Development of a Constructed Wetland Water Treatment System for Selenium Removal: Incorporation of an Algal Treatment Component

Huang, Jung-Chen; Suárez, María C.; Yang, Soo In; Lin, Zhi-Qing; Terry, Norman

doi:10.1021/es4015629

Cited by 16 publications

(18 citation statements)

References 37 publications

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“…The inclusion of an algal pretreatment unit into a constructed wetland system was investigated in order to remove Se from river water entering the Salton Sea in California. The alga Chlorella vulgaris removed 96% of Se supplied as selenium oxyanions (1.58 mg liter Ϫ1 ) from the microcosm water column within 72 h. With this arrangement, up to 61% of the selenium was removed by volatilization to the atmosphere, suggesting that an algal pretreatment stage can be included for selenium bioremediation into constructed wetland systems (108).…”

Section: Selenium Bioremediationmentioning

confidence: 96%

Microbial Transformations of Selenium Species of Relevance to Bioremediation

Eswayah

Smith

Gardiner

2016

Appl Environ Microbiol

180

102

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b Selenium species, particularly the oxyanions selenite (SeO 3 2؊ ) and selenate (SeO 4 2؊ ), are significant pollutants in the environment that leach from rocks and are released by anthropogenic activities. Selenium is also an essential micronutrient for organisms across the tree of life, including microorganisms and human beings, particularly because of its presence in the 21st genetically encoded amino acid, selenocysteine. Environmental microorganisms are known to be capable of a range of transformations of selenium species, including reduction, methylation, oxidation, and demethylation. Assimilatory reduction of selenium species is necessary for the synthesis of selenoproteins. Dissimilatory reduction of selenate is known to support the anaerobic respiration of a number of microorganisms, and the dissimilatory reduction of soluble selenate and selenite to nanoparticulate elemental selenium greatly reduces the toxicity and bioavailability of selenium and has a major role in bioremediation and potentially in the production of selenium nanospheres for technological applications. Also, microbial methylation after reduction of Se oxyanions is another potentially effective detoxification process if limitations with low reaction rates and capture of the volatile methylated selenium species can be overcome. This review discusses microbial transformations of different forms of Se in an environmental context, with special emphasis on bioremediation of Se pollution. Since the discovery in 1954 by Pinsent that the oxidation of formate by cell suspensions of Escherichia coli requires growth medium containing molybdate and selenite, there has been a growing interest in the biochemical role of selenium in microorganisms (1). Se is an essential component of selenoamino acids, such as selenomethionine and selenocysteine (the 21st proteinogenic amino acid), that occur in certain types of prokaryotic enzymes. Indeed, the requirement for selenite in E. coli growing on formate is linked to the fact that formate dehydrogenase contains selenocysteine. Other prokaryotic enzymes that contain selenocysteine include glycine reductase in several clostridia, formate dehydrogenases in diverse prokaryotes, including Salmonella, Clostridium, and Methanococcus, as well as hydrogenases in Methanococcus and other anaerobes. In addition, other bacterial Se-dependent enzymes, in which the selenium is part of the active site molybdenum-containing cofactor, include nicotinic acid dehydrogenase and xanthine dehydrogenase, which is present in certain clostridial species (2-4).Reactions that are involved in the cycling of Se in soil, including those influenced by microbes, are diagrammatically summarized in Fig. 1 2Ϫ and was spatially separated from sulfate reduction in the environment despite the presence of substantial concentrations of sulfate where it occurred. Thus, it can be concluded that Se and S have different reductive biogeochemical cycles and appear to involve distinct populations of microorganisms.With respect to the remediation of sel...

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Section: Selenium Bioremediationmentioning

confidence: 96%

Microbial Transformations of Selenium Species of Relevance to Bioremediation

Eswayah

Smith

Gardiner

2016

Appl Environ Microbiol

180

102

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“…The lack of reliable quantitative data on biomethylation for most natural (Se-depleted) systems stems from the fact that, historically, experiments focused on applying volatilization for the bioremediation of Se-contaminated soils and sediments or wastewaters concentrated on Se or simply focused on amending laboratory microcosms with Se to simulate the latter ( 16 – 23 ). Therefore, most studies of Se volatilization were performed using Se concentrations 10 3 - to 10 6 -fold higher than those commonly found in aqueous environmental media in the nanogram-per-liter to microgram-per-liter range.…”

Section: Introductionmentioning

confidence: 99%

Sulfur Amino Acid Status Controls Selenium Methylation in Pseudomonas tolaasii: Identification of a Novel Metabolite from Promiscuous Enzyme Reactions

Liu

Hedwig

Schäffer

et al. 2021

Appl Environ Microbiol

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Selenium (Se) deficiency affects many millions of people worldwide, and the volatilization of methylated Se species to the atmosphere may prevent Se from entering the food chain. Despite the extent of Se deficiency, little is known about fluxes in volatile Se species and their temporal and spatial variation in the environment, giving rise to uncertainty in atmospheric transport models. To systematically determine fluxes, one can rely on laboratory microcosm experiments to quantify Se volatilization in different conditions. Here, it is demonstrated that the sulfur (S) status of bacteria crucially determines the amount of Se volatilized. Solid phase microextraction gas chromatography mass spectrometry showed that Pseudomonas tolaasii efficiently and rapidly (92% in 18h) volatilized Se to dimethyldiselenide and dimethylselenylsulfide through promiscuous enzymatic reactions with the S metabolism. However, when the cells were supplemented with cystine (but not methionine), a major proportion of the Se (∼48%) was channelled to thus far unknown, non-volatile Se compounds at the expense of the previously formed dimethyldiselenide and dimethylselenylsulfide (accounting for < 4% of total Se). Ion chromatography and solid phase extraction were used to isolate unknowns, and electrospray ionization ion trap mass spectrometry, electrospray ionization quadrupole time-of-flight mass spectrometry and microprobe nuclear magnetic resonance spectrometry were used to identify the major unknown as a novel Se metabolite, 2-hydroxy-3-(methylselanyl)propanoic acid. Environmental S concentrations often exceed Se concentrations by orders of magnitude. This suggests that in fact S status may be a major control on selenium fluxes to the atmosphere. Importance Volatilization from soil to the atmosphere is a major driver for Se deficiency. "Bottom up" models for atmospheric Se transport are based on laboratory experiments quantifying volatile Se compounds. The high Se and low S concentrations in such studies poorly represent the environment. Here, we show that S amino acid status has in fact a decisive effect on the production of volatile Se species in Pseudomonas tolaasii. When the strain was supplemented with S amino acids, a major proportion of the Se was channelled to thus far unknown, non-volatile Se compounds at the expense of volatile compounds. This hierarchical control of the microbial S amino acid status on Se cycling has been thus far neglected. Understanding these interactions – if occurring in the environment- will help to improve atmospheric Se models and thus predict drivers of Se deficiency.

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“…Algae and cyanobacteria are reported to provoke resistance to a variety of metal and transition metal oxyanions, including Se (Huang et al, 2013;Dixit and Singh, 2014). The resistance is attributed to the capacity of these organisms to modify their antioxidative machinery in response to toxic ROS generated under stressful condition which in turn can damage the cellular compartments.…”

Section: Introductionmentioning

confidence: 99%