Chitosan, xanthan and locust bean gum matrices crosslinked with β-cyclodextrin as green sorbents of aromatic compounds

Three different polysaccharides, xanthan gum, chitosan and locust bean gum, were crosslinked with or without β-cyclodextrin, using citric acid in different ratios, to create ‘green’ hydrogel matrices. The crosslinking of these polysaccharides was produced through an inexpensive and innocuous solvent-free synthesis process. A favorable swelling behavior of the hydrophilic matrices facilitates the sorption of the solutes tested. Interestingly, the amount of β-cyclodextrin groups is not the only factor to yield the best sorption capability for hydrophobic model molecules: polysaccharides themselves also influence the sorption depending on their characteristic functional groups, the conformation of their chains and, as mentioned above, their degrees of swelling. In order to ascertain the effect of the polysaccharides on the sorption capabilities of a model sorbate (1-naphthol), isotherms using a wide range of solute concentrations were analyzed, and the Hill equation yielded the best fitting results and provided some insight into the mechanisms of interaction

Locust bean gum, a vegetable hydrocolloid with industrial and biopharmaceutical applications

Locust bean gum (LBG), a vegetable galactomannan extracted from carob tree seeds, is extensively used in the food industry as a thickening agent (E410). Its molecular conformation in aqueous solutions determines its solubility and rheological performance. LBG is an interesting polysaccharide also because of its synergistic behavior with other biopolymers (xanthan gum, carrageenan, etc.). In addition, this hydrocolloid is easily modified by derivatization or crosslinking. These LBG-related products, besides their applications in the food industry, can be used as encapsulation and drug delivery devices, packaging materials, batteries, and catalyst supports, among other biopharmaceutical and industrial uses. As the new derivatized or crosslinked polymers based on LBG are mainly biodegradable and non-toxic, the use of this polysaccharide (by itself or combined with other biopolymers) will contribute to generating greener products, considering the origin of raw materials used, the modification procedures selected and the final destination of the products

Solventless crosslinking of chitosan, xanthan, and locust bean gum networks functionalized with beta-Cyclodextrin

The incorporation of cyclodextrins into polymeric crosslinked gels of hydrophilic nature can be useful for promoting the sorption of hydrophobic molecules and/or modulating the release of active principles. The covalent addition of these excipients to the matrix integrates their solubilizing effect that can contribute to increase the capacity of retention of hydrophobic substances. In this study, three diverse polysaccharides, chitosan, xanthan gum, and locust bean gum, were crosslinked with or withoutβ-cyclodextrin, using citric acid in different ratios, to create hydrogel matrices. Through a green synthetic path, the efficient production of soluble and insoluble (hydrogel) networks functionalized with β-cyclodextrin was achieved by means of a solventless procedure. The characterization of their chemical composition, swelling in water, and their sorption and release behavior were also carried out in this work

C, N, O Abundances in the Most Metal-Poor Damped Lyman alpha Systems

This study focuses on some of the most metal-poor damped Lyman alpha absorbers known in the spectra of high redshift QSOs, using new and archival observations obtained with UV-sensitive echelle spectrographs on the Keck and VLT telescopes. The weakness and simple velocity structure of the absorption lines in these systems allows us to measure the abundances of several elements, and in particular those of C, N, and O, a group that is difficult to study in DLAs of more typical metallicities. We find that when the oxygen abundance is less than about 1/100 of solar, the C/O ratio in high redshift DLAs and sub-DLAs matches that of halo stars of similar metallicity and shows higher values than expected from galactic chemical evolution models based on conventional stellar yields. Furthermore, there are indications that at these low metallicities the N/O ratio may also be above simple expectations and may exhibit a minimum value, as proposed by Centurion and her collaborators in 2003. Both results can be interpreted as evidence for enhanced production of C and N by massive stars in the first few episodes of star formation, in our Galaxy and in the distant proto-galaxies seen as QSO absorbers. The higher stellar yields implied may have an origin in stellar rotation which promotes mixing in the stars' interiors, as considered in some recent model calculations. We briefly discuss the relevance of these results to current ideas on the origin of metals in the intergalactic medium and the universality of the stellar initial mass function.Comment: 17 pages, 9 Figures, Accepted for publication in Monthly Notices of the Royal Astronomical Societ

The Enrichment History of the Intergalactic Medium: Measuring the CIV/HI Ratio in the Lyman Alpha Forest

