The role of peroxiredoxins PrxA and PrxB in the antioxidant response, carbon utilization and development in Aspergillus nidulans.

In addition to their role in the breakdown of H2O2, some peroxiredoxins (Prxs) have chaperone and H2O2 sensing functions. Acting as an H2O2 sensor, Prx Gpx3 transfers the oxidant signal to the transcription factor Yap1, involved in the antioxidant response in Saccharomyces cerevisiae. We have shown that Aspergillus nidulans Yap1 ortholog NapA is necessary for the antioxidant response, the utilization of arabinose, fructose and ethanol, and for proper development. To address the Prx roles in these processes, we generated and characterized mutants lacking peroxiredoxins PrxA, PrxB, PrxC, or TpxC. Our results show that the elimination of peroxiredoxins PrxC or TpxC does not produce any distinguishable phenotype. In contrast, the elimination of atypical 2-cysteine peroxiredoxins PrxA and PrxB produce different mutant phenotypes. ΔprxA, ΔnapA and ΔprxA ΔnapA mutants are equally sensitive to H2O2 and menadione, while PrxB is dispensable for this. However, the sensitivity of ΔprxA and ΔprxA ΔnapA mutants is increased by the lack of PrxB. Moreover, PrxB is required for arabinose and ethanol utilization and fruiting body cell wall pigmentation. PrxA expression is partially independent of NapA, and the replacement of peroxidatic cysteine 61 by serine (C61S) is enough to cause oxidative stress sensitivity and prevent NapA nuclear accumulation in response to H2O2, indicating its critical role in H2O2 sensing. Our results show that despite their high similarity, PrxA and PrxB play differential roles in Aspergillus nidulans antioxidant response, carbon utilization and development.

Fine structural features and antioxidant capacity of ferulated arabinoxylans extracted from nixtamalized maize bran.

BACKGROUND: The nixtamalization process improves the nutritional and technological properties of maize. This process generates nixtamalized maize bran as a by-product, which is a source of arabinoxylans (AX). AX are polysaccharides constituted of a xylose backbone with mono- or di-arabinose substitutions, which can be ester-linked to ferulic acid (FA). The present study investigated the fine structural features and antioxidant capacity (AC) of nixtamalized maize bran arabinoxylans (MBAX) to comprehend the structure-radical scavenging capacity relationship in this polysaccharide deeply. RESULTS: MBAX presented a molecular weight, intrinsic viscosity, and hydrodynamic radius of 674 kDa, 1.8 dL g-1 , and 24.6 nm, respectively. The arabinose-to-xylose ratio (A/X) and FA content were 0.74 and 0.25 g kg-1 polysaccharide, respectively. MBAX contained dimers (di-FA) and trimer (tri-FA) of FA (0.14 and 0.07 g kg-1 polysaccharide, respectively). The main di-FA isomer was the 8-5' structure (80%). Fourier transform infrared spectroscopy confirmed MBAX molecular identity, and the second derivate of the spectral data revealed a band at 958 cm-1 related to the presence of arabinose disubstitution. 1 H-Nuclear magnetic resonance spectroscopy showed mono- and di-arabinose substitution in the xylan backbone with more monosubstituted residues. MBAX registered an AC of 25 and 20 µmol Trolox equivalents g-1 polysaccharide despite a low FA content, using ABTS (2,2'-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid) and DPPH (1,1-diphenyl-2-picrylhydrazyl) methods, respectively. CONCLUSION: AC in MBAX could be related to the high A/X ratio (mainly monosubstitution) and the high 8-5' di-FA proportion in this polysaccharide. © 2023 Society of Chemical Industry.

Isolation, characterisation and complement fixation activity of acidic polysaccharides from Argemone mexicana used as antimalarials in Mali.

