Ecotoxicity of silver nanoparticles on estuarine and coastal bacterial communities

The increasing use of silver nanoparticles (AgNPs) as a biocidal agent and their potential accumulation in coastal environments may threaten non-target natural environmental bacterial communities. For this reason the main aim of this PhD project was to examine the effects of AgNPs on the functioning of natural bacterial assemblages that inhabit estuaries and coastal areas including the mechanisms behind the recovery and resistance to AgNPs. The susceptibility of pure bacterial cultures to three different AgNP types, two standard reference materials (Sigma Aldrich AgNPs and the Organisation for Economic Co-operation and Development (OECD) NM-300 AgNPs) and a cleaning product purchased from Mesosilver containing AgNPs was examined. The Mesosilver AgNPs product exhibited the highest antibacterial activity followed by the NM-300 AgNPs. The higher toxicity exhibited by the Mesosilver AgNPs was associated with their smaller particle size and initially higher concentration of silver in ionic form. For all the AgNPs types tested, the toxicity was bacterial species-specific, Gram negative bacteria being more resistant than the Gram positive species. This initial work informed the design of the microcosm experiments established with sediments and water samples collected from the estuary to develop the exposure to AgNPs under more realistic environmental conditions. The results showed that a single pulse of NM-300 AgNPs (1 mg L-1) that led to sediment concentrations below 6 mg Ag kg dry weight-1 decreased the bacterial carbon utilization rate of environmentally relevant carbon substrates. Following a 24 hr exposure the functional diversity changed, but recovered after 120 hr. This recovery may be explained by a number of possible factors, such as the formation of compounds less toxic than AgNPs, or by the complexation of AgNPs with natural organic matter and sediments reducing their bioavailability, or also due to the presence of silver resistance genes or groups of organisms more resistant to silver. AgNPs did not affect the bacterial community structure based on the phospholipid fatty acids (PLFAs) analysis. The microcosm experiments suggested that AgNPs under environmentally relevant conditions can negatively affect bacterial function and provides an insight into the understanding of the bacterial community response and resilience to AgNPs. The results of this research project have improved the current knowledge about the toxicity of different silver nanoparticles and the bacterial response under more realistic environmental conditions and will support future risk assessments and regulation process of products containing silver nanoparticles

Bacterial diversity associated with the Coccolithophorid Algae Emiliania huxleyi and Coccolithus pelagicus f. braarudii

Coccolithophores are unicellular calcifying marine phytoplankton that can form large and conspicuous blooms in the oceans and make significant contributions to oceanic carbon cycling and atmospheric CO2 regulation. Despite their importance, the bacterial diversity associated with these algae has not been explored for ecological or biotechnological reasons. Bacterial membership of Emiliania huxleyi and Coccolithus pelagicus f. braarudii cultures was assessed using cultivation and cultivation-independent methods. The communities were species rich compared to other phytoplankton cultures. Community analysis identified specific taxa which cooccur in all cultures (Marinobacter and Marivita). Hydrocarbon-degrading bacteria were found in all cultures. The presence of Acidobacteria, Acidimicrobidae, Schlegelella, and Thermomonas was unprecedented but were potentially explained by calcification associated with coccolith production. One strain of Acidobacteria was cultivated and is closely related to a marine Acidobacteria isolated from a sponge. From this assessment of the bacterial diversity of coccolithophores, a number of biotechnological opportunities are evident, from bioprospecting for novel taxa such as Acidobacteria to helping understand the relationship between obligate hydrocarbonoclastic bacteria occurrence with phytoplankton and to revealing bacterial taxa that have a specific association with algae and may be suitable candidates as a means to improve the efficiency of mass algal cultivation

Selective bacterial separation of critical metals:Towards a sustainable method for recycling lithium ion batteries

