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The red prickly pear fruit (Opuntia ficus-indica L. Mill), endemic from Mexico's semi-desert regions and present in North Africa and Southern Europe, particularly Italy and Spain, is a valuable source of nutrients, bioactive compounds, and polysaccharides. This study used non-destructive techniques like microscopy and Raman and infrared (IR) spectroscopy to characterize polysaccharides extracted from two red prickly pear varieties. The polysaccharides constitute approximately 80% of the peel and 39–18% of the pulp; microscopy provided insights into its microstructural details, while Raman and IR spectroscopy enabled the identification of its specific functional groups. The results revealed distinct microstructural attributes: mucilage displays a microstructure influenced by the ratio of acidic to neutral sugar monomers; pectin exhibits a low degree of methoxylation alongside a characteristic egg-box structure facilitated by calcium ions; hemicellulose presents a delicate, porous layer; and cellulose reveals a layered microstructure supported by thin or robust fibers and calcium crystals. The functional groups identified via Raman and IR spectroscopy provided specific information that could be used to infer chemical interactions influenced by functional groups like hydroxyl, carboxyl, and methyl, suggesting potential binding, stabilization, and water retention properties that enhance their utility as functional ingredients in food products. These findings, obtained using non-destructive methods, enhance the understanding of the compositional and microstructural characteristics of polysaccharides in the red prickly pear, which, in turn, can be used to predict their promising technological applications as functional ingredients. [ABSTRACT FROM AUTHOR]

The red prickly pear fruit (Opuntia ficus-indica L. Mill), endemic from Mexico’s semi-desert regions and present in North Africa and Southern Europe, particularly Italy and Spain, is a valuable source of nutrients, bioactive compounds, and polysaccharides. This study used non-destructive techniques like microscopy and Raman and infrared (IR) spectroscopy to characterize polysaccharides extracted from two red prickly pear varieties. The polysaccharides constitute approximately 80% of the peel and 39–18% of the pulp; microscopy provided insights into its microstructural details, while Raman and IR spectroscopy enabled the identification of its specific functional groups. The results revealed distinct microstructural attributes: mucilage displays a microstructure influenced by the ratio of acidic to neutral sugar monomers; pectin exhibits a low degree of methoxylation alongside a characteristic egg-box structure facilitated by calcium ions; hemicellulose presents a delicate, porous layer; and cellulose reveals a layered microstructure supported by thin or robust fibers and calcium crystals. The functional groups identified via Raman and IR spectroscopy provided specific information that could be used to infer chemical interactions influenced by functional groups like hydroxyl, carboxyl, and methyl, suggesting potential binding, stabilization, and water retention properties that enhance their utility as functional ingredients in food products. These findings, obtained using non-destructive methods, enhance the understanding of the compositional and microstructural characteristics of polysaccharides in the red prickly pear, which, in turn, can be used to predict their promising technological applications as functional ingredients.

Cyanobacterium sp. IPPAS B-1200 is a cyanobacteria strain that belongs to the rare genus Cyanobacterium, family Cyanobacteriaceae fam. nov. Studies devoted to the isolation of secondary metabolites from this strain concentrate mostly on the fatty acid composition while the issue of isolating and identifying exopolysaccharides remains understudied. However, polysaccharides from cyanobacteria are of scientific and economic interest in the framework of biotechnology, medicine, pharmacology, etc. The research objective was to study the effect of the physicochemical conditions of cultivation and the composition of the cultural medium on exopolysaccharide production. Cyanobacterium sp. B-1200 were grown under 7500 ± 50 lux (12 h light/12 h dark). The dry cell weight was determined by gravimetry and a calibration plot that illustrated the dependence of the biomass amount on the degree of absorption at a wavelength of 750 nm. The amount of polysaccharides in the culture liquid was assessed by the Anthrone-sulphate method. The extraction was carried out by alcohol precipitation. The method of ultrasonic dispersion was used to destroy the cell walls of cyanobacteria. The experimental study revealed the optimal parameters for the extraction and purification of exopolysaccharides from the culture medium. Removal of sodium bicarbonate from the medium and a 300%-increase in its concentration raised the yield of polysaccharides. The optimal value of active acidity for the synthesis of polysaccharides was pH = 6 while the optimal temperature for their accumulation was 35°C. The largest amount of biomass was obtained at 25°C. Intense white illumination contributed to the greatest release of exopolysaccharides into the culture medium; red-white illumination affected the morphology of cyanobacteria cells. During the extraction, the concentration, temperature, and nature of the extractant proved to be the most important factors. For example, isopropanol produced the highest yield while butanol triggered the least effective response. The optimal extraction and purification modes for polysaccharides were as follows. For ultrasonic processing, the best results were obtained at a power of 20 W after 5 min. For freeze drying, the rational parameters were 8 h at –15°C.

The alcohol-insoluble residue in Vanilla dressleri, V. odorata, V. planifolia and V. pompona mature leaves was fractionated into water-, oxalate-, HCl- and NaOH-soluble pectins, hemicellulose and lignocellulose. Neutral sugars and uronic acids of each fraction were determined by high-performance anion exchange chromatography-pulsed amperometric detection. V. dressleri differentiated from the other three species based on the higher amounts of the HCl-soluble pectin fraction and the amount of glucose exceeding 5–7 times the values found in the NaOH-soluble pectin fraction in the other species, as well as a cellulose/hemicellulose ratio of ca. 2/3. Analogously, V. planifolia could also be distinguished by its higher cellulose/hemicellulose ratio of ca. 7. In addition to taxonomical implications, these results might be instrumental for defining adequate conditions for cell wall digestion aiming at protoplast isolation and appropriate media composition for cell wall regeneration during protoplast culture, which has been elusive in the Orchidaceae.

Vischeria punctata is a unicellular microalga that has industrial potential, as it can produce substances with beneficial properties. Among them, endopolysaccharides (accumulated in cells) and exopolysaccharides (released by cells into the culture medium) are of particular interest. This study aimed to investigate the effect of nutrient medium composition on the growth of V. punctata biomass and the synthesis of polysaccharides by microalgae. The effect of modifying a standard nutrient medium and varying cultivation parameters (temperature, time, and extractant type) on the yield of exopolysaccharides produced by the microalgae V. punctate was investigated. The methods of spectrophotometry, ultrasonic extraction, and alcohol precipitation were used in the study. It was found that after 61 days of cultivation, the concentration of polysaccharides in the culture medium was statistically significantly higher (p <0.05) when using a Prat nutrient medium (984.9 mg/g d.w.) than BBM 3N (63.0 mg/g d.w.). It was found that the increase in the V. punctata biomass when cultivated on different nutrient media did not differ significantly. The maximum biomass values on Prat and BBM 3N media were 1.101 mg/g d.w. and 1.120 mg/g d.w., respectively. Neutral sugars and uronic acids were found in the culture media. It follows on from the obtained data that the modified PratM medium was more efficient for extracting polysaccharides from V. punctata. The potential of microalgae as new sources of valuable chemicals (polysaccharides), which can be widely used in technologies for developing novel functional foods, biologically active food supplements, and pharmaceutical substances, was studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesis of polysaccharides from six Chlorella strains was studied. • Two of the Chlorella strains studied had higher polysaccharide productivity. • C. kessleri produced more neutral sugars than the studied strains. • C. sorokiniana produced more uronic acids than the strains studied. Microalgae are known to be the richest natural source of polysaccharides. The study aimed to evaluate the ability of microalgae from the Chlorella sp. genus to synthesize polysaccharides. Brody & Emerson max medium proved to be the most effective; the average cell content in the culture fluid at the beginning and at the end of cultivation for IPPAS Chlorella pyrenoidosa Chick was 1.23 ± 0.03 g/L and 1.71 ± 0.20 g/L, respectively. With a high average dry weight of IPPAS Chlorella pyrenoidosa Chick (4.45 ± 0.10 g/L), it produced the least amount of neutral sugars (0.75 ± 0.02 g/L) and uronic acids (0.14 ± 0.01 mg/L). The microalga IPPAS Chlorella vulgaris with the lowest average dry weight (1.18 ± 0.03 g/L) produced 0.80 ± 0.02 g/L of neutral sugars and 0.17 ± 0.01 mg/L of uronic acids. Microalgal polysaccharides have the potential to be used as a source for biologically active food additives, as they contain various types of polysaccharides that can be beneficial to human health. [ABSTRACT FROM AUTHOR]