CONTEXT: Global studies on Argemone mexicana L. (Papaveraceae) traditionally used against malaria in Mali are limited to its low-mass compounds activities, and little information on its bioactive polysaccharides is available. OBJECTIVE: This study determines the structure and the immunomodulatory activity of polysaccharides from aerial parts of A. mexicana. MATERIALS AND METHODS: Acidic polysaccharides from this plant material named HMAmA1 and HMAmA2 were isolated from water extracts. Their monosaccharide composition was determined by gas chromatography. Glycosidic linkages were determined using GC-MS. NMR was also applied. The polymers were tested for effects on the human complement system in vitro at different doses. RESULTS: The monosaccharide composition showed that the two polysaccharides contained in different amounts the following monomers: arabinose, rhamnose, galactose, and galacturonic acid. Overall structural analysis showed the presence of a low ratio of 1,2-linked rhamnose compared to 1,4-linked galacturonic acid with arabinogalactans substituted on position 4 of rhamnose. NMR data showed the presence of galacturonans alternated by rhamnogalacturonans bearing arabinose and galactose units. α-Linkages were found for l-arabinose, l-rhamnose and d-galacturonic acid, while ß-linkages were found for d-galactose. The two polysaccharides exhibited strong complement fixation activities, with HMAmA1 being the highest potent fraction. ICH50 value of HMAmA1 was 5 µg/mL, compared to the control BPII being 15.9 µg/mL. DISCUSSION AND CONCLUSIONS: Polysaccharides form A. mexicana presented a complement fixation effect. The complement system is an important part of the immune defense, and compounds acting on the cascade are of interest. Therefore, these polymers may be useful as immunodulatory agents.

The potential of extracellular biopolymer production by Mesorhizobium sp. from monosaccharide constituents of lignocellulosic biomass.

OBJECTIVE: The effects of monosaccharide constituents of lignocellulosic materials on exopolysaccharide (EPS) production by Mesorhizobium sp. Semia 816 were studied. RESULTS: According to the results, by using sugars commonly found in lignocellulosic biomass as carbon sources (glucose, arabinose and xylose), no significant differences were observed in the production of EPS, reaching 3.39 g/L, 3.33 g/L and 3.27 g/L, respectively. Differences were observed in monosaccharide composition, mainly in relation to rhamnose and glucuronic acid contents (1.8 times higher when arabinose was compared with xylose). However, the biopolymers showed no differences in relation to rheological properties, with EPS aqueous-based suspensions (1.0% w/v) presenting pseudoplastic behavior, and a slight difference in degradation temperatures. Using soybean hulls hydrolysate as carbon source, slightly higher values were obtained (3.93 g/L). CONCLUSION: The results indicate the potential of the use of lignocellulosic hydrolysates containing these sugars as a source of carbon in the cultivation of Mesorhizobium sp. Semia 816 for the production of EPS with potential industrial applications.

Deconstruction of banana peel for carbohydrate fractionation.

The deconstruction of banana peel for carbohydrate recovery was performed by sequential treatment (acid, alkaline, and enzymatic). The pretreatment with citric acid promoted the extraction of pectin, resulting in a yield of 8%. In addition, xylose and XOS, 348.5 and 17.3 mg/g xylan, respectively, were also quantified in acidic liquor as a result of partial depolymerization of hemicellulose. The spent solid was pretreated with alkaline solution (NaOH or KOH) for delignification and release of residual carbohydrates from the hemicellulose. The yields of xylose and arabinose (225.2 and 174.0 mg/g hemicellulose) were approximately 40% higher in the pretreatment with KOH, while pretreatment with NaOH promoted higher delignification (67%), XOS yield (32.6 mg/g xylan), and preservation of cellulosic fraction. Finally, the spent alkaline solid, rich in cellulose (76%), was treated enzymatically to release glucose, reaching the final concentration of 28.2 g/L. The mass balance showed that through sequential treatment, 9.9 g of xylose, 0.5 g of XOS, and 8.2 g of glucose were obtained from 100 g of raw banana peels, representing 65.8% and 46.5% conversion of hemicellulose and cellulose, respectively. The study of the fractionation of carbohydrates in banana peel proved to be a useful tool for valorization, mainly of the hemicellulose fraction for the production of XOS and xylose with high value applications in the food industry.

Fermentation profiles of the yeast Brettanomyces bruxellensis in d-xylose and l-arabinose aiming its application as a second-generation ethanol producer.

