[Show abstract][Hide abstract] ABSTRACT: The ability of Bacillus sp. 3B6, a bacterial strain isolated from cloud waters, to biotransform saccharides present in the atmosphere was evaluated using in situ 1D and 2D NMR spectroscopy. Bacillus is one of a genus most frequently described in the air and atmospheric waters. Sugars present in these environments have a biogenic origin; they include alditols, monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Bacillus sp. 3B6 was able to efficiently metabolize sugars, which could thus provide sources of energy for this bacterium and allow it to live and to be metabolically active in warm clouds. In addition, a number of these saccharides (L-arabitol, D-fructose, sucrose, D-glucose, cellotetraose, cellulose, and starch) were transformed to EPSs (ExoPolymeric Substances). We have clearly identified the structure of two EPSs as 1,6-α-galactan and partially acetylated polyethylene glycol (AcPEG). 1,6-α-galactan is a newly described polymer. The production of EPSs might protect this bacterium under hostile cloud environment conditions, including low nutrient availability, cold temperature and freeze-thaw processes, UV and radical exposure, and evaporation-condensation processes and thus to desiccation and osmolarity changes. EPSs could also have a potential role in atmospheric processes because they can be considered as secondary organic aerosols and efficient cloud condensation nuclei.
Environmental Science and Technology 11/2014; · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Physico-chemical and biological properties of native polysaccharides could be greatly improved by changing their primary structure, conformation, water solubility or acidity. Chitosan is well-known for its biological properties. Nevertheless, its poor water solubility and its high molecular weight limit its potential uses as biological agent. Enzymatic hydrolysis or regioselective oxidation can be used to overcome these limitations and give birth to new active oligosaccharides.
Firstly, chitosan was C-6 oxidized with NaOCl/NaBr in the presence of TEMPO. 13C NMR, FT-IR and conductimetry analyses confirmed the C-6 oxidation. The production yield was closed to 11 % (w/w) and the molecular weight estimated to 2 kDa by SEC-MALLS experiments. The potential degradability of the derivative was investigated by glycoside hydrolases and polysaccharide lyases. Macerozyme R-10, Glucanex® and a crude extract from Trichoderma reesei IHEM 4122 showed the best degradation results. Finally, the antiparasite activity of the derivative was evaluated against Leishmania infantum LIPA 137. The toxicity of C-6 oxidized chitosan (IC50 = 125µg/mL) was one hundred times higher than current products used against promastigotes.
TEMPO chemistry highlighted the possibility to produce short size, soluble and non-sulfated hyaluronan-like mimetics. These derivatives will be of great interest to design new drugs in leishmaniosis treatment.
3rd EPNOE International Polysaccharide Conference, Nice, France; 10/2013
[Show abstract][Hide abstract] ABSTRACT: Currently, cloud chemistry models are including more detailed and explicit multiphase mechanisms based on laboratory experiments that determine such values as kinetic constants, stability constants of complexes and hydration constants. However, these models are still subject to many uncertainties related to the aqueous chemical mechanism they used. Particularly, the role of oxidants such as iron and hydrogen peroxide in the oxidative capacity of the cloud aqueous phase has typically never been validated against laboratory experimental data. To fill this gap, we adapted the M2C2 model (Model of Multiphase Cloud Chemistry) to simulate irradiation experiments on synthetic aqueous solutions under controlled conditions (e.g., pH, temperature, light intensity) and for actual cloud water samples. Various chemical compounds that purportedly contribute to the oxidative budget in cloud water (i.e., iron, oxidants, such as hydrogen peroxide: H2O2) were considered. Organic compounds (oxalic, formic and acetic acids) were taken into account as target species because they have the potential to form iron complexes and are good indicators of the oxidative capacity of the cloud aqueous phase via their oxidation in this medium. The range of concentrations for all of the chemical compounds evaluated was representative of in situ measurements. Numerical outputs were compared with experimental data that consisted of a time evolution of the concentrations of the target species.