We have obtained an exceptionally high S/N, high resolution spectrum of the gravitationally lensed quasar Q1422+231 in order to investigate the metal enrichment of the IGM. A column density distribution function (CDDF) is determined for CIV, which is well fit by a power law with index 1.44 +/- 0.05. Once a correction for incompleteness is applied, we find that the CDDF is consistent with a power law down to log N(CIV) = 11.75, a factor of 10 more sensitive than previously determined. In order to determine whether the CIV enrichment extends to even lower column density HI clouds, we find that an analysis of individual pixel optical depths is more robust than the stacking technique. The results obtained from this optical depth method are compared with analyses of simulated spectra enriched with varying CIV enrichment recipes. From these simulations, we conclude that more CIV than is currently directly detected in Q1422+231 is required to reproduce the optical depths determined from the data, consistent with the conclusions drawn from consideration of the power law distribution. (Abridged)Comment: Accepted for publication by AJ. 10 pages of text plus 11 figures and 2 table

Chitosan, xanthan and locust bean gum matrices crosslinked with β-cyclodextrin as green sorbents of aromatic compounds

Three different polysaccharides, xanthan gum, chitosan and locust bean gum, were crosslinked with or without β-cyclodextrin, using citric acid in different ratios, to create ‘green’ hydrogel matrices. The crosslinking of these polysaccharides was produced through an inexpensive and innocuous solvent-free synthesis process. A favorable swelling behavior of the hydrophilic matrices facilitates the sorption of the solutes tested. Interestingly, the amount of β-cyclodextrin groups is not the only factor to yield the best sorption capability for hydrophobic model molecules: polysaccharides themselves also influence the sorption depending on their characteristic functional groups, the conformation of their chains and, as mentioned above, their degrees of swelling. In order to ascertain the effect of the polysaccharides on the sorption capabilities of a model sorbate (1-naphthol), isotherms using a wide range of solute concentrations were analyzed, and the Hill equation yielded the best fitting results and provided some insight into the mechanisms of interaction

Locust bean gum, a vegetable hydrocolloid with industrial and biopharmaceutical applications

Locust bean gum (LBG), a vegetable galactomannan extracted from carob tree seeds, is extensively used in the food industry as a thickening agent (E410). Its molecular conformation in aqueous solutions determines its solubility and rheological performance. LBG is an interesting polysaccharide also because of its synergistic behavior with other biopolymers (xanthan gum, carrageenan, etc.). In addition, this hydrocolloid is easily modified by derivatization or crosslinking. These LBG-related products, besides their applications in the food industry, can be used as encapsulation and drug delivery devices, packaging materials, batteries, and catalyst supports, among other biopharmaceutical and industrial uses. As the new derivatized or crosslinked polymers based on LBG are mainly biodegradable and non-toxic, the use of this polysaccharide (by itself or combined with other biopolymers) will contribute to generating greener products, considering the origin of raw materials used, the modification procedures selected and the final destination of the products

Preparation of beta-cyclodextrin/polysaccharide foams using saponin

Cyclodextrins, cyclic oligosaccharides with a hydrophobic cavity that form inclusion complexes with nonpolar molecules, can be used to functionalize other polysaccharides. Xanthan gum, locust bean gum or chitosan can be crosslinked using citric acid in the presence of ß-cyclodextrin to produce insoluble matrices. In this work, polymeric foams based on those polysaccharides and saponin have been prepared using a green synthesis method to increase the porosity of the matrices. The saponin of soapbark (Quillaja saponaria) has been used to obtain foams using different procedures. The influence of the synthesis path on the porosity of the materials and their corresponding sorption capacities in the aqueous phase were evaluated

Preparation of beta-cyclodextrin/polysaccharide foams using saponin

Cyclodextrins, cyclic oligosaccharides with a hydrophobic cavity that form inclusion complexes with nonpolar molecules, can be used to functionalize other polysaccharides. Xanthan gum, locust bean gum or chitosan can be crosslinked using citric acid in the presence of ß-cyclodextrin to produce insoluble matrices. In this work, polymeric foams based on those polysaccharides and saponin have been prepared using a green synthesis method to increase the porosity of the matrices. The saponin of soapbark (Quillaja saponaria) has been used to obtain foams using different procedures. The influence of the synthesis path on the porosity of the materials and their corresponding sorption capacities in the aqueous phase were evaluated

Green synthesis and chemometric characterization of hydrophobic xanthan matrices: interactions with phenolic compounds

Polysaccharides such as xanthan, locust bean gum or chitosan are easily crosslinked and purified using citric acid in an ecofriendly process. In order to achieve an improved sorption capability towards hydrophobic solutes, β-cyclodextrin, a cyclic oligosaccharide, and lignin, a natural aromatic polymer, are incorporated in the same process. Once crosslinked, the influence of these on the sorption capacities towards model solutes has been assessed by comparing the sorption isotherms of matrices with or without the hydrophobic modifications. The sorption capacities of these materials for different phenolic compounds have also been tested to ascertain their efficiencies as a function of their affinities to β-cyclodextrin cavities and/or their partition coefficients. In addition, these functionalized carbohydrate matrices were successfully characterized by principal component analysis, which is a useful tool to select the most appropriate polymers to interact with a specific molecul