The yeast Brettanomyces bruxellensis is able to ferment the main sugars used in first-generation ethanol production. However, its employment in this industry is prohibitive because the ethanol productivity reached is significantly lower than the observed for Saccharomyces cerevisiae. On the other hand, a possible application of B. bruxellensis in the second-generation ethanol production has been suggested because this yeast is also able to use d-xylose and l-arabinose, the major pentoses released from lignocellulosic material. Although the latter application seems to be reasonable, it has been poorly explored. Therefore, we aimed to evaluate whether or not different industrial strains of B. bruxellensis are able to ferment d-xylose and l-arabinose, both in aerobiosis and oxygen-limited conditions. Three out of nine tested strains were able to assimilate those sugars. When in aerobiosis, B. bruxellensis cells exclusively used them to support biomass formation, and no ethanol was produced. Moreover, whereas l-arabinose was not consumed under oxygen limitation, d-xylose was only slightly used, which resulted in low ethanol yield and productivity. In conclusion, our results showed that d-xylose and l-arabinose are not efficiently converted to ethanol by B. bruxellensis, most likely due to a redox imbalance in the assimilatory pathways of these sugars. Therefore, despite presenting other industrially relevant traits, the employment of B. bruxellensis in second-generation ethanol production depends on the development of genetic engineering strategies to overcome this metabolic bottleneck.

Biosynthesis of polyhydroxyalkanoates from vegetable oil under the co-expression of fadE and phaJ genes in Cupriavidus necator.

The acyl-CoA dehydrogenase (FadE) and (R)-specific enoyl-CoA hydratase (PhaJ) are functionally related to the degradation of fatty acids and the synthesis of polyhydroxyalkanoates (PHAs). To verify this, a recombinant Cupriavidus necator H16 harboring the plasmid -pMPJAS03- with fadE from Escherichia coli strain K12 and phaJ1 from Pseudomonas putida strain KT2440 under the arabinose promoter (araC-PBAD) was constructed. The impact of co-expressing fadE and phaJ genes on C. necator H16/pMPJAS03 maintaining the wild-type synthase on short-chain-length/medium-chain-length PHA formation from canola or avocado oil at different arabinose concentrations was investigated. The functional activity of fadEE.c led to obtaining higher biomass and PHA concentrations compared to the cultures without expressing the gene. While high transcriptional levels of phaJ1P.p, at 0.1% of arabinose, aid the wild-type synthase to polymerize larger-side chain monomers, such as 3-Hydroxyoctanoate (3HO) and 3-Hydroxydecanoate (3HD). The presence of even small amounts of 3HO and 3HD in the co-polymers significantly depresses the melting temperature of the polymers, compared to those composed of pure 3-hydroxybutyrate (3HB). Our data presents supporting evidence that the synthesis of larger-side chain monomers by the recombinant strain relies not only upon the affinity of the wild-type synthase but also on the functionality of the intermediate supplying enzymes.

Functional characterization of a novel thermophilic exo-arabinanase from Thermothielavioides terrestris.

Arabinanases from glycoside hydrolase family GH93 are enzymes with exo-activity that hydrolyze the α-1,5 bonds between arabinose residues present on arabinan. Currently, several initiatives aiming to use byproducts rich in arabinan such as pectin and sugar beet pulp as raw material to produce various compounds of interest are being developed. However, it is necessary to use robust enzymes that have an optimal performance under pH and temperature conditions used in the industrial processes. In this work, the first GH93 from the thermophilic fungus Thermothielavioides terrestris (Abn93T) was heterologously expressed in Aspergillus nidulans, purified and biochemically characterized. The enzyme is a thermophilic glycoprotein (optimum activity at 70 °C) with prolonged stability in acid pHs (4.0 to 6.5). The presence of glycosylation affected slightly the hydrolytic capacity of the enzyme, which was further increased by 34% in the presence of 1 mM CoCl2. Small-angle X-ray scattering results show that Abn93T is a globular-like-shaped protein with a slight bulge at one end. The hydrolytic mechanism of the enzyme was elucidated using capillary zone electrophoresis and molecular docking calculations. Abn93T has an ability to produce (in synergism with arabinofuranosidases) arabinose and arabinobiose from sugar beet arabinan, which can be explored as fermentable sugars and prebiotics. KEY POINTS: • Thermophilic exo-arabinanase from family GH93 • Molecular basis of arabinan depolymerization.

mCherry fusions enable the subcellular localization of periplasmic and cytoplasmic proteins in Xanthomonas sp.