[Show abstract][Hide abstract] ABSTRACT: C-6 oxidized chitosan was produced from chitosan by performing selective oxidation with NaOCl and NaBr using 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) as catalyst. Endocellulase, Celluclast 1.5 L, Glucanex®, Macerozyme R-10, hyaluronidase, hyaluronate lyase, red scorpionfish chitinase, glucuronan lyase and a protein mix from Trichoderma reseei were used to degrade the C-6 oxidized chitosan. Glucanex®, the crude extract from Trichoderma reesei IHEM 4122 and Macerozyme R-10 validated the enzymatic degradation through final hydrolysis yields of the derivative respectively close to 36.4, 20.3 and 12.9% (w/w). The best initial reaction velocity (2.41 U.mL(-1)) was observed for Glucanex®. The antileishmanial activity of the derivative was evaluated against Leishmania infantum LIPA 137. The antibacterial activities against Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 were also tested. Results showed an antileishmanial activity (IC50: 125μg/mL) of the obtained derivatives against Leishmania infantum LIPA 137.
International journal of biological macromolecules 06/2013; · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Some GammaeProteobacteria can catalyze ice formation thereby potentially contributing to the induction of precipitation in supercooled clouds and subsequently to bacterial deposition. Forty-four bacterial strains from cloud water were screened for their capacity to induce freezing. Seven strains (16%) were active at À8 C or warmer and were identified as Pseudomonas syringae, Xanthomonas spp. and Pseudoxanthomonas sp. Phylogenetic analysis revealed that the P. syringae strains in clouds at the Puy de Dôme belonged to clades that are among the most infrequently detected in the environment, while widespread clades were absent suggesting some extent of selection or unusual biogeography of the bacteria at the sampling site. Three strains induced freezing at À3 C while the others nucleated ice at À4 C to À6 C. The freezing profiles revealed that the peaks of activity were centered around À3.5 C, À5 C and/or À8.5 C depending on the strain. The frequency of ice-nuclei (IN) per cell at À6 C was generally below 0.5% and reached up to 4.2% in one strain. We estimated that clouds influenced by vegetated areas would carry between less than 1 and w500 bacterial IN mL À1 of water active between À3 C and À10 C depending on the season. These data will contribute to modeling the impact of bacterial IN on precipitation at regional scales.
[Show abstract][Hide abstract] ABSTRACT: The biodegradability of two polypropylene films with low content of ethylene (a statistical copolymer (PPs) and a block copolymer (PPb) with balanced additions of phenolic antioxidant and pro-oxidants based on Mn, Mn/Fe or Co was studied. Abiotic pre-treatments by accelerated artificial photooxidation and thermooxidation representing about 3–4 years of outdoor weathering, including 3–4 months of exposure to daylight and 3 years in soil were followed by FTIR and SEC measurements. When a controlled oxidation was reached in the films, they were inoculated, in a second step, with the strain Rhodococcus rhodochrous in mineral medium and incubated up to 180 days. The metabolic activity of bacteria was evaluated by measuring ATP content, ADP/ATP ratio and cell viability. Complementary 1H NMR experiments were conducted on the incubation media, with and without cells, in order to monitor the consumption of soluble compounds excreted from the oxidized polymers by R. rhodochrous cells. The main conclusions are that the Co derivatives (with Co content ≥ 150 ppm) must be considered toxic for R. rhodochrous. PP films containing pro-oxidants based on Mn and Mn + Fe give positive results for the biotest (low ADP/ATP ratio, post-development in Petri dishes). However the biodegradability of oxidized PP films is less efficient in comparison to oxidized PE films (see paper published in this journal). This observation may be correlated with the accumulation in the incubation media of oxidized oligomers that cannot be metabolized rapidly by the bacterial cells and/or by the residual crystallinity of PP derivatives.
Polymer Degradation and Stability 04/2013; 98(4):875–884. · 2.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ice nucleation active (INA) biological particles, in particular
microorganisms, were studied in cloud water. Twelve cloud samples were
collected over a period of 16 months from the puy de Dôme summit
(1465 m, France) using sterile cloud droplet impactors. The samples were
characterized through biological (cultures, cell counts) and
physico-chemical measurements (pH, ion concentrations, carbon
content…), and biological ice nuclei were investigated by
droplet-freezing assays from -3°C to -13°C. The concentration of
total INA particles within this temperature range typically varied from
~1 to ~100 per mL of cloud water; the concentrations of biological IN
were several orders of magnitude higher than the values previously
reported for precipitations. At -12°C, at least 76% of the IN were
biological in origin, i.e. they were inactivated by heating at 95°C,
and at temperatures above -8°C only biological material could induce
ice. By culture, 44 Pseudomonas-like strains of bacteria were isolated
from cloud water samples; 16% of them were found INA at the temperature
of -8°C and they were identified as Pseudomonas syringae,
Xanthomonas sp. and Pseudoxanthomonas sp.. Two strains induced freezing
at as warm as -2°C, positioning them among the most active ice
nucleators described so far. We estimated that, in average, 0.18% and
more than 1% of the bacterial cells present in clouds (~104 mL-1) are
INA at the temperatures of -8°C and -12°C, respectively.
