Biomining of Rare Earth Elements from Phosphate Ores and Minerals

Rare earth elements (REEs) are important for establishing a technology based society, however are difficult to process. The use of biomining for the extraction of REEs minerals offers a benign alternative to conventional hydrometallurgical routes with more selective solubilisation of REEs over radionuclides. The use of phosphate solubilising microorganisms in the bioleaching of REEs was investigated to gain a better understanding of the leaching behaviour of individual REEs and the mechanism attributed to their mobilisation

Speciation of metals in contaminated sediments in the Kalmar County, Sweden

In response to the growing numbers of contaminated sites, concerns about proper management with reduced environmental footprints have been raised. In the present study, mining of highly contaminated sediments to recover valuable elements such as metals and nutrients is proposed as sustainable approach, both through enhancing resilience of ecosystems and remediation, beside probable turnovers. Thereby, in order to evaluate feasibility of metal recovery, fractionation of thirteen heavy and trace metals (Fe, Al, As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) in Oskarshamn harbor and Malmfjärden semi-enclosed bay surface sediments taken from five polluted locations in Kalmar County in southeast of Sweden was studied. The dissolution experiment by a modified BCR (Community Bureau of Reference, now SM&T) sequential extraction procedure (BCR-SEP) was used to determine the partitioning of elements. Oskarshamn and Malmfjärden sediments showed highest mobility for Zn and Cd, which can be leached out easily by small changes in environment conditions, whereas Al, Ba, and Hg in both sites, beside Cr and Fe in Malmfjärden exhibited high percentage in residual fraction. Moreover, total digestion results turn out that Oskarshamn in comparing to Malmfjärden sediments tended to result in larger contents of total extractable heavy metals (except Al), which is strongly attributed to factories, wastewater treatment plants, and ships traffic in Oskarshamn basin and diffusive sources in Malmfjärden. Despite the smaller magnitude of pollution in Malmfjärden relative to Oskarshamn, besides dredging and removal of sediments, in situ remediation techniques such as capping, using amendments and phytoremediation could be suggested. The results indicated that among different metals in the sediments, particularly in Oskarshamn, Cu and Pb followed by As, Cr and Ni can be considered for future sediment mining

Klebsiella aerogenes adhesion behaviour during biofilm formation on monazite

The adsorption behaviour of micro-organisms during the initial attachment stage of biofilm formation affects subsequent stages. The available area for attachment and the chemophysical properties of a surface affect microbial attachment performance. This study focused on the initial attachment behaviour of Klebsiella aerogenes on monazite by measuring the ratio of planktonic against sessile subpopulations (P:S ratio), and the potential role of extracellular DNA (eDNA). eDNA production, effects of physicochemical properties of the surface, particle size, total available area for attachment, and the initial inoculation size on the attachment behaviour were tested. K. aerogenes attached to monazite immediately after exposure to the ore; however, the P:S ratio significantly (p = 0.05) changed in response to the particle size, available area, and inoculation size. Attachment occurred preferentially on larger-sized (~50 µm) particles, and either decreasing the inoculation size or increasing the available area further promoted attachment. Nevertheless, a portion of the inoculated cells always remained in a planktonic state. K. aerogenes produced lower eDNA in response to the changed surface chemical properties when monazite was replaced by xenotime. Using pure eDNA to cover the monazite surface significantly (p ≤ 0.05) hindered bacterial attachment due to the repulsive interaction between the eDNA layer and bacteria

Unlocking survival mechanisms for metal and oxidative stress in the extremely acidophilic, halotolerant Acidihalobacter genus.

Microorganisms used for the biohydrometallurgical extraction of metals from minerals must be able to survive high levels of metal and oxidative stress found in bioleaching environments. The Acidihalobacter genus consists of four species of halotolerant, iron–sulfur-oxidizing acidophiles that are unique in their ability to tolerate chloride and acid stress while simultaneously bioleaching minerals. This paper uses bioinformatic tools to predict the genes and mechanisms used by Acidihalobacter members in their defense against a wide range of metals and oxidative stress. Analysis revealed the presence of multiple conserved mechanisms of metal tolerance. Ac. yilgarnensis F5T, the only member of this genus that oxidizes the mineral chalcopyrite, contained a 39.9 Kb gene cluster consisting of 40 genes encoding mobile elements and an array of proteins with direct functions in copper resistance. The analysis also revealed multiple strategies that the Acidihalobacter members can use to tolerate high levels of oxidative stress. Three of the Acidihalobacter genomes were found to contain genes encoding catalases, which are not common to acidophilic microorganisms. Of particular interest was a rubrerythrin genomic cluster containing genes that have a polyphyletic origin of stress-related functions

Biofilm formation on the surface of monazite and xenotime during bioleaching

Abstract Microbial attachment and biofilm formation is a ubiquitous behaviour of microorganisms and is the most crucial prerequisite of contact bioleaching. Monazite and xenotime are two commercially exploitable minerals containing rare earth elements (REEs). Bioleaching using phosphate solubilizing microorganisms is a green biotechnological approach for the extraction of REEs. In this study, microbial attachment and biofilm formation of Klebsiella aerogenes ATCC 13048 on the surface of these minerals were investigated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). In a batch culture system, K. aerogenes was able to attach and form biofilms on the surface of three phosphate minerals. The microscopy records showed three distinctive stages of biofilm development for K. aerogenes commencing with initial attachment to the surface occurring in the first minutes of microbial inoculation. This was followed by colonization of the surface and formation of a mature biofilm as the second distinguishable stage, with progression to dispersion as the final stage. The biofilm had a thin‐layer structure. The colonization and biofilm formation were localized toward physical surface imperfections such as cracks, pits, grooves and dents. In comparison to monazite and xenotime crystals, a higher proportion of the surface of the high‐grade monazite ore was covered by biofilm which could be due to its higher surface roughness. No selective attachment or colonization toward specific mineralogy or chemical composition of the minerals was detected. Finally, in contrast to abiotic leaching of control samples, microbial activity resulted in extensive microbial erosion on the high‐grade monazite ore