Amino acids (AA) and carbohydrates (CHO) are important components of the marine organic carbon cycle. Produced mainly by phytoplankton as part of the particulate organic carbon (POC) fraction, these compounds can be released into the outer medium where they become part of the dissolved organic carbon (DOC) pool and are rapidly taken up by heterotrophs (e.g., bacteria). We investigated the quantity and quality of POC and DOC, AA and CHO composition in both pools in three different water masses in the Fram Strait (Arctic Ocean) in summer 2017. Polar Waters and Atlantic Waters showed similar concentrations of particulate and dissolved AA and CHO, despite Polar Waters showing the highest DOC concentrations. In Mixed Waters, where the two water masses mix with each other and with melting sea ice, the concentrations of particulate and dissolved AA and CHO were highest. AA and CHO composition differed substantially between the particulate and dissolved fractions. The particulate fraction (>0.7 μm) was enriched in essential AA and the CHO galactose, xylose/mannose, and muramic acid. In the dissolved fraction non-essential AA, several neutral CHO, and acidic and amino CHO were enriched. We further investigated different size fractions of the particulate matter using a separate size fractionation approach (0.2–0.7 μm, 0.7–10 μm and >10 μm). The chemical composition of the 0.2–0.7 μm size-fraction had a higher contribution of non-essential AA and acidic and amino sugars, setting them apart from the 0.7–10 μm and >10 μm fractions, which showed the same composition. We suggest that the relative differences observed between different size fractions and DOC with regards to AA and CHO composition can be used to evaluate the state of organic matter processing and evaluate the contribution of autotrophic phytoplankton or more heterotrophic biomass. In the future, changing conditions in the Central Arctic Ocean (Atlantification, warming, decreasing ice concentrations) may increase primary production and consequently degradation. The AA and CHO signatures left behind after production and/or degradation processes occurred, could be used as tracers after the fact to infer changes in microbial loop processes and food web interactions.

The gel formation behaviour of green jelly leaf (GJL) pectins isolated by using water extraction method with extraction temperatures of 45, 65, 85 and 95 °C was investigated. The isolated pectins were also analysed for the yield, physicochemical and functional properties. The yield, molecular weight ( M w ) and galacturonic acid content varied from ∼10 to 13% w/w, 3 × 10 5 to 12 × 10 5  g/mol and ∼75–86% w/w, respectively. Gelation of GJL pectins was a cold-setting gel and could be induced by acid and/or divalent ions; however, the latter gelation method showed a lesser temperature dependence than acid-induced gel. The addition of NaCl had enhanced the gel structure due to electrostatic screening effect. The mechanical spectra response showed that GJL pectin was typically gel-like with G′ greater than G″ and strongly influenced by pH and calcium concentration. The variation in pectin gel structures was also attributed to difference in pectin physicochemical properties particularly the degree of esterification (DE). Furthermore, lower DE pectins with higher charge values exhibited a stronger gel like properties with less variation on mechanical spectrum compared to higher DE pectins. These findings showed considerable potential of GJL pectin as a thickener and gelling agent and could be useful for development of low-sugar and high calcium content food with different textures. [ABSTRACT FROM AUTHOR]

Abstract: Perennial bioenergy crops accumulate carbon (C) in soils through minimally disturbing management practices and large root inputs, but the mechanisms of microbial control over C dynamics under bioenergy crops have not been clarified. Root‐derived C inputs affect both soil microbial contribution to and degradation of soil organic matter resulting in differing soil organic carbon (SOC) concentrations, storage, and stabilities under different vegetation regimes. Here, we measured biomarker amino sugars and neutral sugars and used diffuse reflectance mid‐infrared Fourier transform spectroscopy (DRIFTS) to explore microbial C contributions, degradation ability, and SOC stability, respectively, under four potential bioenergy crops, M.×giganteus (Miscanthus × giganteus), switchgrass (Panicum virgatum L.), a mixed prairie, and a maize (Zea mays L.)–maize–soybean (Glycine max(L.) Merr.) (MMS) rotation over six growing seasons. Our results showed that SOC concentration (g/kg) increased by 10.6% in mixed prairie over the duration of this experiment and SOC storage (Mg/ha) increased by 17.0% and 15.6% in switchgrass and mixed prairie, respectively. Conversion of row crops to perennial grasses maintained SOC stability and increased bacterial residue contribution to SOC in M.×giganteus and switchgrass by 20.0% and 15.0%, respectively, after 6 years. Degradation of microbe‐derived labile SOC was increased in M.×giganteus, and degradation of both labile and stable SOC increased in MMS rotation. These results demonstrate that microbial communities under perennial grasses maintained SOC quality, while SOC quantity increased under switchgrass and mixed prairie. Annual MMS rotation displayed decreases in aspects of SOC quality without changes in SOC quantity. These findings have implications for understanding microbial control over soil C quantity and quality under land‐use shift from annual to perennial bioenergy cropping systems. [ABSTRACT FROM AUTHOR]

‘Friar’ plum ( Prunus salicina Lindl.) fruit were stored at low (0 °C), intermediate (5 and 15 °C) and ambient temperature (25 °C). Flesh translucency was evidenced as the main chilling injury (CI) symptom and the CI developed rapidly at 5 and 15 °C but suppressed at 0 °C. Modifications of cell wall pectin in ‘Friar’ plums were investigated during storage. Sodium carbonate-soluble pectin (SSP) was found to be predominant in the fruit but it decreased more rapidly at 5 and 15 °C than 0 °C. Nevertheless, SSP possessed abundant galactose, arabinose and rhamnose at 5 and 15 °C. Nanostructural observations indicated that the detachment and degradation of linear backbone chains in SSP molecules were enhanced at 5 and 15 °C. Therefore, the development of CI of ‘Friar’ plums at intermediate temperatures was associated with the modifications of SSP in the cell wall pectin of the fruit subjected to chilling stress. [ABSTRACT FROM AUTHOR]

