Bio-generated metal binding polysaccharides as catalysts for synthetic applications and organic pollutant transformations

Aqueous biphasic treatment of some nitrocompounds with hydrogen in the presence of a biogenerated Pd-polysaccharide

“…This species, containing 1.7% of palladium (wt%), presented particles with diameters ranging from about 30 nm for the smallest ones up to 550 nm in the case of particles aggregation; moreover, XPS measurements showed that palladium was initially present as Pd(II) ions and during hydrogenation a part of it was transformed in Pd(0) [16]. Pd-EPS was successfully employed as catalyst precursor in the aqueous biphasic hydrodechlorination of aromatic chlorocompounds and in the hydrogenation of carbon-carbon double bonds [15,16]. On the basis of these results, we decided to explore the activity and selectivity of this species also in the reduction of some model nitro compounds, being the corresponding amino-compounds widespread used in the chemical industry for the production of pigments, azo dyes, rubbers, amino-resins, herbicides and other fine chemicals [17,18].…”

“…In particular, a strain of Klebsiella oxytoca BAS-10, isolated from acid mine drainage of pyrite mines, was found to be able to produce a peculiar exopolysaccharide (EPS), during citrate fermentation, that is able to carry out or bind different metallic salts or metals as such [13,14]. So the BAS-10 strain, grown aerobically in static mode in the presence of sodium citrate as sole carbon and energy source and of Pd(NO 3 ) 2 added to the culture, may produce palladium species bound to the exopolysaccharide EPS; after centrifugation to eliminate bacterial cells, the colloidal material is dried out under vacuum to obtain Pd-EPS as a solid material to be already used in some Pd-catalyzed processes [15,16]. In this paper we decided to study further applications of this catalyst on substrates containing nitro groups to reduce.…”

Iron-Reducing Bacteria and Iron Nanostructures

“…The media was supplemented with 50 mM of ferric citrate which provides ferric ions as electron acceptor and also citrate as organic substrate for fermentation [10,19]. The bacteria consume citrate as energy and carbon sources in anaerobic culture condition [8][9][10]. The cultivation is usually performed in the dark or under dim light at room temperature and under protected atmosphere against oxygen.…”

“…Klebsiella oxytoca is one of these bacteria which produce a secretory exopolysaccharide. The polysaccharide is attached to the bacterial cell surface and composed of galactose, glucuronic acid, and rhamnose that display metal-binding properties [9,47]. As mentioned above, in anaerobic environments, Klebsiella oxytoca ferments citrate to CO 2 and acetic acid joined with reduction of ferric ions to ferrous.…”

“…From gram staining point of view IRB are not restricted in one category and both gram-positive and gram-negative bacteria can be found among them [5][6][7][8][9][10]. This group of bacteria is now so divergent and belong to gamma and delta Proteobacteria including verity of genus and species such as Stenotrophomonas maltophilia, Brachymonas denitrificans, Paracolobacterum aerogenoides, Serratia marcescens, Aerobacter aerogenes, Citrobacter freundii, Bacillus circuhzns, Bacillus polymyxa, Bacillus alvei, Bacillus cereus, Bacillus pumilus, Bacillus subtilis, Bacillus cereus, Bacillus sphaericus, Pseudomonas aeruginosa, Pseudomonas denitrificans, Pseudomonas stutzeri, Pseudomonas fluorescens, and Pseudomonas putida [11][12][13].…”