Alachlor oxidation by the filamentous fungus Paecilomyces marquandii

Alachlor, a popular chloroacetanilide herbicide, can be a potential health risk factor. Soil microorganisms are primarily responsible for conversion and migration of alachlor in natural environment, but knowledge concerning alachlor biodegradation is not complete. Therefore, we studied the ability of Paecilomyces marquandii, soil fungus tolerant to heavy metals, to eliminate alachlor and proposed a new pathway of its transformation. After 7 days of incubation only 3.3% of alachlor was detected from an initial concentration 50 mg L-1 and 20.1% from a concentration 100 mg L-1. The qualitative IDA LC-MS analysis showed the presence of ten metabolites. All of them were dechlorinated mainly through oxidation, but also reductive dechlorination was observed. The main route of alachlor conversion progressed via N-acetyl oxidation resulting in the formation of mono-, di- and trihydroxylated byproducts. N-acetyl oxidation as a dominant route of alachlor metabolism by fungi has not been described so far. The toxicity of alachlor tested with Artemia franciscana did not increase after treatment with P. marquandii cultures. Paecilomyces marquandii strain seems to be an interesting model for the research on alachlor conversion by soil microscopic fungi, due to its dechlorination and hydroxylation ability as well as high tolerance to heavy metals.Grant of the National Centre for Science in Cracow, Poland, No UMO-2011/01/B/NZ9/0289

INNOVATIVE ECO-EFFICIENT BIOHYDROMETALLURGICAL PROCESSES FOR THE RECOVERY OF STRATEGIC AND RARE METALS FROM PRIMARY AND SECONDARY RESOURCES

The conventional pyrometallurgical route for winning of metals is increasingly confronted with a number of challenges which include the necessity to exploit more complex and deeper deposits, arsenic containing deposits, increased demands to protect the environment, and to use less energy. Biohydrometallurgical processes have been shown to be a good alternative for the winning of metals from poor and complex ores

Microbes at the extreme: mining with microbes

The use of microorganisms to recover precious and base metals from mineral ores and concentrates is called biomining, or biohydrometallurgical processing. Biomining occurs through the natural ability of certain microorganisms to catalyse reactions, leading to the solubilisation of metals from the minerals. This process is used today in commercial operations to recover copper, nickel, cobalt, zinc and uranium from complex ore

Interrelationship of hydrology, microbial colonisation and hydrometallurgy in a simulated chalcopyrite heap leach

Includes bibliographical references (leaves 104-115).Chalcopyrite is the most abundant primary copper sulphide mineral found worldwide. As copper grades of ores available for extraction decrease, heap bioleaching is gaining interest as a potential operating alternative to traditional methods of roasting and smelting. The efficiency by which bacteria assist leaching chalcopyrite is governed by their interaction and association to the sulphide mineral in the ore. While both planktonic and mineral-associated micro-organisms contribute to the bioleaching of mineral sulphides through the oxidation of ferrous iron little information exists as to their ability to adhere and leach low grade chalcopyrite ore. This study was undertaken to determine the association of defined and mixed microbial species on a chalcopyrite concentrate and a chalcopyrite ore. At. ferrooxidans, At. caldus, At. thiooxidans and L. ferrooxidans were grown in pure culture and used to investigate the mineral-microbe association within defined experimental parameters of two experimental operations

Gold recovery from sulphide minerals:a bioprocessing approach

Sometimes gold recovery  from its ores represents a challenge. This is due to fine dissemination and interlocking of the gold within the associated sulfide minerals. Many approaches were tried to solve this problem, they included roasting, oxidation in addition to bioprocessing. In thelast approach, application of bacteria enhances sulfidesbio-oxidation and consequently facilitates their leaching. Therefore, this paper aims at investigating gold biorecovery from Alhura area gold ore, located at Kingdom ofSaudi Arabia. Investigated parameters included Feed Size,mm; Dose of bacteria, ml ; Retention time, day; Steeringspeed, rpm; Bacteria nutrient addition rate, K  2SO4, kg/t; Bacteria nutrient addition rate, (NH  4)3PO4, kg/t. Statistical screening of these parameters showed that the most significant ones are: ore feed size, dose of bacteria and K2SO4 nutrition in addition to retention time. However at optimum conditions, (10 ml bacterial dose, 6 days retention time, and 6.5 Kg/t K 2SO4 as bacteria nutrient) a gold concentrate containing up to 107g/t gold from an ore containing 1.14g/t gold was obtained

