Energy storage using batteries offers a solution to the intermittent nature of energy production from renewable sources; however, such technology must be sustainable. This Review discusses battery development from a sustainability perspective, considering the energy and environmental costs of state-of-the-art Li-ion batteries and the design of new systems beyond Li-ion. Images: batteries, car, globe: © iStock/Thinkstock.

Towards greener and more sustainable batteries for electrical energy storage

Metallurgical recovery of metals from electronic waste: a review.

Bioleaching of metal sulfides is caused by astonishingly diverse groups of bacteria. Today, at least 11 putative prokaryotic divisions can be related to this phenomenon. In contrast, the dissolution (bio)chemistry of metal sulfides follows only two pathways, which are determined by the acid-solubility of the sulfides: the thiosulfate and the polysulfide pathway. The bacterial cell can effect this sulfide dissolution by “contact” and “non-contact” mechanisms. The non-contact mechanism assumes that the bacteria oxidize only dissolved iron(II) ions to iron(III) ions. The latter can then attack metal sulfides and be reduced to iron(II) ions. The contact mechanism requires attachment of bacteria to the sulfide surface. The primary mechanism for attachment to pyrite is electrostatic in nature. In the case of Acidithiobacillus ferrooxidans, bacterial exopolymers contain iron(III) ions, each complexed by two uronic acid residues. The resulting positive charge allows attachment to the negatively charged pyrite. Thus, the first function of complexed iron(III) ions in the contact mechanism is mediation of cell attachment, while their second function is oxidative dissolution of the metal sulfide, similar to the role of free iron(III) ions in the non-contact mechanism. In both cases, the electrons extracted from the metal sulfide reduce molecular oxygen via a complex redox chain located below the outer membrane, the periplasmic space, and the cytoplasmic membrane of leaching bacteria. The dominance of either At. ferrooxidans or Leptospirillum ferrooxidans in mesophilic leaching habitats is highly likely to result from differences in their biochemical iron(II) oxidation pathways, especially the involvement of rusticyanin.

Bioleaching review part A: progress in bioleaching: fundamentals and mechanisms of bacterial metal sulfide oxidation.

Extracellular polymeric substances (EPS) produced by microorganisms are a complex mixture of biopolymers primarily consisting of polysaccharides, as well as proteins, nucleic acids, lipids and humic substances. EPS make up the intercellular space of microbial aggregates and form the structure and architecture of the biofilm matrix. The key functions of EPS comprise the mediation of the initial attachment of cells to different substrata and protection against environmental stress and dehydration. The aim of this review is to present a summary of the current status of the research into the role of EPS in bacterial attachment followed by biofilm formation. The latter has a profound impact on an array of biomedical, biotechnology and industrial fields including pharmaceutical and surgical applications, food engineering, bioremediation and biohydrometallurgy. The diverse structural variations of EPS produced by bacteria of different taxonomic lineages, together with examples of biotechnological applications, are discussed. Finally, a range of novel techniques that can be used in studies involving biofilm-specific polysaccharides is discussed.

https://www.mdpi.com/1420-3049/14/7/2535/pdf

Bacterial extracellular polysaccharides involved in biofilm formation.

The bioleaching of sulphide minerals with emphasis on copper sulphides — A review

Bioleaching - a result of interfacial processes caused by extracellular polymeric substances (EPS).

Extracellular polymeric substances seem to play a pivotal role in bioleaching for the winning of precious metals as well as acid rock drainage. For better control of both processes, the structure and function of extracellular polymeric substances from leaching bacteria are of crucial importance. The research focussed on Acidithiobacillus ferrooxidans, the compn. of its extracellular polymeric substances and further deduction of their function. The extracellular polymeric substances of Acidithiobacillus ferrooxidans consist mainly of neutral sugars and lipids. The functions of the extracellular polymeric substances of this leaching bacterium seem to be to (1) mediate attachment to a metal sulfide surface (2) conc. iron(III) ions by complexation through uronic acids or other residues at the mineral surface and, thus, allowing for an oxidative attack on the sulfide. The consequence is the enhancement of metal sulfide, dissoln. which may result in an acceleration of 20-100 fold over that of chem. leaching. Expts. were performed to elucidate the importance of the iron(III)ions complexed by extracellular polymeric substances for strain specific differences in oxidative activity for pyrite dissoln. The strains of Acidithiobacillus ferrooxidans with a high amt. of iron(III) ions in their extracellular polymeric substances possess a higher oxidn. activity than those with less iron(III) ions. These data provide insight into the function and consequently the advantage extracellular polymeric substances confer to bacteria involved in bioleaching.

K. Kinzler

Papers

Bioleaching review part A: progress in bioleaching: fundamentals and mechanisms of bacterial metal sulfide oxidation.

Bioleaching - a result of interfacial processes caused by extracellular polymeric substances (EPS).

Bioleaching - a result of interfacial processes caused by extracellular polymeric substances (EPS).

The EPS of Acidithiobacillus ferrooxidans--a model for structure-function relationships of attached bacteria and their physiology.