As crucial carbon (C) and energy sources for soil microorganisms, neutral sugars are essential component of the labile soil organic carbon (SOC) pool derived from plants and microorganisms and can directly affect the accumulation of SOC. However, the changes in labile SOC components with elevated soil nitrogen (N) and phosphorus (P) inputs remain unclear. Taking advantage of a 10-year field N and P addition experiment in an alpine grassland on the Tibetan Plateau, we analyzed the compositions and concentrations of neutral sugar in plant versus soil, coupled with soil nutrient properties and plant biomass, we assessed factors affecting the preservation of neutral sugars in soil. We found that the concentrations of neutral sugar were lower in plant shoots than those in roots. The concentrations of neutral sugar and the GM/AX ratio (GM: galactose and mannose; AX: arabinose and xylose) in shoots and roots were insensitive to nutrient addition. The concentrations of neutral sugar in the topsoil were significantly lower than those in the subsoil, and both significantly decreased with N alone and P alone addition. The GM/AX ratio was significantly higher in the topsoil than that in the subsoil and both increased with nutrient addition (except for NP addition in the topsoil). Additionally, SOC was negatively correlated with soil neutral sugar concentrations but positively correlated with the GM/AX ratio. This result emphasizes the important role of microbial transformation of neutral sugars in regulating the relative magnitude of the labile SOC pool versus the stable SOC pool, which is consistent with the concept of "microbial carbon pump" (MCP). This study demonstrates differential compositions and concentrations, as well as responses of neutral sugars to N and P addition in plant versus soil, providing new information to understand the effect of nutrient addition on the SOC pool in the plant-soil system. [Display omitted] • Neutral sugar in shoots and roots was insensitive to N and P addition. • Neutral sugar in the top- and subsoil both declined with N or P alone addition. • The GM/AX did not change in plant but increased in soil with N or P alone addition. • Neutral sugar was negatively correlated with SOC. [ABSTRACT FROM AUTHOR]

This work aimed to characterize compositional and bioactive features of Aloe vera leaf (fillet, mucilage, and rind) and flower. The edible fillet was analysed for its nutritional value, and all samples were studied for phenolic composition and antioxidant, anti-inflammatory, antimicrobial, tyrosinase inhibition, and cytotoxic activities. Dietary fibre (mainly mannan) and available carbohydrates (mainly free glucose and fructose) were abundant macronutrients in fillet, which also contained high amounts of malic acid (5.75 g/100 g dw) and α-tocopherol (4.8 mg/100 g dw). The leaf samples presented similar phenolic profiles, with predominance of chromones and anthrones, and the highest contents were found in mucilage (131 mg/g) and rind (105 mg/g) extracts, which also revealed interesting antioxidant properties. On the other hand, the flower extract was rich in apigenin glycoside derivatives (4.48 mg/g), effective against Pseudomonas aeruginosa (MIC = 0.025 mg/mL and MBC = 0.05 mg/mL) and capable of inhibiting the tyrosinase activity (IC50 = 4.85 mg/mL). The fillet, rind, and flower extracts also showed a powerful antifungal activity against Aspergillus flavus, A. niger, Penicillium funiculosum, and Candida albicans, higher than that of ketoconazole. Thus, the studied Aloe vera samples displayed high potential to be exploited by the food or cosmetic industries, among others.

Increased watermelon fruit flesh firmness is systematically incurred with grafting on Cucurbita hybrid rootstocks (heterografting). Possible differences in mesocarp cell wall constitution and histology between heterografted, homeografted (self-grafted) and non-grafted watermelon were examined, as well as their contributions to fruit texture. Firmness correlated positively ( r = 0.78, p < 0.001) with cell density (cells mm −2 ) which was higher in heterografts (5.83) than homeografts (4.64) and non-grafted controls (4.69). Mean cell size was smallest in heterografts and correlated negatively ( r = −0.75, p < 0.001) with firmness. Cell wall material, particularly the water-insoluble pectin fractions associated with firmness, were highest in heterografts. No associations with firmness were found for cell wall neutral sugars and membrane permeability. Higher parenchymatic cell density with higher content of alcohol insoluble residue and more abundant water-insoluble pectin fractions underscore enhanced firmness in heterografts. Possible implication of osmolytes in rootstock-mediated cell pressure regulation warrants further investigation. [ABSTRACT FROM AUTHOR]

Yeast mannan treatments effectively delayed colour change and firmness decline and inhibited ethylene production in two cultivars of tomato fruit during storage. The yeast mannan treatment maintained the integrity of tomato pericarp cell wall architecture and suppressed the modification of water-soluble and insoluble pectic polysaccharides in the cell wall. A decrease in the neutral sugars, including d -galactose, l -arabinose and l -rhamnose, in water-insoluble pectin and an increase in these sugars in water-soluble pectin were inhibited by yeast mannan. The contents of d -xylose and d -mannose in the hemicellulose fraction were significantly higher in the yeast mannan-treated fruit after storage. The activities of several cell wall-modifying enzymes, including pectinmethylesterase, polygalacturonase and β-galactosidase, were suppressed in fruit treated with yeast mannan during storage. Overall, the yeast mannan-induced delay in the ripening progress of tomato fruit might occur via the strong suppression of ethylene synthesis, causing inhibition of solubilization and depolymerization of cell wall polysaccharides. [ABSTRACT FROM AUTHOR]

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Both forest-floor litter and roots are known to be involved in the formation of soil organic carbon (SOC), but it remains elusive how the two contrasting types of plant carbon sources would differentiate in their effects on SOC. Here we used field-based soil mesocosms to study the responses of SOC components (i.e. mineral-associated organic C [MAOC], particulate organic C [POC], and dissolved organic C [DOC]) and pathways of production (i.e. plant-derived vs. microbial-derived C compounds) to multi-year treatments of forest-floor litter and roots in a temperate oak forest in central China. After eight years, the concentrations of both POC and MAOC were significantly higher in plots with presence of forest-floor litter than in those exclusive of both forest-floor litter and roots at the soil depth of 0–5 cm; roots predominantly affected POC but not the total SOC. The contributions from the forest-floor litter and roots to total SOC and its components were all non-additive; the plots with co-occurrence of forest-floor litter and roots had 49.7% less total SOC, 36.6% less POC, and 54.7% less MAOC, than the sum of the plots with only forest-floor litter or roots, at the soil depth of 0–5 cm. The concentrations of both lignin phenols and microbial biomass carbon (MBC) were significantly higher in plots with only forest-floor litter than in those exclusive of both forest-floor litter and roots down to a depth of 20 cm, and the plant-derived neutral sugars were significantly higher in plots with only forest-floor litter than in those exclusive of both forest-floor litter and roots at the soil depth of 0–10 cm. In contrast, the concentration of lignin phenols was significantly higher in plots with only roots than in those exclusive of both forest-floor litter and roots below the depth of 5 cm, and the concentrations of MBC and microbial-derived neutral sugars were higher in plots with only roots than in those exclusive of both forest-floor litter and roots at the soil depth of 0–10 cm. The plots with co-occurrence of forest-floor litter and roots had a significantly higher concentration of lignin phenols at all soil depths investigated, as well as higher concentrations of the plant- and microbial-derived neutral sugars and MBC at the soil depth of 0–5 cm, than those exclusive of both forest-floor litter and roots; the effects were all non-additive such that the plots with co-occurrence of forest-floor litter and roots had less plant- and microbial-derived C compounds than the sum of the values between the plots with only forest-floor litter and the plots with only roots. The contributions of amino sugars to SOC did not significantly respond to either the treatments with forest-floor litter and roots or soil depth, albeit variable MBC concentrations. In addition, our results show that the microbial-derived neutral sugars were positively correlated with plant-derived neutral sugars. Findings in this study provide empirical evidence on the primacy of forest-floor litter in SOC pool at the soil depth of 0–5 cm, and demonstrate the differential roles and contributions between forest-floor litter and roots in the pathways of SOC formation and spatial differentiation of carbon compounds. [Display omitted] • Forest-floor litter is primary source of SOC in 0–5 cm soil layer. • Roots contributed greatly to POC in surface soil. • Litter and roots are non-additive in forming SOC. • Litter and root inputs differentially affect microbial-vs. plant-derived SOC. • Amino sugars are unresponsive to input C source types. [ABSTRACT FROM AUTHOR]