Fluorescent markers are a powerful tool and have been widely applied in biology for different purposes. The genome sequence of Xanthomonas citri subsp. citri (X. citri) revealed that approximately 30% of the genes encoded hypothetical proteins, some of which could play an important role in the success of plant-pathogen interaction and disease triggering. Therefore, revealing their functions is an important strategy to understand the bacterium pathways and mechanisms involved in plant-host interaction. The elucidation of protein function is not a trivial task, but the identification of the subcellular localization of a protein is key to understanding its function. We have constructed an integrative vector, pMAJIIc, under the control of the arabinose promoter, which allows the inducible expression of red fluorescent protein (mCherry) fusions in X. citri, suitable for subcellular localization of target proteins. Fluorescence microscopy was used to track the localization of VrpA protein, which was visualized surrounding the bacterial outer membrane, and the GyrB protein, which showed a diffused cytoplasmic localization, sometimes with dots accumulated near the cellular poles. The integration of the vector into the amy locus of X. citri did not affect bacterial virulence. The vector could be stably maintained in X. citri, and the disruption of the α-amylase gene provided an ease screening method for the selection of the transformant colonies. The results demonstrate that the mCherry-containing vector here described is a powerful tool for bacterial protein localization in cytoplasmic and periplasmic environments.

Mucilaginous Secretions in the Xylem and Leaf Apoplast of the Swamp Palm Mauritia flexuosa L.f. (Arecaceae).

Mauritia flexuosa palms inhabit wetland environments in the dry, seasonal Brazilian savanna (Cerrado) and produce mucilaginous secretions in the stem and petiole that have a medicinal value. The present study sought to characterize the chemical natures of those secretions and to describe the anatomical structures involved in their synthesis. Chemical analyzes of the secretions, anatomical, histochemical analyses, and electron microscopy studies were performed on the roots, stipes, petioles, and leaf blades. Stipe and petiole secretions are similar, and rich in cell wall polysaccharides and pectic compounds such as rhamnose, arabinose, xylose, mannose, galactose, and glucose, which are hydrophilic largely due to their hydroxyl and carboxylate groups. Mucilaginous secretions accumulate in the lumens of vessel elements and sclerenchyma fibers of the root, stipe, petiole, and foliar veins; their synthesis involves cell wall loosening and the activities of dictyosomes. The outer faces of the cell walls of the parenchyma tissue in the mesophyll expand to form pockets that rupture and release pectocellulose substances into the intercellular spaces. The presence of mucilage in the xylem, extending from the roots to the leaf veins and continuous with the leaf apoplast, and sub-stomatal chambers suggest a strategy for plant water economy.

Prospecting for L-arabinose/D-xylose symporters from Pichia guilliermondii and Aureobasidium leucospermi.

With the strong trend toward sustainable technologies, such as the gradual substitution of fossil fuel consumption, improvement in the utilization of sugars from lignocellulosic biomass appears to be an alternative for bioenergy. However, from a number of C5 sugars, few are used in fermentative processes for ethanol production. One of the reasons is because wild-type Saccharomyces cerevisiae is unable to efficiently co-utilize hexoses and pentoses via specific transporters for each type of sugar. Thus, a system of pentose uptake that is not modulated by D-glucose is required. Here, we were able to identify the presence of sugar/H+ symporters for D-xylose and L-arabinose, especially for Pichia guilliermondii, where an uptake of D-glucose via symporter was not detected. The best D-xylose uptake route in P. guilliermondii exhibited a KM of 48 mM and VMAX of 0.48 mmol h-1 g-1 at the early stationary phase (24 h). For L-arabinose, the best route of uptake exhibited a KM of 109 mM and VMAX of 0.8 mmol h-1 g-1 on log phase (12 h). The highest kinetic uptake was observed when the final pH of the medium was below 7. In general, an alkaline medium limited the expression of symporters. The results obtained in this study will help in the further investigation of these symporters through their overexpression in engineered S. cerevisiae.

Morphological bases for intestinal paracellular absorption in bats and rodents.

