The gut microbiota (GM) is the whole of commensal, symbiotic, and pathogenic microorganisms living in our intestine. The GM–host interactions contribute to the maturation of the host immune system, ...modulating its systemic response. It is well documented that GM can interact with non-enteral cells such as immune cells, dendritic cells, and hepatocytes, producing molecules such as short-chain fatty acids, indole derivatives, polyamines, and secondary bile acid. The receptors for some of these molecules are expressed on immune cells, and modulate the differentiation of T effector and regulatory cells: this is the reason why dysbiosis is correlated with several autoimmune, metabolic, and neurodegenerative diseases. Due to the close interplay between immune and bone cells, GM has a central role in maintaining bone health and influences bone turnover and density. GM can improve bone health also increasing calcium absorption and modulating the production of gut serotonin, a molecule that interacts with bone cells and has been suggested to act as a bone mass regulator. Thus, GM manipulation by consumption of antibiotics, changes in dietary habits, and the use of pre- and probiotics may affect bone health. This review summarizes evidences on the influence of GM on immune system and on bone turnover and density and how GM manipulation may influence bone health.
Ulvan, the sulfated cell-wall polysaccharides from green seaweeds (
Ulva species), presents structural and functional properties of interest for different applications. Its extraction yield in water ...varies depending on the species, the period of collect and the mode of conservation of algae. To identify limits of extraction, the structure and interactions of ulvan in the cell wall of
Ulva were investigated following a sequential solvent extraction. Hot sodium oxalate and hot dilute HCl were the two major extracts. Other solvents affecting protein structure or low hydrogen bonded polymers yielded minor ulvan fractions but affected solid state
13C NMR spectra indicating that proteins likely contributed to cross-link and/or to entrap
Ulva cell wall polysaccharides. Ulvan-lyase degradation showed that ulvan consisted in a wide continuum of related polysaccharides differing in the extent and type of fine structural characteristics. Besides solvent acidity, particle size of seaweeds was an important parameter controlling the ulvan extraction efficiency. Major ulvan cell wall interactions were discussed with regard to ionic interactions, covalent linkages and peculiar solution behavior of ulvan in various physicochemical environments.
The impact of freezing, freeze-drying, hot-air drying, brining and dry salting stabilization methods of
Ulva
rotundata has been studied on the yield, physico-chemical characteristics and rheological ...properties of ulvan. Frozen (−30 and −80
°C) and freeze-dried algae yielded ulvan extracts mainly composed of high molecular weight polysaccharides. These had the highest intrinsic viscosity and conservation modulus (
G′) as copper/borate gels compared to ulvan from fresh algae (taken as a reference) or ulvan extracted from algae stabilized by other means. Cold stabilizations of algae yielded the lowest amounts of ulvan. High ulvan yields were obtained from
Ulva air-dried at 50 and 70
°C but that at 50
°C was lower than that at 70
°C. Gelling properties and intrinsic viscosities from these ulvans were better than that of fresh algae but lower than from cold treated seaweeds. Brining induced ulvan degradation with poor rheological properties of the extracts compared to ulvan from fresh algae. However, this process appears to ease extraction of polysaccharides. Compared to fresh algae, salted seaweeds stored at room temperature yielded degraded ulvan. Decreasing the salting process temperature to 4
°C preserved ulvan composition, structure and properties. However,
Ulva salting hinders drastically ulvan extraction. The different stabilization processes affected the chemical composition of ulvan extracts and in particular, sulphate and protein contents. The results show that different stabilization conditions of
Ulva biomass can be selected according to their cost-effectiveness and the required ulvan chemical and macromolecular characteristics.
► Green seaweed stranded on beaches as agricultural anaerobic digestion co-substrate. ► Methanogenic potential of green seaweed is low. ► Biogas produced by co-digestion with animal slurry contained ...high level of H2S. ► Further control of H2S production by selective biomass inhibitor is not efficient enough.