An awareness of the transformation of plant residues returned to cultivated soils is vital for a better understanding of carbon cycles, the maintenance of soil fertility and the practice of a sustainable agriculture. The transformation of maize ( Zea mays L) straw residues into soil organic matter (SOM) in a one year incubation experiment was studied in a soil that had been under long term cultivation with wheat ( Triticum aestivum L) for > 30 years. A novel sequential exhaustive extraction and fractionation procedure isolated a series of fractions of SOM. The samples were characterized by elemental and δ 13 C analyses, by amino acids and neutral sugars analyses, by Fourier transformed infrared (FTIR) spectrometry, and by solid state 13 C nuclear magnetic resonance (NMR) spectroscopy and with chemical shift anisotropy (CSA) –filter and dipolar dephasing (DD) spectral editing NMR techniques. The δ 13 C data indicated that 59% and 38% of the newly transformed organic carbon was in the humic and fulvic acid fractions, respectively, and in general a greater proportion of the transformed carbon was in the fractions isolated at the higher pH values. Results for SOM fractions from the amended soil indicate dominant contributions from carbohydrate and lignin-like material, and that can be clearly identified by FTIR, CP/TOSS, and spectral editing of CSA-filter and DD. The compositions of the fractions from the amended and non-amended soils fractions can be clearly differentiated using principal component analysis (PCA) for the data collected. The sequential extraction procedure showed that the hydrophilicity of humic fractions increased as the result of the maize amendment, and the aromaticity of the fraction decreased. The data may give some indications of transformations that take place during humification processes. [ABSTRACT FROM AUTHOR]

A polysaccharide from the leaves of Sesamum radiatum was extracted by maceration in deionized water followed by ethanol precipitation then chemically and physically characterised. Monosaccharide composition and linkages were determined by high performance anion exchange chromatography (HPAEC), gas chromatography–mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) spectroscopy respectively. Sesamum gum was composed of glucuronic acid, mannose, galactose, and xylose with trace quantities of glucose, rhamnose and arabinose. Proton and 13 C NMR spectroscopy, and linkage analysis revealed a glucuronomannan based structure comprising a backbone of →4)-β- d -Glc p A-(1 → 2)-α- d -Man p -(1→ with side-chains of galactose and xylose. Hydrated sesamum gum displayed temperature independent viscoelastic properties with no thermal hysteresis. Intrinsic viscosity was determined to be 3.31 and 4.40 dL g −1 in 0.1 M NaCl and deionised water respectively, while the critical concentration was determined to be 0.1% w/v. The characterisation performed in this study will help direct potential applications of this material in foods and pharmaceuticals. [ABSTRACT FROM AUTHOR]

A method using partial least squares (PLS) for simultaneous determination of neutral and uronic sugars was developed in this paper. This method is based on the development of the reaction between the analytes and anthrone. The calibration set was built with 25 binary solutions at the concentrations ranging from 20 to 100 μg/mL for glucose and from 10 to 50 μg/mL for glucuronic acid. An independent prediction set was utilized to check the robustness of the PLS calibration model. The root-mean-square error of prediction (RMSEP) values for neutral and uronic sugars are 1.2233 and 1.9367, respectively. The correlation coefficient for the prediction set ( R p 2 ) values for them are 0.9971 and 0.9767, respectively. Compared with the univariate method, the proposed method improves detection accuracy. In addition, it was also applied to commercial polysaccharides and Glycyrrhiza uralensis polysaccharides (GUPs), and the results indicated that the PLS model was suitable for simultaneous determination of neutral and uronic sugars. [ABSTRACT FROM AUTHOR]

Realizou-se estudo sobre a influência da atmosfera modificada com diferentes concentrações de gases durante o armazenamento de abacaxi cv. Smooth cayennne minimamente processado, por oito dias, à temperatura de 5ºC e 85% de UR. Foram realizadas análises de açúcares neutros, celulose, hemicelulose e poliuronídeos totais na parede celular. O abacaxi minimamente processado foi acondicionado sob duas Atmosferas Modificadas Ativas, uma com 5% de O2 e 5% de CO2 (AM1),outra com 2% de O2 e 10% de CO2 (AM2),e uma Atmosfera Modificada Passiva (Controle) durante 8 dias de armazenamento. O uso de atmosferas modificadas ativas permitiu que o abacaxi minimamente processado sofresse menor degradação da parede celular com menor solubilização das hemiceluloses. Abacaxis minimamente processados e armazenados sob atmosfera modificada obtiveram uma vida de prateleira média de 6 dias, a 5º C.Pineapples minimally processed were, stored eight days (5ºC and 85% RH) under passive and active atmosphere (MA). Neutral sugars, cellulose, hemicellulose, and total polyuronide analysis in cell wall were done. Two different active MA were tested: 5% of O2 + 5% of CO2 (MA1) and 2% of O2 + 10% of CO2 (MA2) and one passive MA (Control); during eight days of storage. Pineapples minimally processed stored under active modified atmosphere showed degradation of cell wall and less solubilization of hemicelluloses, besides being more effective in control of ethanol production and formation of off flavours. Pineapples minimally processed stored under modified atmosphere, showed life average of 6 days under refrigeration at 5ºC.

Microbial necromass comprises a large fraction of soil organic matter (SOM) due to the accumulation and stabilization of microbial residues from dead archaea, bacteria and fungi. Amino sugars, neutral sugars and uronic acids have been used as microbial necromass biomarkers to trace the origin and composition of microbial residues in the SOM pool. Due to the structural complexity of sugars, derivatization reactions and high-throughput analytical methods are required to separate and quantify these sugar-related compounds. Our aim was to develop a rapid and sensitive assay to measure amino sugar, neutral sugar and uronic acid compounds using pre-column 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization. PMP-derivatives were separated and quantified via reversed phase (RP) ultra-high-performance liquid chromatography (UPLC) coupled to high-resolution Orbitrap mass spectrometry (MS). The method was validated and applied on hydrolyzed peptidoglycans and the biomass of archaeal, bacterial, fungal and plant species, as well as with soils. This developed PMP method allowed the separation and quantification of 18 sugar-related compounds, including four amino sugars, three N-acetyl amino sugars, eight neutral sugars, and three uronic acids within 20 min. This PMP method showed a precision for isotope enrichment detection of 0.03–0.05 atom % 13C for D-glucose and D-glucosamine. This is the first time talosaminuronic acid (deriving from archaeal pseudopeptidoglycan) was identified and quantified using PMP derivatization. The application of this novel PMP method on pure hydrolyzed biomass and soils, showed the successful chromatographic and mass spectrometric separation and quantification of amino sugar, neutral sugar and uronic acid compounds. A multivariate analysis using these sugar-related PMP derivatives showed a clustering of the species according to their respective taxonomic group (archaea, gram-positive bacteria, gram-negative bacteria, fungi and plants). The modified PMP method can be applied to identify and quantify soil microbial necromass biomarkers, as well as their contribution to SOM. The sensitive isotope tracer detection allows tracing isotopically labeled materials into necromass biomarkers in SOM pools. • 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization for necromass biomarkers via LC-Orbitrap MS. • Common bacterial and fungal necromass biomarkers extended to plants and archaea. • Talosaminuronic acid indicative for archaea, hexoses for plants. • Sensitive to trace isotopically labeled substrates into necromass. • Facile application to complex environmental samples (soils). [ABSTRACT FROM AUTHOR]

Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated. The gum was extracted by maceration of the inner bark in deionised water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated. The GG extract had total carbohydrate content of ∼60% out of which 11.8% was starch, and a protein content of 2.3%. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH. [ABSTRACT FROM AUTHOR]

The importance of common beans ( Phaseolus vulgaris ) in addressing food insecurity cannot be underestimated. However, their utilization is hampered by development of the hard-to-cook (HTC) defect, i.e., the inability of cotyledons to soften sufficiently within a reasonable time during cooking, the presence of flatulence causing oligosaccharides, the antinutrients and the low digestibility of macronutrients. The objective of this study was to determine the effect of storage conditions (time, temperature and relative humidity) on pectic polysaccharides of selected common bean varieties during the evolution of the hard cook problem. First, alcohol insoluble residue (AIR) was extracted from the bean flour. The AIR was fractionated into water, chelator and Na 2 CO 3 -soluble pectin fractions and a hemicellulose fraction. The galacturonic acid content, neutral sugars, degree of methylesterfication (DM), degree of acetylation (DAc) and molar mass distribution for pectin fractions were determined. In addition, filterable residual protein in various fractions was estimated. Results on the acidic and neutral sugars revealed that common beans contained highly branched, arabinose-rich pectic polysaccharides. Storage of common beans for more than 4 months at high relative humidity (83%) and high temperature (45 °C) resulting in HTC development showed a decrease in pectin extractability in water paralleled by an increase in the alkaline-soluble fraction. Other pectin characteristics such as DM and DAc showed minor variations upon storage of beans. The hydrolysis of both starch and proteins before AIR extraction decreased with increasing storage time, temperature and relative humidity. The increase in residual starch and protein might be linked to the protein–starch hypothesis where predominance of protein denaturation leads to restricted starch gelatinization. The results reveal that the contribution of pectic polysaccharides to development of HTC defect during the storage of Canadian wonder and Red haricot common beans at elevated temperature and relative humidity is due to reduced pectin solubility. However, the influence of starch and proteins seems evident. [ABSTRACT FROM AUTHOR]

There is a growing recognition that unless soil hydrophilic fulvic acid (HiFA) is studied together with soil hydrophobic FA (HoFA), we will not fully understand the characteristics of the FA fraction in soils. The aim of this study was to characterize soil HiFA, which were extracted from soil and purified by tangential flow ultrafiltration (TFU), by means of elemental (C, H, O, N, S) and isotope (13C, 15N) analyses, Fourier transform IR (FT-IR) and fluorescence spectroscopy and neutral sugars analysis. Results revealed marked differences between HiFA and HoFA in terms of chemical (elemental, isotopic and neutral sugar compositions) and spectroscopic properties (FT-IR, fluorescence spectra). The HiFA carbon accounted for 46 to 80% of the total FA carbon and thus, an important constituent of the FA fraction. On average, neutral sugars contents in HiFA is twofold larger than in HoFA and are mostly dominated by rhamnose, galactose, and fucose, while in HoFA, mannose was the most abundant neutral sugars, indicating that not only quantity, but also quality of neutral sugars varies between HiFA and HoFA. To further enhance the understanding of the characteristics and composition of soil HiFA including its turnover rate, fate and chemical transformation in soils, it is indispensable to isolate and purify HiFA. As such, purification of soil HiFA by TFU is satisfactory for such purpose. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the efficiency of delinting time of cottonseeds through the electrical conductivity and the quantity of neutral sugars and uronic acids leaked from the seeds during imbibition in water, in function of the fractioning in water and the artificial ageing. The seeds were delinted with commercial sulphuric acid for 1.5 and 4.5 minutes, separeted according to the sedimentation fractions in water and submitted to artificial ageing for 0, 72 and 96 hours. Electrical conductivity, contents of neutral sugars and uronic acids were determinated from the exudate resulting from the seeds imbibition in relation different treatments. The results showed that the delinting time for 1.5 minutes provided higher values of electrical conductivity, higher contents of neutral sugars and lower contents of uronic acids in relation with delinted seeds.

BACKGROUND: Blueberry cultivars with very firm, crisp fruit textures have been developed to increase consumer acceptance and as an aid in production and marketing. The basis for the crisp fruit texture is unknown. OBJECTIVES: The objective of this study was to compare the bioyield force (BF) and cell wall composition of crisp and standard texture blueberry genotypes. METHODS: Bioyield force of seven southern highbush blueberry genotypes having standard ('Springhigh', 'Star', Windsor') and crisp ('Sweetcrisp', FL06-561, FL06-562, and FL98-325) fruit texture was measured on fresh, whole fruits. Dry weight, alcohol insoluble residue (AIR), uronic acids (UA), and neutral sugars (NS) were then measured on separated flesh and skin tissue. RESULTS: The BF of the standard texture genotypes was significantly less than all four crisp genotypes. There were differences in the dry weight and AIR among genotypes, but these differences did not correspond to crisp and standard texture classes. There was no significant difference among genotypes in the measurement of UA or NS. CONCLUSIONS: These results confirm that there is a phenotypic difference between crisp and standard texture blueberry genotypes that can be detected with BF measurements, but that quantitative differences among total cell wall material, pectins, and neutral sugars were not responsible for the variability of these texture types. [ABSTRACT FROM AUTHOR]

The occurrence of the hard-to-cook (HTC) defect in legumes is characterized by the inability of cotyledons to soften during the cooking process. This phenomenon may be influenced by pectin properties. The objective of this study was to characterize the pectic polysaccharides comprised in the alcohol insoluble residue (AIR) extracted from easy-to-cook (Rose coco) and hard-to-cook (Pinto) common beans. This would provide an insight in the relationship between the pectin properties and HTC defect. The AIR was extracted from raw, half-cooked hard, half-cooked soft and fully-cooked bean samples. Subsequently, it was fractionated into water-, chelator- and Na 2 CO 3 -soluble pectin fractions and a hemicellulose fraction. For the AIR and the pectin fractions, determination of the galacturonic acid content, neutral sugars, degree of methylesterfication (DM), degree of acetylation (DAc) and molar mass (MM) distribution was performed. Results on the pectin fractions, MM distribution and pectin content profile, revealed that Rose coco pectin generally showed higher pectin solubility than Pinto. Neutral sugar profiles indicated that Pinto contained higher amounts of branched pectin (i.e. arabinans) than Rose coco. There was no difference between the DM of Pinto and Rose coco, however, the DAc was higher in Rose coco. In conclusion, the differences in pectin structure and solubility properties between easy- and hard-to-cook common beans might contribute to the differences in their cooking behavior. [ABSTRACT FROM AUTHOR]

