1,721,076 research outputs found
Ferric citrate fermentation by a Klebsiella oxytoca strain isolated from pyrite mine drainage producing a relevant exopolysaccharide and its potential applications
No full textA Klebsiella oxytoca strain BAS-10 was isolated from pyrite mine drainages. This enterobacter ferments Fe(III)-citrate and Na(I)-citrate. Physiological studies on a relative species K. pneumoniae and Salmonella typhimurium growing on Na(I)-citrate by fermentative metabolism have been already reported. These strains grow on citrate by Na(I)-dependent pathway, forming acetic acid and CO2 as final metabolites. Moreover strain BAS-10 differs from other Klebsiella sp. and other citrate fermenting bacteria that it thrives on high concentrations of Fe(III)-citrate and produces at the stationary phase a thick iron gel. This characteristic is due to the fact that strain BAS-10 synthesizes a branched acid exopolysaccharides (ESP) constituted by the following heptasaccharide: 2)-α-Rha-(13)-β-Gal-(12)-α-Rha-(14)-β-GlcA-[β-GlcA-(14)]-(13)-α-Rha-(13)-α-Rha-(1(2). Recently a regulatory network was disclosed by proteomic analyses of iron-dependent cell processes of Fe(III)-citrate fermentation (3). This wild strain, adapted to mine drainages, copes with iron and other heavy metal toxicity by complexing them outside with EPS. Different metal-EPS had been prepared for nutraceutical, catalysis reactions and antibiotic properties depending on the metal linked to the EPS
Microbial transformation of metals in relation to the biogeochemical cycle
No full textMicrobial transformations and interactions with metals are reviewed in relation to the biogeochemical cycle. Different strategies have been developed by microorganisms to cope with essential and toxic metals. The molecular mechanisms of metal resistance and metal transport are well known from the results of recombinant DNA analysis, sequencing and identification of the protein components involved in regulatory and membrane functions. Other mechanisms of metal interactions have only been studied at physiological level. The bioaccumulation of metals is discussed especially biological mineralization, in which bacteria are the nucleation sites for authigenic mineral formation in the environment. The environmental importance of the opposite process, namely mineral ore oxidation due to the biological leaching of metals from the ore reserve pool is also discussed. -Autho
Microbial transformation of mercury species and their importance in the biogeochemical cycle of mercury
No full textAlkylation of ionic mercury to methylmercury and dimethylmercury by methylcobalamine: simultaneous determination by purge and trap gas chromatography in line with Fourier transform infrared spectroscopy
No full textChromate tolerance in strains of Rhodosporidium toruloides modulated by thiosulphate and sulphur amino acids
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SEAWEED PROTEIN PRODUCTION IN THE VENICE LAGOON: SEASONAL VARIATIONS IN ULVA RIGIDA AND THREE GRACILARIACEAE
No full textFour seaweeds (Ulva rigida, Gracilaria gracilis, Gracilariopsis longissima and
Gracilaria vermiculophylla) were monitored monthly from January to December in the Venice Lagoon. The protein percentages and areal production were measured. The protein content reached 25% in the red seaweeds in winter with averagely low summer values. Protein production peaked in Spring in G. longissima and G. vermiculophylla
Carbohydrate and agar yield: preliminary insights on seasonal variations in Ulva and three Gracilariaceae
No full textFour seaweeds (Ulva rigida, Gracilaria gracilis, Gracilariopsis longissima and
Gracilaria vermiculophylla) were monitored monthly from January to December 2014 in two eutrophic
areas of the Venice Lagoon. The biochemical variations of total carbohydrates and native agar were
measured. The agar yield of G. longissima was the highest, reaching 13.2 tonnes per hectare dwt with
the highest agar percentages exceeding 70% in January
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