Microbial-Based Bioremediation of Selenium and Tellurium Compounds

Abstract

The chalcogens selenium (Se) and tellurium (Te) are rare earth elements, which are mainly present in the environment as toxic oxyanions, due to the anthropogenic activities. Thus, the increased presence of these chalcogen-species in the environment and the contamination of wastewaters nearby processing facilities led to the necessity in developing remediation strategies aimed to detoxify waters, soils and sediments. Among the different decontamination approaches, those based on the ability of microorganisms to bioaccumulate, biomethylate or bioconvert Se-and/or Te-oxyanions are considered the leading strategy for achieving a safe and eco-friendly bioremediation of polluted sites. Recently, several technologies based on the use of bacterial pure cultures, bacterial biofilms or microbial consortia grown in reactors with different configurations have been explored for Se-and Te-decontamination purposes. Further, the majority of microorganisms able to process chalcogen-oxyanions have been described to generate valuable Se-and/or Te-nanomaterials as end-products of their bioconversion, whose potential applications in biomedicine, optoelectronics and environmental engineering are still under investigation. Here, the occurrence, the use and the toxicity of Se-and Te-compounds will be briefly overviewed, while the microbial mechanisms of chalcogen-oxyanions bioprocessing, as well as the microbialbased strategies used for bioremediation approaches will be extensively described. Biosorption 132Biosorption 136Microbial-Based Bioremediation of Selenium and Tellurium Compounds

Influence of Bacterial Physiology on Processing of Selenite, Biogenesis of Nanomaterials and Their Thermodynamic Stability

“…The investigation conducted to unveil potential mechanism(s) exploited by MPV1 to cope with increasing concentrations of SeO 3 2− (0.5–10 mM) highlighted the growth and oxyanion removal rates (Figure 1a,b, Table 1) comparable to those described for most SeO 3 2− tolerant bacteria [3,29,30,31,32,33,34,35]. Since Se oxyanions exceeding 2.5 mM reappeared in the growth medium upon exposure to 3, 5, and 10 mM SeO 3 2− (Figure 1b, Table 1), 2.5 mM SeO 3 2− appears to be the threshold concentration biotically processed by MPV1 cells under these experimental conditions, as also observed in the case of Moraxella bovis [36].…”

Fungal transformation of selenium and tellurium located in a volcanogenic sulfide deposit

“…Reduction and methylation in particular have been employed successfully for bioremediation of Se‐contaminated waters and sediments through immobilization and volatilization respectively (e.g. Lawson and Macy, ; Cantafio et al ., ; Brady et al ., ; Soda et al ., ; Mal et al ., ; Piacenza et al ., ,b). In recent years, with growing concern about the security of supply of strategic elements for electronic, digital and environmentally sustainable (bio)technologies, microbial processes are viewed as an important part of the suite of approaches that may be necessary for element biorecovery (Nancharaiah et al ., ; Liang and Gadd, ).…”

Extreme Environments and High-Level Bacterial Tellurite Resistance

“…The neutralization of toxic oxyanions using chemicals and resins has been employed [169,170]; however, they present problems related to their high cost and the inherent fact that they proliferate the release of xenobiotic compounds themselves. More interest in environmentally-friendly, 'greener' methods of dealing with tellurite has arisen, with biological approaches appearing to be the ideal way of cleaning up pollutants [12,171]. Microbes with the ability to reduce oxyanions from highly toxic states to less toxic elemental forms as a means to remediate contaminated sites have been in the spotlight.…”

“…The removal of xenobiotics, metals, and radioactive compounds through bioremediation has been explored [31,[171][172][173][174][175][176][177], but little has been proposed regarding tellurite treatments. The use of microbial communities, i.e., Pseudomonas mendocina, strain MCM B-180 [177], and Pseudoalteromonas sp., EPR3 [40], has been investigated [12,178,179]. The most effective bacterium for tellurite removal is currently P. mendocina, strain MCM B-180, performing optimally at a tellurite concentration of 10 µ g/mL taking 72 h to remove 100 µ g/mL (1.4 mg/L/h) [180].…”

“…This is mainly due to the fact that the latter metals have long been known as essential for life through their involvement in many cellular activities [6][7][8]. Bacterial interactions with tellurite have received attention [9][10][11][12], but much is still unknown about high-level resistance. In recent years, there has been more focus in this area due to increased environmental contamination from industrial activities [13,14].…”