Abstract: While the fruit pulp of purple pitaya (Hylocereus sp.) is highly valued, its pericarp is unsuitable for consumption. Cell wall polysaccharides of fruit pericarp were analyzed to identify potential valorization of this by-product. The alcohol insoluble residue (AIR) was extracted yielding 6.16±0.09% on FW of AIR, which was subsequently fractionated into water-, oxalate-, acid- and alkali-soluble pectins, hemicellulose and cellulose. Water and oxalate-soluble pectin were the major pectin fractions. Anhydrouronic acid (AUA) contents of the AIR and of the fractions were measured using the m-hydroxydiphenyl (MHDP) assay, resulting in 24.1% of the AIR. AUA contents were higher in the water (WSP) and oxalate (OXP) soluble pectin fractions, reaching 46.62 and 56.16% of their total, respectively. Moreover, the degree of esterification (DE) of the AIR and its fractions was determined spectrophotometrically, where the highest DE values were found in the WSP and acid (HSP) soluble fractions. Fractions were analyzed for their neutral sugar composition by gas chromatography after derivatization. Pectin fractions were mainly composed of arabinose, galactose and rhamnose, while the hemicellulose fraction mainly consisted of glucose and xylose. The thickening properties of the AIR were evaluated after determining relative viscosities of AIR solutions and comparing the data with various mathematical models. With increasing shear rates a power law decay of shear viscosity was observed for AIR solutions indicating structure viscous shear-thinning behavior. Flow curves of 1% solutions of commercial thickeners showed high similarity to a 5% solution of pitaya AIR, thus indicating the requirement of further purification of the pitaya AIR. [Copyright &y& Elsevier]

Background: The endophytic fungus, Neotyphodium coenophialum, can enhance drought tolerance of its host grass, tall fescue. To investigate endophyte effects on plant responses to acute water deficit stress, we did comprehensive profiling of plant metabolite levels in both shoot and root tissues of genetically identical clone pairs of tall fescue with endophyte (E+) and without endophyte (E-) in response to direct water deficit stress. The E- clones were generated by treating E+ plants with fungicide and selectively propagating single tillers. In time course studies on the E+ and E- clones, water was withheld from 0 to 5 days, during which levels of free sugars, sugar alcohols, and amino acids were determined, as were levels of some major fungal metabolites. Results: After 2-3 days of withholding water, survival and tillering of re-watered plants was significantly greater for E+ than E- clones. Within two to three days of withholding water, significant endophyte effects on metabolites manifested as higher levels of free glucose, fructose, trehalose, sugar alcohols, proline and glutamic acid in shoots and roots. The fungal metabolites, mannitol and loline alkaloids, also significantly increased with water deficit. Conclusions: Our results suggest that symbiotic N. coenophialum aids in survival and recovery of tall fescue plants from water deficit, and acts in part by inducing rapid accumulation of these compatible solutes soon after imposition of stress. [ABSTRACT FROM AUTHOR]

A reversed-phase high-performance liquid chromatographic method with fluorometric detection is proposed for the simultaneous determination of different classes of neutral sugars, such as hexoses (galactose, glucose and mannose), pentoses (arabinose and xylose), deoxy-hexoses (fucose and rhamnose), as well as acidic sugars (galacturonic and glucuronic acids). The separation is carried out on a hydrophilic end capped C column following a pre-column derivatization with p-aminobenzoic acid. The fluorometric detection of the derivatives has shown a strong dependency with the mobile phase pH. The performance of the proposed methodology was evaluated and the prerequisites of linearity ( r-value > 0.999), precision (intra-day CV < 6 % and inter-day CV < 11 %) and recovery (between 77 ± 7 and 103 ± 3 %) were satisfied. To our knowledge, the obtained values of limit of detection for neutral sugars (within the range 6.1-28 μg L) are the lowest reported using this derivatizing agent. In order to better judge the methodology presented herein, neutral sugars of a pectin-rich orange extract were also analysed by the conventionally used GC-FID (gas-chromatography with flame ionization detector) method of alditol acetate derivatives. A statistical test (paired t test) has proved that no significant differences (α = 0.05) were observed between these two methods. [ABSTRACT FROM AUTHOR]

Abstract: A method is described to simultaneously determine the neutral, amino, and acidic sugar content of combined carbohydrates in high molecular weight (HMW, >1kDa) dissolved organic matter and in particles from seawater samples. Monomeric sugars are determined after acid hydrolysis and neutralization through acid evaporation using high performance anion exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD). The separation of sugars during chromatography is achieved in two steps, an isocratic elution (18mM NaOH) followed by a gradient course of two mobile eluent phases (NaOH and CH3COONa). HPAEC-PAD has previously been applied to measure neutral and amino sugars in marine samples. Since salt anions interfere with the measurement, some of the earlier studies used ion exchange resins for seawater desalting. Thereby, variable losses of neutral and amino sugars, and the complete removal of acidic sugars have been reported. Here, we show that desalting by membrane dialysis (1kDa) is an efficient alternative to ion exchange resins and yields recoveries of >90% for HMW carbohydrates. We conducted several tests to determine the accuracy and reproducibility of the method. Sugar concentrations determined with our protocol were compared to results obtained with the colorimetric TPTZ-method, and with earlier HPAEC-PAD protocols using cation/anion exchange resins. Applications of our protocol to field samples indicated that acidic sugars can comprise a substantial fraction (30–50%) of HMW dissolved carbohydrates in seawater. The simultaneous analysis of the three classes of sugars appears promising to detect a larger fraction of marine combined carbohydrates, and thus to improve our understanding of organic matter cycling in the ocean. [Copyright &y& Elsevier]

Abstract: In a long-term tillage experiment comparing mouldboard plough and rotary harrow since 1967, litterbags with green maize residues and wheat straw were buried, recovered from soil and analysed for biochemical degradation indices. Our objective was to investigate whether lignin units and neutral and amino sugars give information on microbial degradation after burial periods of 6 and 12months at two different depths (0–5 and 15–20cm). Tillage and burial depth had no effects on the content and composition of lignin. In contrast, the extended burial period resulted in higher acid/aldehyde ratios of vanillyl units, due to increasing microbial oxidation, and in higher ratios of cinnamyl/vanillyl units, due to the higher resistance of vanillyl units against microbial degradation. The contents of mannose, bacterial muramic acid, and fungal glucosamine were significantly higher in the plough than in the harrow treatment, due to a higher microbial colonisation. For the same reason, the extended burial period led to significant increases in the contents of mannose, glucosamine, muramic acid, and galactosamine as well as in the GM/AX ((galactose+mannose)/(arabinose+xylose)) ratio. The decline in the fungal C/bacterial C ratio indicated that bacterial colonisation of litter followed fungal colonisation with delay. A greater burial depth led to a lower microbial colonisation and consequently had contrasting effects to those of a longer burial period. Treatment effects on maize residues and wheat straw were generally similar, despite the strong differences in composition. The combination of litterbags and biochemical degradation indices gave further evidence that lower tillage intensity reduces microbial turnover and decomposition activity. [Copyright &y& Elsevier]