References: Attard E. et al. (2012) Effects of atmospheric conditions on
ice nucleation activity of Pseudomonas. Atmospheric Chemistry and
Physics Discussion 12, 9491-9516. Joly M. et al. Ice nucleation activity
of bacteria isolated from cloud water, accepted in Atmospheric
Environment. Vaïtilingom M. et al. (2012) Long-term features of
cloud microbiology at the Puy de Dôme (France). Atmospheric
Environment 56, 88-100.
[Show abstract][Hide abstract] ABSTRACT: Within cloud water, microorganisms are metabolically active and, thus, are expected to contribute to the atmospheric chemistry. This article investigates the interactions between microorganisms and the reactive oxygenated species that are present in cloud water because these chemical compounds drive the oxidant capacity of the cloud system. Real cloud water samples with contrasting features (marine, continental, and urban) were taken from the puy de Dôme mountain (France). The samples exhibited a high microbial biodiversity and complex chemical composition. The media were incubated in the dark and subjected to UV radiation in specifically designed photo-bioreactors. The concentrations of H(2)O(2), organic compounds, and the ATP/ADP ratio were monitored during the incubation period. The microorganisms remained metabolically active in the presence of (•)OH radicals that were photo-produced from H(2)O(2). This oxidant and major carbon compounds (formaldehyde and carboxylic acids) were biodegraded by the endogenous microflora. This work suggests that microorganisms could play a double role in atmospheric chemistry; first, they could directly metabolize organic carbon species, and second, they could reduce the available source of radicals through their oxidative metabolism. Consequently, molecules such as H(2)O(2) would no longer be available for photochemical or other chemical reactions, which would decrease the cloud oxidant capacity.
Proceedings of the National Academy of Sciences 12/2012; · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the first part of the work, we investigated the reactivity toward photogenerated hydroxyl radicals (OH) of seven monocarboxylic acids and six dicarboxylic acids found in natural cloud water. This leads to the proposition of a schematic degradation pathway linking glutaric acid (C5) to complete mineralization into CO2. We report a detailed mechanism on the succinic acid reactivity toward OH leading to the formation of malonic, glyoxylic and consequently oxalic acids and a comparison with reported pathways proposed by the CAPRAM (Chemical Aqueous Phase RAdical Mechanism) is discussed. We also investigated the photooxidation of formic acid under atmospherically relevant conditions leading to the possible formation of oxalic acid via radical mediated recombination.The second part focuses on the polychromatic irradiation (closed to solar irradiation) of a collected cloud aqueous phase showing that irradiation of cloud water leads to the formation of both formic and acetic acids. Carboxylic acid formation increases in the presence of photogenerated hydroxyl radicals from hydrogen peroxide, showing that photooxidation could play a key role in the formation of carboxylic acids under atmospherically relevant conditions.
[Show abstract][Hide abstract] ABSTRACT: Polysaccharides are abundant biopolymers exhibiting various functional activities owing to their structural diversity. These macromolecules, easily renewable, are commonly used in food, oil, cosmetic or pharmaceutical industries. The use of native polysaccharides could be greatly improved by enhancing their properties. In this way, changes in the primary structure of polysaccharides through the addition of anionic/cationic charges, alkyl or sulfated groups modify their conformation, water solubility or acidity. The field of applications of these biopolymers is very wide but closely dependent on their solubility at neutral pH values, on their viscosity in aqueous solutions and on their molecular weight. Chitosan, which is a biopolymer composed of N¬-acetyl-D-glucosamine and D-glucosamine units linked by β-(1-4) bonds, is one example of bioactive polysaccharide insoluble in water at pH 7. Its poor water solubility limits its uses as biological agent. Besides, chitosan is an excellent candidate for chemical modifications, especially to produce glycosaminoglycan mimetics (GAGs), which are known for their dietary or cosmetic properties as the hyaluronic acid. The production of GAGs mimetics from a low cost biopolymer, such as chitosan, highlights major healthy and economic interests.