Flying mammals present unique intestinal adaptations, such as lower intestinal surface area than nonflying mammals, and they compensate for this with higher paracellular absorption of glucose. There is no consensus about the mechanistic bases for this physiological phenomenon. The surface area of the small intestine is a key determinant of the absorptive capacity by both the transcellular and the paracellular pathways; thus, information about intestinal surface area and micro-anatomical structure can help explain differences among species in absorptive capacity. In order to elucidate a possible mechanism for the high paracellular nutrient absorption in bats, we performed a comparative analysis of intestinal villi architecture and enterocyte size and number in microchiropterans and rodents. We collected data from intestines of six bat species and five rodent species using hematoxylin and eosin staining and histological measurements. For the analysis we added measurements from published studies employing similar methodology, making in total a comparison of nine species each of rodents and bats. Bats presented shorter intestines than rodents. After correction for body size differences, bats had ~41% less nominal surface area (NSA) than rodents. Villous enhancement of surface area (SEF) was ~64% greater in bats than in rodents, mainly because of longer villi and a greater density of villi in bat intestines. Both taxa exhibited similar enterocyte diameter. Bats exceeded rodents by ~103% in enterocyte density per cm2 NSA, but they do not significantly differ in total number of enterocytes per whole animal. In addition, there is a correlation between SEF and clearance per cm2 NSA of L-arabinose, a nonactively transported paracellular probe. We infer that an increased enterocyte density per cm2 NSA corresponds to increased density of tight junctions per cm2 NSA, which provides a partial mechanistic explanation for understanding the high paracellular absorption observed in bats compared to nonflying mammals.

Pentoses Used in Cultures of Synechococcus nidulans and Spirulina paracas: Evaluation of Effects in Growth and in Content of Proteins and Carbohydrates

Abstract The biological assimilation of the sugars present in lignocellulosic residues has gained prominence since these residues are the most abundant and economic residues in nature. Thus, the objective of this work was to determine whether the use of D-xylose and L-arabinose as sources of carbon in Synechococcus nidulans and Spirulina paracas cultures affects the growth and production of proteins and carbohydrates. Kinetic growth parameters, pentose consumption, protein content and carbohydrates were evaluated. Synechococcus nidulans and Spirulina paracas consumed all concentrations of pentose used. The highest cellular concentration (1.37 g.L-1) and the highest protein productivity (54 mg.L-1.d-1) were obtained for Spirulina paracas, which was submitted to the addition of 38.33 mg.L-1 D-xylose and 1.79 mg.L-1 L-arabinose. The use of pentose promoted the accumulation of proteins for the studied microalgae. This is one of the first works to report protein bioaccumulation as a result of pentose addition.

Production optimization, purification, expression, and characterization of a novel α-L-arabinofuranosidase from Paenibacillus polymyxa

Background: α-L-Arabinofuranosidase (EC 3.2.1.55) catalyzes the hydrolysis of terminal α-L-1,2-, -1,3-, and -1,5- arabinofuranosyl residues in arabinose-containing polymers, and hence, it plays an important role in hemicellulose degradation. Herein, the bacterium Paenibacillus polymyxa, which secretes arabinofuranosidase with high activity, was selected for enzyme production, purification, and characterization. Results: Medium components and cultural conditions were optimized by the response surface method using shake flask cultures. Arabinofuranosidase production reached 25.2 U/mL under optimized conditions, which were pH 7.5, 28°C, and a basic medium supplemented with 1.5 g/L mannitol and 3.5 g/L soymeal. Furthermore, the arabinofuranosidase secreted by P. polymyxa, named as PpAFase-1, was partially purified from the supernatant using a DEAE Sepharose Fast Flow column and a hydroxyapatite column. The approximate molecular mass of the purified PpAFase-1 was determined as 56.8 kDa by SDS-PAGE. Protein identification by mass spectrometry analysis showed that the deduced amino acid sequence had significant similarity to the glycosyl hydrolase family 51. The deduced gene of 1515 bp was cloned and expressed in Escherichia coli BL21 (DE3) cells. Purified recombinant PpAFase-1 was active toward p-nitrophenyl-α-L-arabinofuranoside (pNPAraf). The Km and kcat values toward pNPAraf were 0.81 mM and 53.2 s−1 , respectively. When wheat arabinoxylan and oat spelt xylan were used as substrates, PpAFase-1 showed poor efficiency. However, a synergistic effect was observed when PpAFase-1 was combined with xylanase from Thermomyces lanuginosus. Conclusion: A novel GH51 enzyme PpAFase-1 was cloned from the genome of P. polymyxa and expressed in E. coli. This enzyme may be suitable for hemicellulose degradation on an industrial scale.

