 and 4 to 18 mmol per 100 g, respectively. Properties that increased metal uptake were smaller crystallite size (<40 nm) and higher surface area (>70 m(2) g(-1)). Organic content which influences the structure (e.g., crystallite arrangement, size and surface area) and composition of Bio-HAp was also found to be important in Sr(2+) and Co(2+) uptake. Overall, Bio-HAp shows promise for the remediation of aqueous metal waste especially since Bio-HAp can be synthesized for optimal metal uptake properties.

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.

Biomineralization: linking the fossil record to the production of high value functional materials

The microbial cell offers a highly efficient template for the formation of nanoparticles with interesting properties including high catalytic, magnetic and light-emitting activities. Thus biomineralization products are not only important in global biogeochemical cycles, but they also have considerable commercial potential, offering new methods for material synthesis that eliminate toxic organic solvents and minimize expensive high-temperature and pressure processing steps. In this review we describe a range of bacterial processes that can be harnessed to make precious metal catalysts from waste streams, ferrite spinels for biomedicine and catalysis, metal phosphates for environmental remediation and biomedical applications, and biogenic selenides for a range of optical devices. Recent molecular-scale studies have shown that the structure and properties of bionanominerals can be fine-tuned by subtle manipulations to the starting materials and to the genetic makeup of the cell. This review is dedicated to the late Terry Beveridge who contributed much to the field of biomineralization, and provided early models to rationalize the mechanisms of biomineral synthesis, including those of geological and commercial potential.

[20] Study of biofilm within a packed-bed reactor by theee-dimensional magnetic resonance imaging

Publisher Summary This chapter describes the 3D MRI technique used to acquire images. MRI technique discussed in this article has great potential for studies not only of biofilms immobilized onto supports, but also of the overall functioning of bioreactors. MRI can also be used to monitor systems over a period of time. This technique is sensitive to motion and to temperature and it can be used to measure quantitatively in three dimensions dynamic changes, such as flow, diffusion, and mass- and heat-transfer. Besides the obvious importance of such experimental data in their own right, such data have unique potential for validation of the computer software used to model bioreactor processes. The chapter also provides an overview of the underlying principles of MRI and of some of the limitations of the technique with respect to imaging of biofilms. Other applications of MRI that are relevant to the study of bioreactors are described.

Visualisation of metal deposition in biofilm reactors by three-dimensional magnetic resonance imaging (MRI)

Three-dimensional magnetic resonance imaging (MRI) was used to visualise polyurethane foam-immobilised Citrobacter after challenging with La3+ and/or Cu2+ in citrate buffer supplemented with glycerol 2-phosphate. Extensive phosphatase-mediated bioaccumulation of LaPO4 was observed but no evidence for deposition of Cu3(PO4)2 was obtained by X-ray diffraction and proton-induced X-ray emission analyses. Image analysis showed that La3+/Cu2+ is a good model system to study the function of this biofilm reactor non-invasively by MRI.

Radiotolerance of phosphatases of a Serratia sp.: potential for the use of this organism in the biomineralization of wastes containing radionuclides.

Aqueous wastes from nuclear fuel reprocessing present special problems of radiotoxicity of the active species. Cells of Serratia sp. were found previously to accumulate high levels of hydrogen uranyl phosphate (HUP) via the activity of a phosphatase enzyme. Uranium is of relatively low radiotoxicity whereas radionuclide fission products such as 90Sr and 137Cs are highly radiotoxic. These radionuclides can be co‐crystallized, held within the bio‐HUP “host” lattice on the bacterial cells and thereby removed from contaminated solution, depending on continued phosphatase activity. Radiostability tests using a commercial 60Co γ‐source showed that while cell viability and activity of purified phosphatase were lost within a few hours on irradiation, whole‐cell phosphatase retained 80% of the initial activity, even after loss of cell culturability, which was increased to 100% by the incorporation of mercaptoethanol as an example radioprotectant, beyond an accumulated dose of >1.3 MGy. Using this co‐crystallization approach (without mercaptoethanol) 137Cs+ and 85Sr2+ were removed from a simulated waste selectively against a 33‐fold excess of Na+. Biotechnol. Bioeng. 2012; 109:1937–1946.

Electron Paramagnetic Resonance Analysis of Active Bio-Pd-Based Electrodes for Fuel Cells

Nanoparticles of palladium were obtained with the help of hydrogen-oxidising, metal- reducing bacteria and used for the production of electricity in a proton exchange membrane (PEM) fuel cell. Earlier works have shown that palladised cells of Escherichia coli and Desulfovibrio desulfuricans (Bio-PdE.coli and Bio-PdD.desulfuricans, respectively) appeared similar by electron microscopy and were comparably active in a chemical test reaction. When tested in a PEM fuel cell they produced 0.018 and 0.108 W, respectively. Electron paramagnetic resonance analysis of Bio-PdE.coli mixed with activated carbon showed paramagnetic activity. However, Bio-PdD.desulfuricans under the same conditions quenched the intrinsic EPR signal. This quenching is indicative of the magnetic properties of the particles. The magnetic behaviour of Pd nanoparticles was theoretically predicted for particles between 10 and 20 nm in diameter and can be experimentally confirmed by EPR measurements.

6.55 – Today’s Wastes, Tomorrow’s Materials for Environmental Protection

Over the past 30 years, the literature has burgeoned with bioremediation approaches to heavy metal removal from wastes. The price of base and precious metals has also increased. With the resurgence of nuclear energy, uranium has become a strategic resource. Other noncarbon energy technologies are driven by the need to reduce CO2 emissions. The ‘new biohydrometallurgy’ we describe unites these drivers by the concept of conversion of wastes into new materials for environmental applications. The new materials, fashioned, bottom-up, into nanomaterials under biocontrol, can be termed ‘functional bionanomaterials’. This new discipline, encompassing waste treatment along with nanocatalysis or other applications, can be summarized as ‘environmental bionanotechnology’. Several case histories illustrate the scope and potential of this concept. The research highlights biogenic nuclear waste remediation, Pd and Pt bionanocatalysts for environment and energy, Au oxidation bionanocatalysts from jewelery waste, optically active bioproducts from Se oxyanions, and nanoscale magnets biofabricated from Fe (III) wastes.

Biorecovery of Uranium from Minewaters into Pure Mineral Product at the Expense of Plant Wastes

Perceived environmental problems of nuclear fuel fabrication, use and treatment limit the acceptability of nuclear power as an alternative to fossil fuels. This applies to nuclear fuel processing and reprocessing but contamination also occurs at source via run-offs from current and historic mining activities. The price of uranium (U3O8) in the1990s was US