The first goal of this work was to produce oligoglycosaminoglycans (oligoGAGs) from chitosan by performing its oxidation through the use of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO). Chitosan (90 % deacetylated and with a molecular weight of 150 kDa) was oxidized regiospecifically at C6 with NaOCl and NaBr for approximately 1 h at 4°C in the presence of TEMPO as a catalyst. 13C NMR analyses were carried out and confirmed the regioselective oxidation. Conductivity experiments showed an oxidation degree closed to 94 %. The production yield of these oligoGAGs mimetics was closed to 10.9 % ± 1.4 (w/w) by using this preparation process and their molecular weight closed to 2 KDa. The second aim was to evaluate the potential degradability of these oligoGAGs by glycoside hydrolases (GHs) and polysaccharide lyases (PLs). Cellulase, Celluclast 1.5 L, Glucanex, Macerozyme R-10, glucuronan lyase, rockfish chitinase and enzymatic mix from Trichoderma reseei were used to degrade the oligoGAGs mimetics. Effects of pH and temperature were also studied. Enzymatic degradations were followed by colorimetric assays and the use of Macerozyme R-10 and Glucanex showed the best degradation results.
Finally, TEMPO chemistry showed the possibility to easily produce soluble oligoGAGs mimetics. The short size of the oligoGAGs decreased the amount of enzymes required for the degradation but the biodegradability of these anionic chitosans was validated.
5th European Symposium POLYMERIX 2012, Rennes, France; 06/2012
[Show abstract][Hide abstract] ABSTRACT: Several physico-chemical properties relevant to determine the environmental impact of ionic liquids - aqueous solubility, octanol/water partition coefficient, chromatographically derived lipophilicity and infinite dilution diffusion coefficients in water - were measured in ionic liquids based on pyridinium, ammonium and pyrrolidinium cations with bis(trifluoromethylsulfonyl)imide anions. The influence of the presence of hydroxyl or ester groups in the physico-chemical properties of these liquids was checked. It appeared that the presence of functional oxygenated moieties reduces the lipophilicity of ionic liquids and so decreases the risk of bioaccumulation in environment.
[Show abstract][Hide abstract] ABSTRACT: The physicochemical properties (density, viscosity, and carbon dioxide solubility) of ionic liquids based on pyridinium, pyrrolidinium, and ammonium cations were studied at atmospheric pressure and as a function of temperature between (293 and 343) K. The influence of the inclusion of oxygen functional groups (hydroxyl and ester) in the cations was assessed by comparing their behavior with that of similar nonfunctionalized ionic liquids. We observed that the presence of oxygen groups does not affect the density significantly. The inclusion of an ester group in the alkyl-side chain of pyridinium or ammonium cations greatly increases the viscosity of bis(trifluoromethylsulfonyl)imide ionic liquids (5 times for pyridinium, 2 times for ammonium-based ionic liquids at 293 K), while the presence of hydroxyl groups only slightly increases their viscosity (16 % increase for ammonium at 293 K). Carbon dioxide solubilities are not significantly influenced by the introduction of oxygen functional groups in the cations for the ammonium-based ionic liquids. In the case of the pyridinium-based ionic liquids, the solubility of carbon dioxide significantly decreases (up to a 48 % decrease in mole fraction) due to a defavorable entropic contribution to the Gibbs energy of solvation.
Journal of Chemical & Engineering Data 10/2011; 56(11). · 2.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Several physico-chemical properties relevant to determine the environmental impact of ionic liquids - aqueous solubility, octanol-water partition coefficient and diffusion coefficients in water at infinite dilution - together with toxicity and biodegradability of ionic liquids based on 1-alkyl-3-methylimidazolium cations with or without different oxygenated functional groups (hydroxyl, ester and ether) are studied in this work. The presence of oxygen groups on the imidazolium cation reduces the toxicity of ionic liquids 1-alkyl-3-methylimidazolium with bis(trifluoromethylsulfonyl)imide or octylsulfate anions and simultaneously decreases the value of their octanol-water partition coefficient. The presence of ester functions renders the ionic liquids more easily biodegradable, especially for long alkyl side-chains in the cation but leads to hydrolysis with the formation of reaction products that accumulate. The imidazolium ring is resistant to biodegradability and to abiotic degradation. The oxygen functionalised ionic liquids are more soluble in water and, diffuse more slowly in this medium.