Chemical characterization and complement modulating activities of an arabinogalactan-protein-rich fraction from an aqueous extract of avocado leaves.

The aim of this study was to chemically characterize an arabinogalactan-protein-rich fraction (FRAGP) obtained from an aqueous extract of avocado leaves and investigate its effects on the classical pathway of the complement system. The FRAGP contained 4.6% ±â€¯1.8%, 22.5% ±â€¯4.9%, and 76.7% ±â€¯8.8% of total protein, arabinogalactan-protein, and carbohydrates, respectively. Arabinose and galactose were the main monosaccharide constituents. FT-IR and NMR data, together with linkage analyses, indicated the presence of a structure that included a (1 → 3)-linked ß-D-Galp main chain, mainly substituted at O-6 by Gal and Ara residues, which was characteristic of a type II arabinogalactan. The effect of FRAGP on the classical pathway of complement system was examined by a hemolytic fixation test and comparing with heparin, which was used as a control for inhibition. With pre-incubation, the IC50 of FRAGP was 1.90 ±â€¯1.1 µg/mL, which was similar to that of heparin (IC50 = 2.90 ±â€¯0.3 µg/mL). Without pre-incubation, the IC50 values were 18.6 ±â€¯3.7 and 8.0 ±â€¯4.1 µg/mL for FRAGP and heparin, respectively. Collectively, these results suggested that FRAGP has an inhibitory effect on the classical pathway of the complement system.

Small intestinal epithelial permeability to water-soluble nutrients higher in passerine birds than in rodents.

In the small intestine transcellular and paracellular pathways are implicated in water-soluble nutrient absorption. In small birds the paracellular pathway is quantitatively important while transcellular pathway is much more important in terrestrial mammals. However, there is not a clear understanding of the mechanistic underpinnings of the differences among taxa. This study was aimed to test the hypothesis that paracellular permeability in perfused intestinal segments is higher in passerine birds than rodents. We performed in situ intestinal perfusions on individuals of three species of passerine birds (Passer domesticus, Taeniopygia guttata and Furnarius rufus) and two species of rodents (Mus musculus and Meriones ungiculatus). Using radio-labelled molecules, we measured the uptake of two nutrients absorbed by paracellular and transcellular pathways (L-proline and 3-O-methyl-D-glucose) and one carbohydrate that has no mediated transport (L-arabinose). Birds exhibited ~2 to ~3 times higher L-arabinose clearance per cm2 epithelium than rodents. Moreover, paracellular absorption accounted for proportionally more of 3-O-methyl-D-glucose and L-proline absorption in birds than in rodents. These differences could be explained by differences in intestinal permeability and not by other factors such as increased retention time or higher intestinal nominal surface area. Furthermore, analysis of our results and all other existing data on birds, bats and rodents shows that insectivorous species (one bird, two bats and a rodent) had only 30% of the clearance of L-arabinose of non-insectivorous species. This result may be explained by weaker natural selection for high paracellular permeability in animal- than in plant-consumers. Animal-consumers absorb less sugar and more amino acids, whose smaller molecular size allow them to traverse the paracellular pathway more extensively and faster than glucose.

Innovative polyhydroxybutyrate production by Chlorella fusca grown with pentoses.

The current study aimed to evaluate if the addition of pentoses along with variations in light intensity and photoperiod can stimulate the production of polyhydroxybutyrate (PHB) and other biomolecules by Chlorella fusca LEB 111. The variables evaluated were the addition of xylose and arabinose as sources of organic carbon, different photoperiods (18 h, 12 h and 6 h light) and variations in light intensities (58, 28 and 9 µmolphotons m-2 s-1). The highest PHB accumulation (17.4% w w-1) and protein production (53.2% ww-1) were observed in assays with xylose addition and a photoperiod of 6 h of light provided at 28 and 58 µmolphotons m-2 s-1, respectively. The highest lipid content (24.7% w w-1) was obtained with 18 h of light. The current study contributes to the development of sustainable alternatives for the use of wastes and the production of biomolecules from algae.

Arabinogalactan from edible jambo fruit induces different responses on cytokine secretion by THP-1 macrophages in the absence and presence of proinflammatory stimulus.

