Metagenomic- and Cultivation-Based Exploration of Anaerobic Chloroform Biotransformation in Hypersaline Sediments as Natural Source of Chloromethanes

Chloroform (CF) is an environmental contaminant that can be naturally formed in various environments ranging from forest soils to salt lakes. Here we investigated CF removal potential in sediments obtained from hypersaline lakes in Western Australia. Reductive dechlorination of CF to dichloromethane (DCM) was observed in enrichment cultures derived from sediments of Lake Strawbridge, which has been reported as a natural source of CF. No CF removal was observed in abiotic control cultures without artificial electron donors, indicating biotic CF dechlorination in the enrichment cultures. Increasing vitamin B12 concentration from 0.04 to 4 µM in enrichment cultures enhanced CF removal and reduced DCM formation. In cultures amended with 4 µM vitamin B12 and 13C labelled CF, formation of 13CO2 was detected. Known organohalide-respiring bacteria and reductive dehalogenase genes were neither detected using quantitative PCR nor metagenomic analysis of the enrichment cultures. Rather, members of the order Clostridiales, known to co-metabolically transform CF to DCM and CO2, were detected. Accordingly, metagenome-assembled genomes of Clostridiales encoded enzymatic repertoires for the Wood-Ljungdahl pathway and cobalamin biosynthesis, which are known to be involved in fortuitous and nonspecific CF transformation. This study indicates that hypersaline lake microbiomes may act as a filter to reduce CF emission to the atmosphere.

Prospective (Bio)leaching of Historical Copper Slags as an Alternative to Their Disposal

The aim of this study was to evaluate the feasibility of (bio)hydrometallurgical methods for metal extraction from historical copper slags. Two types of slags (amorphous slag—AS, and crystalline slag—CS) were subjected to 24 to 48 h of leaching with: (i) Sulfuric acid at 0.1, 0.5, and 1 M concentrations at 1%, 5%, and 10% pulp densities (PDs); and (ii) normality equivalent (2 N) acids (sulfuric, hydrochloric, nitric, citric, and oxalic) at pulp densities ranging from 1% to 2%. Bioleaching experiments were performed within 21 days with Acidithiobacillus thiooxidans accompanied by an abiotic control (sterile growth medium). The results demonstrated that the most efficient treatment for amorphous and crystalline slag was bioleaching at 1% PD over 21 days, which led to extraction of Cu at rates of 98.7% and 52.1% for AS and CS, respectively. Among the chemical agents, hydrochloric acid was the most efficient and enabled 30.5% of Cu to be extracted from CS (1% PD, 48 h) and 98.8% of Cu to be extracted from AS (1% PD, 24 h). Slag residues after leaching were characterized by strong alteration features demonstrated by the complete dissolution of fayalite in the case of CS and the transformation of AS to amorphous silica and secondary gypsum. Based on this study, we conclude that amorphous slag is a more suitable candidate for potential metal recovery because of its generally high susceptibility to leaching and due to the generation of residue significantly depleted in metals as the end product. The inventory of economically relevant metals showed that 1 ton of historical copper slag contains metals valued at $47 and $135 for crystalline and amorphous slag, respectively, suggesting that secondary processing of such materials can potentially be both economically and environmentally viable.

Recycling of Florescent Phosphor Powder Y2O3:Eu by Leaching Experiments

Due to the advancing development of new technologies and consumer goods the future demand for raw materials will rise significantly. The finite primary raw materials will not be able to meet the demand quickly enough or the prices for the extraction will rise enormously. In consequence, a recycling of process waste and end of life products will be in future an essential step in order to meet the demand. Y2O3:Eu fluorescent phosphor was identified as the main composition in phosphor waste fractions and was chemical leached and bioleached with A. ferrooxidans. A selective leaching towards Y in bioleaching batches was observed and already after four days 100 % could be leached. The bioleaching with the bacteria showed no significant differences in comparison to the abiotic control without microorganism. Initial Fe3+ in the medium was identified as the driving force and lower extraction efficiencies of the biotic batches were attributed to a biosorption process and to high pH-values. This work showed that the extraction of yttrium out of waste products with high Y2O3:Eu content by chemical leaching with Fe-addition under mild conditions offers a good perspective to support the material demand of Y in the future growing market. In comparison to bioleaching of other fluorescent phosphors and waste fractions leaching efficiencies up to 100% were achieved and it was identified that the microorganisms can positively influence the leaching effect. Furthermore, it became obvious that the leaching behavior of microorganisms was highly dependent on the sample material. As relevant parameters mainly the structural composition of the phosphor was identified.

Ecosystem Composition Controls the Early Fate of Rare Earth Elements during Incipient Soil Genesis

The rare earth elements (REE) are of increasing importance in a variety of science and economic fields, including (bio)geosciences, paleoecology, astrobiology, and mining. Despite their great promise, REE fractionation in early plant-microbe-rock systems has largely remained elusive. We tested the hypothesis that REE mass-partitioning during the incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, plant, and arbuscular mycorrhiza. Pore-water element abundances reflected a rapid transition from abiotic to biotic weathering, the latter associated with lower aqueous loss and higher uptake. Abiotic dissolution contributed 38.6+/-19% to total denudation. Microbes incremented denudation, particularly in rhyolite, this effect associating with decreased bioavailable solid fractions in this rock. Total mobilization (aqueous+uptake) was ten times greater in planted treatments compared to abiotic control, REE masses in plant generally exceeding those in water. Plants of larger biomass further increased solid fractions, consistent with soil genesis. Mycorrhiza had a generally positive effect on total mobilization. The incipient REE weathering was dominated by inorganic dissolution enhanced by biotic respiration, the patterns of denudation largely dictated by mineralogy. A consistent biotic signature was observed in La:phosphate, mobilization:solid fraction in all rocks, as well as in the general pattern of denudation and uptake.

Presence and persistence of wastewater pathogen Escherichia coli O157:H7 in hydroponic reactors of treatment wetland species

Treatment wetlands (TWs) efficiently remove many pollutants including a several log order reduction of pathogens from influent to effluent; however, there is evidence to suggest that pathogen cells are sequestered in a subsurface wetland and may remain viable months after inoculation. Escherichia coli is a common pathogen in domestic and agricultural wastewater and the O157:H7 strain causes most environmental outbreaks in the United States. To assess attachment of E. coli to the TW rhizosphere, direct measurements of E. coli levels were taken. Experiments were performed in chemostats containing either Teflon nylon as an abiotic control or roots of Carex utriculata or Schoenoplectus acutus. Flow of simulated wastewater through the chemostat was set to maintain a 2 hour residence time. The influent was inoculated with E. coli O157:H7 containing DsRed fluorescent protein. Root samples were excised and analyzed via epifluorescent microscopy. E. coli O157:H7 was detected on the root surface at 2 hours after inoculation, and were visible as single cells. Microcolonies began forming at 24 hours post-inoculation and were detected for up to 1 week post-inoculation. Image analysis determined that the number of microcolonies with >100 cells increased 1 week post-inoculation, confirming that E. coli O157:H7 is capable of growth within biofilms surrounding wetland plant roots.

Solid electron acceptor effect on biocatalyst activity in treating azo dye based wastewater

Schematic representation of (a) BET, (b) AnT and (c) abiotic-control operations along with the electron flux mechanism occurring in presence and absence of electrode assembly.