The large scale recycling of lithium ion batteries (LIBs) is essential to satisfy global demands for the raw materials required to implement this technology as part of a clean energy strategy. However, despite what is rapidly becoming a critical need, an efficient and sustainable recycling process for LIBs has yet to be developed. Biological reactions occur with great selectivity under mild conditions, offering new avenues for the implementation of more environmentally sustainable processes. Here, we demonstrate a sequential process employing two bacterial species to recover Mn, Co and Ni, from vehicular LIBs through the biosynthesis of metallic nanoparticles, whilst Li remains within the leachate. Moreover the feasibility of Mn recovery from polymetallic solutions was demonstrated at semi-pilot scale in a 30 L bioreactor. Additionally, to provide insight into the biological process occurring, we investigated selectivity between Co and Ni using proteomics to identify the biological response and confirm the potential of a bio-based method to separate these two essential metals. Our approach determines the principles and first steps of a practical bio-separation and recovery system, underlining the relevance of harnessing biological specificity for recycling and up-cycling critical materials

Roadmap for a sustainable circular economy in lithium-ion and future battery technologies

The market dynamics, and their impact on a future circular economy for lithium-ion batteries (LIB), are presented in this roadmap, with safety as an integral consideration throughout the life cycle. At the point of end-of-life (EOL), there is a range of potential options—remanufacturing, reuse and recycling. Diagnostics play a significant role in evaluating the state-of-health and condition of batteries, and improvements to diagnostic techniques are evaluated. At present, manual disassembly dominates EOL disposal, however, given the volumes of future batteries that are to be anticipated, automated approaches to the dismantling of EOL battery packs will be key. The first stage in recycling after the removal of the cells is the initial cell-breaking or opening step. Approaches to this are reviewed, contrasting shredding and cell disassembly as two alternative approaches. Design for recycling is one approach that could assist in easier disassembly of cells, and new approaches to cell design that could enable the circular economy of LIBs are reviewed. After disassembly, subsequent separation of the black mass is performed before further concentration of components. There are a plethora of alternative approaches for recovering materials; this roadmap sets out the future directions for a range of approaches including pyrometallurgy, hydrometallurgy, short-loop, direct, and the biological recovery of LIB materials. Furthermore, anode, lithium, electrolyte, binder and plastics recovery are considered in order to maximise the proportion of materials recovered, minimise waste and point the way towards zero-waste recycling. The life-cycle implications of a circular economy are discussed considering the overall system of LIB recycling, and also directly investigating the different recycling methods. The legal and regulatory perspectives are also considered. Finally, with a view to the future, approaches for next-generation battery chemistries and recycling are evaluated, identifying gaps for research. This review takes the form of a series of short reviews, with each section written independently by a diverse international authorship of experts on the topic. Collectively, these reviews form a comprehensive picture of the current state of the art in LIB recycling, and how these technologies are expected to develop in the future

Characterisation of enzymatic processing of commercial (Kraft) lignin by high resolution FT-ICR mass spectrometry - Dataset.

High Resolution FT-ICR mass spectrometry datasets analysing the enzymatic processing of Kraft lignin.Echavarri-Bravo, Virginia; Tinzl, Matthias; Cruickshank, Faye; Mackay, C Logan; Clarke, David. (2018). Characterisation of enzymatic processing of commercial (Kraft) lignin by high resolution FT-ICR mass spectrometry - Dataset., [dataset]. University of Edinburgh, School of Chemistry. https://doi.org/10.7488/ds/2459

Selective bacterial separation of critical metals: a sustainable method for recycling lithium ion batteries

The large scale recycling of lithium ion batteries (LIBs) is essential to satisfy global demands for the raw materials required to implement this technology as part of a clean energy strategy. However, despite what is rapidly becoming a critical need, an efficient and sustainable recycling process for LIBs has yet to be developed. Biological reactions occur with great selectivity under mild conditions, offering new avenues for the implementation of more environmentally sustainable processes. Here, we demonstrate a sequential process employing two bacterial species to recover Mn, Co and Ni, from vehicular LIBs through the biosynthesis of metallic nanoparticles, whilst Li remains within the leachate. We investigated bio-selectivity between Co and Ni using proteomics, confirming control of the biological response. Our approach determines the principles and first steps of a practical bio-separation and recovery system, underlining the relevance of harnessing biological specificity for recycling and up-cycling critical material