Syzygium jambos is an Indo-Malaian found in many tropical countries and it is mainly composed of carbohydrates. Fraction PF-WSP and SF-WSP were obtained by aqueous extraction followed by Fehling's treatment. Monosaccharide analysis showed that fraction PF-WSP has a high content of uronic acids (90%) and fraction SF-WSP presented mainly galactose (39.1%) and arabinose (34.2%), as neutral sugars and 9% of galacturonic acid. The presence of type II arabinogalactan in SF-WSP was evidenced by methylation analysis and 13C/1H HSQC NMR experiments. Immunomodulating properties of SF-WSP was investigated. It decreases THP-1 macrophage viability at the highest concentration tested (200µg/mL). We then tested non-cytotoxic concentrations of SF-WSP on THP-1 cytokine production in the presence and absence of LPS. The results showed that SF-WSP increased TNF-α, IL-1ß and IL-10 secretion in a concentration-dependent manner as well as attenuated the inflammatory response induced by LPS at the highest concentration (100µg/mL). These results contribute to elucidate the effects of fruit pectic polysaccharides on immune cells.

Rheology and microstructure of gels based on wheat arabinoxylans enzymatically modified in arabinose to xylose ratio.

BACKGROUND: Arabinoxylans (AX) are polysaccharides consisting of a backbone of xyloses with arabinose substituents ester-linked to ferulic acid (FA). The arabinose to xylose ratio (A/X) in AX may vary from 0.3 to 1.1. AX form covalent gels by cross-linking of FA but physical interactions between AX chains also contribute to the network formation. The present study aimed to investigate the rheological and microstructural characteristics of gels based on AX enzymatically modified in A/X. RESULTS: Tailored AX presented A/X ranging from 0.68 to 0.51 and formed covalent gels. Dimers of FA content and elasticity (G') increased from 0.31 to 0.39 g kg-1 AX and from 106 to 164 Pa when the A/X in the polysaccharide decreased from 0.68 to 0.51. Atomic force microscopy images of AX gels showed a sponge-like microstructure at A/X = 0.68, whereas, at lower values, gels presented a more compact microstructure. Scanning electron microscopy analysis of AX gels show an arrangement of different morphology, passing from an imperfect honeycomb (A/X = 0.68) to a flake-like microstructure (A/X = 0.51). CONCLUSION: Lower A/X values favor the aggregation of AX chains resulting in an increase in di-FA content, which improves the rheological and microstructural characteristics of the gel formed. © 2017 Society of Chemical Industry.

Extraction of Glucuronoarabinoxylan from Quinoa Stalks (Chenopodium quinoa Willd.) and Evaluation of Xylooligosaccharides Produced by GH10 and GH11 Xylanases.

Byproducts from quinoa are not yet well explored sources of hemicellulose or products thereof. In this work, xylan from milled quinoa stalks was retrieved to 66% recovery by akaline extraction using 0.5 M NaOH at 80 °C, followed by ethanol precipitation. The isolated polymer eluted as a single peak in size-exclusion chromatography with a molecular weight of >700 kDa. Analysis by Fourier transform infrared spectroscopy and nuclear magnetic resonance (NMR) combined with acid hydrolysis to monomers showed that the polymer was built of a backbone of ß(1 → 4)-linked xylose residues that were substituted by 4-O-methylglucuronic acids, arabinose, and galactose in an approximate molar ratio of 114:23:5:1. NMR analysis also indicated the presence of α(1 → 5)-linked arabinose substituents in dimeric or oligomeric forms. The main xylooligosaccharides (XOs) produced after hydrolysis of the extracted glucuronoarabinoxylan polymer by thermostable glycoside hydrolases (GHs) from families 10 and 11 were xylobiose and xylotriose, followed by peaks of putative substituted XOs. Quantification of the unsubstituted XOs using standards showed that the highest yield from the soluble glucuronoarabinoxylan fraction was 1.26 g/100 g of xylan fraction, only slightly higher than the yield (1.00 g/100 g of xylan fraction) from the insoluble fraction (p < 0.05). No difference in yield was found between reactions in buffer or water (p > 0.05). This study shows that quinoa stalks represent a novel source of glucuronoarabinoxylan, with a substituent structure that allowed for limited production of XOs by GH10 or GH11 enzymes.