Abstract: The composition of cell wall polysaccharides of pitaya (Hylocereus sp.) fruit pulp was studied with the aim of designing proper maceration processes for the fruit processing industry. Therefore, the degree of esterification of pectin was determined through a potentiometric titration and the consistency with a Bostwick consistometer. Moreover, the alcohol insoluble residue (AIR) was extracted and subsequently fractionated into water-, oxalate-, acid- and alkali-soluble pectins, hemicellulose and cellulose. Each fraction was analyzed for its neutral sugar composition by gas chromatography. Additionally, the AIR uronic content was measured by the m-hydroxydiphenyl (MHDP) assay. Pectin fractions in the analyzed fruit pulp were composed mainly of arabinose and galactose, while the hemicellulose fraction consists mainly of glucose, xylose and galactose. Considering the limited uronic acid content (32.3%) in the AIR and the high esterification degree of pectin, the high viscous consistency of this fruit pulp might not be highly attributed to pectin fractions. [Copyright &y& Elsevier]

Abstract: Amino acids, neutral sugars and amino sugars were analyzed to investigate the chemical composition and diagenetic processing of suspended particulate organic matter (POM, >100 nm), high-molecular-weight dissolved organic matter (HMW DOM, 1–100 nm) and low-molecular-weight dissolved organic matter (LMW DOM, <1 nm) at the time-series stations near Bermuda (BATS) and Hawaii (HOT). Differences between BATS and HOT were principally related to location-specific biogeochemical processes and water mass ventilation ages. Concentrations of amino acids, neutral sugar and amino sugars in unfiltered seawater sharply declined with depth at both stations, indicating an upper ocean source and rapid turnover of these components. The size distribution of organic matter was heavily skewed to smaller molecular sizes. Depth comparisons showed that larger size classes of organic matter were more efficiently removed than smaller size classes. Carbon-normalized yields of amino acids, neutral sugars and amino sugars decreased rapidly with depth and molecular size. Together these biochemicals accounted for 55% of organic carbon in surface POM but only 2% of the organic carbon in LMW DOM in deep water. Chemical compositions showed distinct differences between organic matter size classes indicating the extent of diagenetic processing increased with decreasing molecular size. These findings are consistent with the size-reactivity continuum model for organic matter in which bioreactivity decreases with decreasing molecular size and diagenetic processes lead to the formation of smaller components that are resistant to biodegradation. The data also provided evidence for a size-composition continuum. Carbon-normalized yields of amino acids, neutral sugars and amino sugars were sensitive indicators of diagenetic alterations. Diagenetic indicators based on amino acid compositions revealed distinct patterns for the North Pacific and Sargasso Sea possibly indicating the influence of varying sources or diagenetic processing. [Copyright &y& Elsevier]

Four female Sika deer (mean bodyweight, 48 kg) and three male Holstein cattle (mean bodyweight, 209 kg) were offered alfalfa hay cubes at 2% (deer) and 2.5% (cattle) of bodyweight, respectively. The digestibility of the cell walls and cell wall components (rhamnose, arabinose, xylose, mannose, galactose and glucose) in alfalfa and its retention time of the alfalfa in the digestive tract and rumen parameters were determined. Cell walls and xylose were less digestible in the deer than in the cattle ( P < 0.01 and P < 0.05, respectively). The digestibility of galactose in the deer was as high as that in the cattle. The digestibility of the other sugars and total neutral sugars was numerically lower in the deer, but the differences were not significant. In the deer, mannose was most digestible, followed in order by galactose, arabinose, glucose, rhamnose and xylose; whereas, in the cattle, mannose was most digestible, followed in order by arabinose, glucose, galactose, rhamnose and xylose. The retention time in the digestive tract was shorter in the deer than in the cattle. In the deer, the number of ruminal protozoa was somewhat higher, and the concentrations of propionic acid and butyric acid were higher ( P < 0.05) than in the cattle. These results indicate that Sika deer might utilize pectic polysaccharides as a carbon source in preference to glucose containing polysaccharides such as cellulose. The lower digestibility of all cell wall components except galactose in the Sika deer might be mainly due to its shorter retention time. [ABSTRACT FROM AUTHOR]

Abstract: In vivo pectin solubility was examined in ripening and chill-injured tomato fruit with down-regulated polygalacturonase (PG, EC 3.2.1.15) activity and untransformed wild-type fruit by analyzing a pressure-extracted fluid of apoplastic origin. Pectin concentration in the apoplastic fluid increased threefold during ripening and was not affected by endogenous PG. In contrast, PG strongly affected pectin concentration in a bulk pericarp fluid obtained after tissue disruption. There was a 14-fold increase in bulk pectin levels during ripening of PG-antisense fruit and a 36-fold increase in wild-type. Pectins soluble in the apoplastic fluid decreased slightly during storage of fruit at 5°C for 14 days but increased considerably upon subsequent transfer to 15°C. Concentration of monomeric galactose in the apoplastic fluid increased during ripening from 41 to 67μgmL−1. Galactose levels were threefold to fourfold higher in the bulk than in the apoplastic fluid. Low-temperature storage caused a 50% reduction in the galactose present in the bulk fluid and a 20% reduction in apoplastic concentration of galactose. These results indicate that pectin dissolution in ripening tomato fruit is PG-independent even though the enzyme is catalytically active in ripe fruit. Low-temperature storage reduces in vivo pectin solubility, an effect that is reversed upon transfer to higher temperature following cold storage. [Copyright &y& Elsevier]

Abstract: Pectins are widely used in the food industry as gelling agents, and are also recognised to promote human health as dietary fibre. Commercially available pectins are similar in composition, with high uronic acid contents. A pectin rich in hairy regions was extracted under alkaline conditions. This sample contained 56g neutral sugars but only 15g uronic acids/100g and had a very complex molecular structure, with highly branched arabinan side chains. It was subjected to in vitro fermentation with fresh human faecal bacteria and compared to a commercial pectin and a larch arabinogalactan. The two pectins were metabolised completely within 6h, whereas approximately 20% of the arabinogalactan remained un-degraded after 24h. Higher amounts of short-chain fatty acids were produced from the pectin hairy regions than from the commercial preparation with propionate being more than doubled. Concomitantly, the pH was lowered to a larger extent. These two features are of interest from a physiological point of view, since they are considered to be beneficial to colon health. Thus, pectin fractions rich in hairy regions might be an interesting dietary fibre with slightly improved physiological properties compared to commercial pectins. [Copyright &y& Elsevier]