Seaweed (Ulva sp.) stranded on beaches were utilized as co-substrate for anaerobic digestion of pig slurry in three-month co-digestion tests in pilot scale anaerobic digesters in the laboratory. The methanogenic potential of Ulva sp. was low compared to that of other potential co-substrates available for use by farmers: 148Nm3CH4/t of volatile solids or 19Nm3CH4/t of crude product. When used as a co-substrate with pig manure (48%/52% w/w), Ulva sp. seaweed did not notably disrupt the process of digestion; however, after pilot stabilisation, biogas produced contained 3.5% H2S, making it unsuitable for energy recovery without treatment. Sequentially addition of the sulphate reduction inhibitor, potassium molybdate, to a final concentration of 3mM, temporarily reduced H2S emissions, but was unable to sustain this reduction over the three-month period. According to these pilot tests, the use of seaweed stranded on beaches as co-substrate in farm-based biogas plants shows some limitations.
We have used the Whole Atmosphere Community Climate Model to produce a small (three‐member) ensemble of simulations of the period 1950–2003. Comparison of model results against available observations ...shows that for the most part, the model is able to reproduce well the observed trends in zonal mean temperature and ozone, both as regards their magnitude and their distribution in latitude and altitude. Calculated trends in water vapor, on the other hand, are not at all consistent with observations from either the HALOE satellite instrument or the Boulder, Colorado, hygrosonde data set. We show that such lack of agreement is actually to be expected because water vapor has various sources of low‐frequency variability (heating due to volcanic eruptions, the quasi‐biennial oscillation and El Niño–Southern Oscillation) that can confound the determination of secular trends. The simulations also reveal the presence of other interesting behavior, such as the lack of any significant temperature trend near the mesopause, a decrease in the stratospheric age of air, and the rare occurrence of an extremely disturbed Southern Hemisphere winter.
The water-soluble cell wall polysaccharides from green seaweeds of Ulva spp. (Ulvales, Chlorophyta), referred to as ulvan, demonstrate composition- and structure-related functional properties. ...Mid-infrared spectroscopy combined with chemometric techniques was investigated as a means to rapidly predict the chemical composition of ulvan extracts. A calibration was realized with 41 ulvan extracts from two Ulva species. The variables studied included the constituent sugars (rhamnose, xylose, glucose, galactose, glucuronic acid, iduronic acid), protein, and sulfate contents. The correlation between Fourier transform infrared and chemical data was developed using partial least squares (PLS) regression with full cross-validation (leave one out). The coefficients of determination in cross-validation ( graphic removed ) and the standard error in cross-validation were determined for each variable. The PLS model validation resulted in a coefficient of determination ( graphic removed ) and a standard error in prediction. Good predictions were obtained for rhamnose ( graphic removed = 0.9244), xylose ( graphic removed = 0.8758), glucuronic acid ( graphic removed = 0.9415), and sulfate ( graphic removed = 0.9218), which are the main ulvan constituents. However, minor components such as proteins, glucose, galactose, and iduronic acid were not correctly predicted. This study showed that mid-infrared spectroscopy combined with PLS regression is a reliable and fast method for the quantification of the main chemical constituents of ulvan extracts.
Microalgae are autotrophs and CO.sub.2 fixers with great potential to produce biofuels in a sustainable way, however the high cost of biomass production is a challenge. Mixotrophic growth of ...microalgae has been presented as a great alternative to achieve economic sustainability. Thus, the present work reports the energetic characterization of S. platensis biomasses cultivated under autotrophic (A) and mixotrophic conditions using cheese whey waste at different concentrations, 2.5 (M2.5), 5.0 (M5) and 10.0% (M10), in order to analyze the potential production of valuable chemicals and bio-oil by TGA/DTG and Py-GC/MS. The biochemical compositions of the studied biomasses were different due to the influence of different culture mediums. As the whey concentration increased, there was an increase in the carbohydrate content and a decrease in the protein content, which influenced the elemental composition, calorific value, TGA and volatile compounds evaluated by Py-GC/MS at 450°C, 550°C and 650°C. Sample M10 had lower protein content and formed a smaller amount of nitrogenates compounds by pyrolysis at all temperatures evaluated. There was a reduction of 43.8% (450º), 45.6% (550ºC) and 23.8% (650ºC) in the formation of nitrogenates compounds in relation to sample A. Moreover, the temperature also showed a considerable effect in the formation of volatile compounds. The highest yields of nitrogenates compounds, phenols and aromatic and non-aromatic hydrocarbons were observed at 650ºC. The oxygenated, and N and O containing compounds decreased as the temperature increased. Hydrocarbons such as toluene, heptadecane and heneicosane were produced by S.platensis pyrolysis, which makes this biomass attractive for production of high quality bio-oil and valuable chemicals. Therefore, the results showed that it is possible to decrease the formation of nitrogen compounds via manipulation of growth conditions and temperature.