Journal of hazardous materials 10/2011; 198:165-74. · 4.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The kinetics of biodegradation of methanol and formaldehyde in phosphate buffer at pH 7 by 4 bacterial
strains (Pseudomonas spp., Bacillus sp. and Frigoribacterium sp.) isolated from cloud water at the puy de
Dôme mountain have been investigated using 1H and 13C NMR spectroscopy. We showed that biodegradation
occurred at 5 �C and 17�C, respectively average and summertime temperature considered
within the cloud system at this site. They ranged from 10�19 to 10�21 mol cell�1 s�1 both at 5 and 17 �C
for formaldehyde, and from 10 �21 to 10 �23 mol cell�1 s�1 at 5 and 17 �C for methanol. Metabolic intermediates
were identified, with notably production of C3 compounds (glycerol, 1,2- and 1,3-propanediol)
from formaldehyde by the strain Bacillus sp. In order to evaluate to which extent microbiological
oxidation of organic compounds has to be considered as an alternative route to radical chemistry in cloud
water, the biodegradation rates measured were compared with rates related to the reactivity of organic
species with free radicals �OH (daytime chemistry) and NO3 � (nighttime chemistry) under two cloud
situations (urban and remote cases). Clearly, measured biological and chemical reaction rates were in the
same range of magnitude and their relative contribution varies according to the scenarios we tested,
including the temperature of the clouds (5 or 17 �C), the category of the clouds (urban and remote) and
the diurnal cycle (day and nighttime). Except for the degradation of methanol at 5 �C in remote clouds,
our results show that biotransformation processes could be the main sink for C1 compounds in liquid
clouds (T � 5 �Ch“warm cloud”) during the night and both in polluted and non polluted clouds.
[Show abstract][Hide abstract] ABSTRACT: The photochemical behaviour of H2O2 in cloud aqueous phase was investigated from a large amount of in situ cloud droplet sampling data. Then we performed laboratory irradiation experiments of real cloud samples, free from gaseous chemistry, in order to factorise between gas phase and liquid phase photochemical reactions. H2O2 was revealed to be sensitive to solar radiation, with higher concentrations during the day. H2O2 was dependent on the degree of air mass pollution with anthropogenic influences leading to lower values of aqueous H2O2.We observed higher differences between day and night of H2O2 concentrations for air masses influenced by anthropogenic activities (mainly Northern direction) compared to those form remote areas (oceanic). Contrary to this field diurnal trend, during laboratory irradiation experiments of the cloud aqueous phase, the concentration showed a regular linear decrease leading to the conclusion that photolysis is more important than photoproduction in cloud aqueous phase. So the diurnal cycle observed during field measurements is due to the high mass transfer from gas phase to liquid phase favoured by the high dispersion of liquid phase and the high solubility of hydrogen peroxide. As a consequence, H2O2 can act as a photochemical source of OH radicals in cloud aqueous phase.
Atmospheric Research 07/2011; 101(1–2):256-263. · 2.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Catabolism of L-ascorbate by enteric bacteria is well documented, but no study has formally proved that bacteria of the Lactobacillus genus ferment this compound. However, some genes analogous to those of yiaK-S operon and ula regulon, which encoded proteins leading to L-ascorbate degradation by Escherichia coli and Klebsiella pneumoniae , have been identified in the recently sequenced Lactobacillus rhamnosus GG genome. Investigations by HPLC and in vivo (13)C NMR using L-[1,6-(13)C]-ascorbate showed that L. rhamnosus GG, a common probiotic strain, has the ability to catabolize L-ascorbate under anaerobiosis. The main products of the ascorbate degradation have been identified as CO(2), acetate, and lactate. These results are in accordance with the metabolic pathway proposed for the fermentation of L-ascorbate by E. coli.
Journal of Agricultural and Food Chemistry 03/2011; 59(8):4140-7. · 3.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Candida albicans blastospores harvested from 8- (exponential phase) or 48-h (stationary phase) cultures were incubated with 60 × 10−3 M [1-13C]glucose with or without 10−4 M amphotericin B (AmB). The utilization of [1-13C]glucose was monitored by in vivo 13C NMR under anaerobiosis. With exponential phase cells, in the presence of AmB, the consumption of glucose and the production of ethanol, trehalose, and glycerol continuously decreased with time, and after 25 min, the metabolism was blocked. On stationary phase cells AmB had almost no effect on glucose metabolism. Comparison with previous experiments evidenced that AmB induced first K+ leakage, then acidification, and finally a stop of the metabolism. In parallel, in vitro 13C NMR spectra were performed on supernatants and cell-free extracts of yeast suspension incubated under the same conditions. For both exponential and stationary phase cells, AmB induced an increase in the membrane permeability to glycerol; no change was observed for the other metabolites.Key words: Candida albicans, 13C NMR, amphotericin B, glucose metabolism, glycerol.