Nitrate-Dependent Iron Oxidation: A Potential Mars Metabolism

This work considers the hypothetical viability of microbial nitrate-dependent Fe2+ oxidation (NDFO) for supporting simple life in the context of the early Mars environment. This draws on knowledge built up over several decades of remote and in situ observation, as well as recent discoveries that have shaped current understanding of early Mars. Our current understanding is that certain early martian environments fulfill several of the key requirements for microbes with NDFO metabolism. First, abundant Fe2+ has been identified on Mars and provides evidence of an accessible electron donor; evidence of anoxia suggests that abiotic Fe2+ oxidation by molecular oxygen would not have interfered and competed with microbial iron metabolism in these environments. Second, nitrate, which can be used by some iron oxidizing microorganisms as an electron acceptor, has also been confirmed in modern aeolian and ancient sediment deposits on Mars. In addition to redox substrates, reservoirs of both organic and inorganic carbon are available for biosynthesis, and geochemical evidence suggests that lacustrine systems during the hydrologically active Noachian period (4.1–3.7 Ga) match the circumneutral pH requirements of nitrate-dependent iron-oxidizing microorganisms. As well as potentially acting as a primary producer in early martian lakes and fluvial systems, the light-independent nature of NDFO suggests that such microbes could have persisted in sub-surface aquifers long after the desiccation of the surface, provided that adequate carbon and nitrates sources were prevalent. Traces of NDFO microorganisms may be preserved in the rock record by biomineralization and cellular encrustation in zones of high Fe2+ concentrations. These processes could produce morphological biosignatures, preserve distinctive Fe-isotope variation patterns, and enhance preservation of biological organic compounds. Such biosignatures could be detectable by future missions to Mars with appropriate instrumentation

Feasibility study on the microbial separation of iron from slime

Bio-mineral processing is the generic term that describes the processing of metal containing ores, concentrator tailings, newly mined run-of-the-mine (ROM) material, and intermediate to high-grade ores using (micro-) biological technology. The slime generated by the Tata Iron and Steel Company is becoming a major problem for the Company. Since, it contains a high quantity of Iron (around 56%), it can be recycled for the generation of Steel. Bioleaching comes to the rescue of such a problem. As it contains a high percentage of alumina and silica as its component, it can be treated as a non- sulphide system. Heterotrophic organisms can be used to leach out the alumina and silica. We have thus tried to see the feasibility of Bacillus to leach the slime and increase the Iron content in it. The conditions like pH, time and inoculum size have been optimized. The results showed that, there was a maximum recovery of iron (around 79%) in the slime and the optimum conditions at which this was obtained were at pH of 7, a time of 5 days and inoculum size of 20%

Bioleaching of copper- and zinc-bearing ore using consortia of indigenous iron-oxidizing bacteria

Indigenous iron-oxidizing bacteria were isolated on modified selective 9KFe(2+) medium from Baiyin copper mine stope, China. Three distinct acidophilic bacteria were isolated and identified by analyzing the sequences of 16S rRNA gene. Based on published sequences of 16S rRNA gene in the GenBank, a phylogenetic tree was constructed. The sequence of isolate WG101 showed 99% homology with Acidithiobacillus ferrooxidans strain AS2. Isolate WG102 exhibited 98% similarity with Leptospirillum ferriphilum strain YSK. Similarly, isolate WG103 showed 98% similarity with Leptospirillum ferrooxidans strain L15. Furthermore, the biotechnological potential of these isolates in consortia form was evaluated to recover copper and zinc from their ore. Under optimized conditions, 77.68 +/- 3.55% of copper and 70.58 +/- 3.77% of zinc were dissolved. During the bioleaching process, analytical study of pH and oxidation-reduction potential fluctuations were monitored that reflected efficient activity of the bacterial consortia. The FTIR analysis confirmed the variation in bands after treatment with consortia. The impact of consortia on iron speciation within bioleached ore was analyzed using Mossbauer spectroscopy and clear changes in iron speciation was reported. The use of indigenous bacterial consortia is more efficient compared to pure inoculum. This study provided the basic essential conditions for further upscaling bioleaching application for metal extraction.</p

Biooxidación de concentrados refractarios de oro con alto contenido de arsénico

La biooxidación es una tecnología alternativa para el aprovechamientode minerales tales como el cobre, oro, platay otros. Los minerales auríferos son en muchos casos refractariosa los tratamientos tradicionales, y requieren decondiciones tecnológicas drásticas, tales como la pirometalurgia.La biooxidación se presenta como una alternativalimpia frente a estas condiciones. Sin embargo, losmicroorganismos presentan ciertas dificultades de desarrollocuando se encuentran con elementos tóxicos talescomo el arsénico, por lo que el objetivo de este estudio fueestablecer las posibilidades de aplicar esta tecnología enminerales con alto contenido de arsénico. Se trabajó conun cultivo mixto: Acidithiobacillus ferrooxidans, Acidithiobacillusthiooxidans y Leptospirillum ferrooxidans realizandouna adaptación previa de los microorganismos al arsénicohasta 1.5%. En medio 9K modificado se incrementóla densidad de pulpa hasta establecer el 15% como laconcentración óptima. Finalmente las pruebas realizadasen un reactor de 12 litros en condiciones controladas demostraronque en un tiempo de 21 días se podría obtenerun 41.03% de solubilización de arsénico, con una productividadvolumétrica global de 29.31mg/L.h. Los resultadosalcanzados hacen pensar en la necesidad de realizar estudiosa nivel piloto para definir la factibilidad de aplicacióndel proceso de biooxidación con este tipo de mineral