Recent advances in developing accurate, physics‐based models of the coupled ionosphere‐thermosphere (CIT) system have now made these models an integral part of next‐generation space weather ...prediction capabilities. These advances have produced a better understanding of how the CIT is affected by variability in the neutral lower atmosphere. However, the impacts on the CIT of lower atmospheric variability over time scales with characteristic periods longer than ~10 days have received little attention, despite clear evidence of this variability in atmospheric circulation patterns throughout the stratosphere, mesosphere, and lower thermosphere. This review synthesizes the state of knowledge on long‐term variability (>10 days) originating in the lower atmosphere and its impacts on the CIT, highlighting the following critical points and challenges: (a) planetary wave oscillations are likely to couple the lower and upper atmospheres, especially those corresponding to normal modes of the atmosphere, but it remains unclear whether they impact the ionosphere directly via wind‐dynamo coupling, or indirectly via modulation of solar and lunar tides; (b) while fast moving planetary wave oscillations are ubiquitous in the CIT especially during solstices, there is only sporadic evidence that the slowest moving modes are also present in the upper atmosphere; (c) there is abundant evidence of long‐term variations of tidal amplitudes in the CIT, but how and why such variations occur still remain; (d) interseasonal variations associated with major tropospheric and stratospheric variability have been observed, but the physical pathways are still poorly understood.
Key Points
Large‐scale oscillations with periods longer than 10 days are a potential source of space weather predictability
Ionospheric signatures of intraseasonal behavior are ubiquitous, but their origins are poorly understood
Observational and modeling studies of pathways linking oscillations from the lower atmosphere to the ionosphere are needed
To investigate ionosphere variability during the 2009 sudden stratosphere warming (SSW), we present simulation results that combine the Whole Atmosphere Community Climate Model Extended version and ...the thermosphere‐ionosphere‐mesosphere electrodynamics general circulation model (TIME‐GCM). The simulations reveal notable enhancements in both the migrating semidiurnal solar (SW2) and lunar (M2) tides during the SSW. The SW2 and M2 amplitudes reach ∼50 m s−1 and ∼40 m s−1, respectively, in zonal wind at E region altitudes. The dramatic increase in the M2 at these altitudes influences the dynamo generation of electric fields, and the importance of the M2 on the ionosphere variability during the 2009 SSW is demonstrated by comparing simulations with and without the M2. TIME‐GCM simulations that incorporate the M2 are found to be in good agreement with Jicamarca Incoherent Scatter Radar vertical plasma drifts and Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations of the maximum F region electron density. The agreement with observations is worse if the M2 is not included in the simulation, demonstrating that the lunar tide is an important contributor to the ionosphere variability during the 2009 SSW. We additionally investigate sources of the F region electron density variability during the SSW. The primary driver of the electron density variability is changes in electric fields. Changes in meridional neutral winds and thermosphere composition are found to also contribute to the electron density variability during the 2009 SSW. The electron density variability for the 2009 SSW is therefore not solely due to variability in electric fields as previously thought.
Key Points
Lunar tide is important for simulating ionosphere during the 2009 SSW
Electric field changes are primary cause of electron density variability
Meridional winds and thermosphere composition also influence electron density
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