Canadian Journal of Microbiology 02/2011; 42(7):705-710. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bacillus sp. 3B6, bacterium isolated from cloud water, incubated on sucrose for exopolysaccharide production afforded a complex mixture of levan exopolysaccharide (EPS), fructooligosaccharides (FOSs) of levan and inulin types with different degree of polymerization (dp) and monosaccharides fructose and glucose. By separation of this mixture on size exclusion chromatography eight fractions were obtained. EPS and monosaccharide fractions were the most
abundant. EPS fraction was identified as levan (2,6-βFruf) with two components differing in molecular mass (~ 3500 and ~ 100kDa). Disaccharide fraction contained difructose anhydride DFA IV. 1-Kestose, 6-kestose and neokestose were identified as trisaccharides. Fractions with dp 4 and 5 were mixtures of FOSs of levan (2,6-βFruf) and inulin (1,2-βFruf) type. In one higher molecular mass fraction dominant signals due to DFA IV were present besides those due to short chains of 2,6-βFruf and/or 1,2-βFruf oligomer suggesting the presence of FOSs terminating with DFA IV. The impact of obtained results is i/ in biotechnological applications; ii/ protection of bacteria in extreme conditions of clouds
(temperature, pH); iii/ great importance concerning the cloud condensation nuclei (CCN) properties of strains in the atmosphere.
Carbohydrate Research 01/2011; 346:501-507. · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The photochemical behaviour of H 2 O 2 in cloud aqueous phase was investigated from a large amount of in situ cloud droplet sampling data. Then we performed laboratory irradiation experiments of real cloud samples, free from gaseous chemistry, in order to factorise between gas phase and liquid phase photochemical reactions. H 2 O 2 was revealed to be sensitive to solar radiation, with higher concentrations during the day. H 2 O 2 was dependent on the degree of air mass pollution with anthropogenic influences leading to lower values of aqueous H 2 O 2 . We observed higher differences between day and night of H 2 O 2 concentrations for air masses influenced by anthropogenic activities (mainly Northern direction) compared to those form remote areas (oceanic). Contrary to this field diurnal trend, during laboratory irradiation experiments of the cloud aqueous phase, the concentration showed a regular linear decrease leading to the conclusion that photolysis is more important than photoproduction in cloud aqueous phase. So the diurnal cycle observed during field measurements is due to the high mass transfer from gas phase to liquid phase favoured by the high dispersion of liquid phase and the high solubility of hydrogen peroxide. As a consequence, H 2 O 2 can act as a photochemical source of • OH radicals in cloud aqueous phase.
Atmospheric Research 01/2011; · 2.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bacillus sp. 3B6, bacterium isolated from cloud water, was incubated on sucrose for exopolysaccharide production. Dialysis of the obtained mixture (MWCO 500) afforded dialyzate (DIM) and retentate (RIM). Both were separated by size exclusion chromatography. RIM afforded eight fractions: levan exopolysaccharide (EPS), fructooligosaccharides (FOSs) of levan and inulin types with different degrees of polymerization (dp 2-7) and monosaccharides fructose:glucose=9:1. Levan was composed of two components with molecular mass ~3500 and ~100kDa in the ratio 2.3:1. Disaccharide fraction contained difructose anhydride DFA IV. 1-Kestose, 6-kestose, and neokestose were identified as trisaccharides in the ratio 2:1:3. Fractions with dp 4-7 were mixtures of FOSs of levan (2,6-βFruf) and inulin (1,2-βFruf) type. DIM separation afforded two dominant fractions: monosaccharides with fructose: glucose ratio 1:3; disaccharide fraction contained sucrose only. DIM trisaccharide fraction contained 1-kestose, 6-kestose, and neokestose in the ratio1.5:1:2, penta and hexasaccharide fractions contained FOSs of levan type (2,6-βFruf) containing α-glucose. In the pentasaccharide fraction also the presence of a homopentasaccharide composed of 2,6-linked βFruf units only was identified. Nystose, inulin (1,2-βFruf) type, was identified as DIM tetrasaccharide. Identification of levan 2,6-βFruf and inulin 1,2-βFruf type oligosaccharides in the incubation medium suggests both levansucrase and inulosucrase enzymes activity in Bacillus sp. 3B6.
Carbohydrate research 12/2010; 346(4):501-7. · 2.03 Impact Factor