The essential toxin: The changing perception of selenium in environmental sciences
Lenz, M. ; Lens, P.N.L. - \ 2009
Science of the Total Environment 407 (2009)12. - ISSN 0048-9697 - p. 3620 - 3633.
zero-valent iron - enterobacter-cloacae sld1a-1 - agricultural drainage water - selenate-reducing bacterium - permeable reactive barriers - membrane biofilm reactor - elemental red selenium - acid-mine drainage - bacillus sp sf-1 - respiring bacteria
During the last decades, the perception of selenium has undergone substantial changes. While its toxic effects were recognized causing hair and hoof loss in animals during the 1930s, its essential role in microbial, animal and human metabolism has been recognized later, i.e. with the discovery of selenium deficiency causing ¿white muscle disease¿ in feedstock in the 1950s. Nowadays, the positive effect of systematic selenium supplementation is discussed in manifold topics such as cancer or diabetes prevention and avian influenza susceptibility. Treatment of selenium containing waste streams poses a notable challenge to environmental engineers, and to date no ultimate solution has been found for e.g. the selenium contamination in agricultural areas of the western USA. For the future, selenium contamination carries an imminent danger, if the increasing energy demand is covered by fossil fuel combustion, which will lead to major selenium emission and toxicity. This review presents current knowledge of selenium¿s role in environmental sciences and outlines potentially feasible treatment options targeting a variety of selenium contaminated waste streams
Microbiology of synthesis gas fermentation for biofuel production
Henstra, A.M. ; Sipma, J. ; Rinzema, A. ; Stams, A.J.M. - \ 2007
Current Opinion in Biotechnology 18 (2007)3. - ISSN 0958-1669 - p. 200 - 206.
membrane biofilm reactor - carbon-monoxide - sp-nov. - gen. nov. - carboxydothermus-hydrogenoformans - butyribacterium-methylotrophicum - clostridium-thermoaceticum - hydrogenogenic bacterium - rhodospirillum-rubrum - oxidized contaminants
A significant portion of biomass sources like straw and wood is poorly degradable and cannot be converted to biofuels by microorganisms. The gasification of this waste material to produce synthesis gas (or syngas) could offer a solution to this problem, as microorganisms that convert CO and H2 (the essential components of syngas) to multicarbon compounds are available. These are predominantly mesophilic microorganisms that produce short-chain fatty acids and alcohols from CO and H2. Additionally, hydrogen can be produced by carboxydotrophic hydrogenogenic bacteria that convert CO and H2O to H2 and CO2. The production of ethanol through syngas fermentation is already available as a commercial process. The use of thermophilic microorganisms for these processes could offer some advantages; however, to date, few thermophiles are known that grow well on syngas and produce organic compounds. The identification of new isolates that would broaden the product range of syngas fermentations is desirable. Metabolic engineering could be employed to broaden the variety of available products, although genetic tools for such engineering are currently unavailable. Nevertheless, syngas fermenting microorganisms possess advantageous characteristics for biofuel production and hold potential for future engineering efforts.