Dissolved organic matter (DOM) was sampled by tangential flow ultrafiltration from different basins in the central Arctic Ocean, the Greenland, Iceland and Norwegian (GIN) Seas, and the estuaries of the Ob and Yenisei Rivers. Dissolved organic carbon (DOC) concentrations ranged from more than 500 μM C in the rivers to about 50 μM C in the deep basins. Arctic Mediterranean Sea (AMS) surface water DOC concentrations ranged from 66 to 137 μM C. High concentrations in surface waters were due mainly to river discharge of terrigenous DOC, while elevated concentrations in AMS deep water likely reflect downwelling of DOM in this system. Total hydrolyzable neutral sugar concentrations were ∼7-fold higher in ultrafiltered DOM (UDOM) from estuaries (1200 nM) than in Arctic ocean surface waters (160 nM), but carbon-normalized neutral sugar yields (% OC) were lower in the estuaries indicating that marine DOM sources were relatively rich in neutral sugars. Depth profiles of neutral sugar concentrations and carbon-normalized yields indicated that carbohydrates were produced and consumed largely in surface waters of the AMS. These observations were consistent with rapid bacterial degradation of neutral sugars during decomposition experiments. The molecular composition of neutral sugars was very similar among AMS surface samples and showed only minimal differences between terrestrial and marine UDOM, indicating that the neutral sugar composition is not useful for distinguishing these sources. It appears diagenetic processes rather than sources are primarily responsible for determining neutral sugar compositions in UDOM. Neutral sugar compositions in all of the UDOM samples analyzed in this study were indicative of heteropolysaccharides. The strong relationship between neutral sugars and the diagenetic state of DOM was best represented by neutral sugar yields (% OC), which were used as a quantitative indicator for the amount of labile DOM in the AMS. Based on the low average neutral sugar yield (5.5% OC) in UDOM from AMS surface waters, we estimated that only ∼2.2% of the DOC was of labile nature. This value was lower than for surface waters of the Ross Sea and Atlantic and Pacific Oceans suggesting DOM is less bioavailable and the microbial loop is less active in AMS surface waters. [Copyright &y& Elsevier]

We assessed the contribution of polysaccharides and lignin, major components of plant residues, to the refractory pool of soil organic carbon (SOC) in arable soils. Soil samples from two contrasting treatment types of European long-term agroecosystem experiments, i.e. conventionally managed (fertilized) and C-depleted plots, enriched in refractory compounds, were compared. Bulk samples from eight experimental sites and particle-size fractions of two of the sites were investigated. The CuO oxidation technique was used as a relative measure of lignin and its degree of structural alteration. The contents and composition of polysaccharides were determined following hydrolysis with trifluoroacetic acid (TFA). For the bulk samples, the amount of lignin phenols declined more than the total OC in the course of C-depletion. The contribution of lignin phenols to total OC was thus lower in the C-depleted versus the fertilized plots. A greater lignin biodegradation was found in the bulk samples of the depleted plots compared with the fertilized plots. The analysis of size fractions revealed lower OC-normalized contents of lignin phenols and a higher degree of lignin alteration in fractions <63 μm of the depleted versus the fertilized plots. These findings indicate that lignin does not accumulate within the refractory C pool of arable soils. The refractory SOC pool shows a lower contribution of lignin as compared with more labile fractions of SOC. If lignin-derived carbon is present in the stable pool it has been extensively modified so that it can no longer be identified as phenolic CuO oxidation products. OC-normalized contents of polysaccharides (neutral sugars and galacturonic acid) were similar in bulk samples of the C-depleted and fertilized plots. The contrasting treatments showed similar polysaccharide contents especially in separates <6 μm. The separates <6 μm in the C-depleted plots retained between 50 and 100% of the polysaccharide amounts in the fertilized plots. The mass ratio of (galactose+mannose)-to-(arabinose+xylose) (GM/AX) was higher in bulk samples of the C-depleted versus the fertilized plots, indicating a higher relative contribution of microbial sugars. Within a particular soil, the fine separates were those with the highest GM/AX ratio. These results indicate that the refractory C pool has a similar proportion of polysaccharides as the labile C pool, but refractory polysaccharides are mainly associated with fine separates and show a dominant contribution of microbial sugars. Our results provide evidence that polysaccharides, mainly those of microbial origin, are stabilized over the long-term within fine separates of arable soils. In contrast, CuO lignin is associated mainly with the coarse fractions and does not contribute to the refractory C pool. [Copyright &y& Elsevier]

• Long-term drainage induced divergent changes of SOC contents in fen and bog. • Both plant- and microbial-dominated soil fractions increased in drained fen. • Microbial sugars increased at the expense of plant sugars in drained bog. • Drainage enhanced soil "microbial carbon pump" both in fen and bog. Drainage-induced changes in wetland soil organic carbon (SOC) composition and origin are poorly investigated compared to SOC stocks. Here, using soil fractionation and neutral sugars, we find that long-term drainage increased both plant- and microbial-dominated (i.e., light and mineral-associated, respectively) fractions in a fen while microbial residues increased at the expense of plant residues in a drained bog, accompanied by divergent changes of SOC contents. These findings highlight stimulated soil "microbial carbon pump" in drained wetlands, whose efficiency deserves further investigation related to wetland SOC persistence. [ABSTRACT FROM AUTHOR]

Senescence of carnation (Dianthus caryophyllus L. cv. White Sim) petals coincided with a decrease on a per flower basis in the yield of cell wall and ethanol-insoluble solids. The decrease in cell wall yield per flower was due largely to a loss of neutral sugars, primarily galactose (45%) and arabinose (23%). On a per flower basis, water and chelator-soluble pectins increased throughout development, comprising in senescent petals 18 and 58%, respectively, of total pectin. Alkali-soluble pectins ranged from 35 to 45% of the total pectin and decreased during senescence. Gel chromatography of chelator- and alkali-soluble pectins revealed no change in molecular size and polygalacturonase activity was not detected. Large-molecular-size hemicelluloses decreased during development, and observation reminiscent of the changes affecting hemicelluloses during the ripening of a number of fruit types. Compositional analysis of the large hemicellulosic polymers revealed a decrease in xylose and galactose content. [ABSTRACT FROM AUTHOR]

The loss of flesh firmness during muskmelon (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit ripening was related temporally to modifications of pectic and hemicellulosic polysaccharides, and a net loss of non-cellulosic neutral sugars. An increase in solubility and a decrease in molecular size of polyuronides occurred during ripening; however, the decrease in molecular size was apparently not the result of polygalacturonase (EC 3.2.1.15) activity. Molecular size of hemicelluloses shifted from larger to smaller polymers during ripening, and this decrease was accompanied by changes in neutral sugar composition. Galactose, glucose, and xylose were the predominant neutral sugars in the hemicellulosic polymers. On a mol% basis there were decreases in galactose and glucose in large hemicellulosic polymers with ripening. Relative xylose content approximately doubted in the large polymers during ripening; xylose was the predominant neutral sugar in the small polymers and remained fairly constant. [ABSTRACT FROM AUTHOR]

Nine actinomycete melanins synthesized under various culture conditions, eight of them by actinomycete samples isolated from Brazilian topsoils under savanna (cerrado) vegetation and one from an ATCC sample, were subjected to a two-step hydrolysis procedure and the sugars released qualitatively and quantitatively determined by capillary gas-liquid chromatography (GLC). Humic acids (HAs) extracted from these soils, analysed previously, were used for comparison. The neutral sugars glucose, galactose, mannose, xylose, arabinose, ribose, rhamnose and fucose and the alcohol sugar inositol were present in varying amounts in most of the melanins analysed. The same sugars were present in the HAs used for comparison, except for ribose. Some qualitative and quantitative differences observed in the two types of macromolecules would be expected, considering their origins. The results indicate that the actinomycete melanins have a qualitative sugar distribution pattern similar to that of the HAs from Brazilian tropical soils and of HAs reported for soils from other climatic regions. The possible participation of actinomycete melanins in the formation of soil humic substances is discussed. [ABSTRACT FROM AUTHOR]