Xylose Content Research Articles

Isolation of C5-Sugars from the Hemicellulose-Rich Hydrolyzate of Distillers Dried Grains

A three-stage process for isolation and separation of C5-sugars in dry form from the hydrolyzate of distillers dried grains (DDG) is described. The salient features include extraction of bis(boronic ester) adducts of xylose and arabinose into toluene on treatment of neutralized hydrolyzate with phenylboronic acid (PBA) and subsequent addition of propylene glycol to the organic phase to induce sugar precipitation for ready collection. The PBA used in the process is largely reclaimed on hydrolysis of the propylene glycol boronic ester formed during the process. A preparative scale example afforded 48% of the xylose content in DDG as a crystalline solid also containing an additional 11% of the arabinose content.

Fermentative biohydrogen production using hemicellulose fractions: Analytical validation for C5 and C6-sugars, acids and inhibitors by HPLC

Hemicellulose fractions derived from lignocellulosic biomass acid pretreatments have been considered promising substrates for H2 production via anaerobic fermentation. In this context, the objective of this study is to develop a high-performance liquid chromatography (HPLC) methodology for the simultaneous determination of glucose, xylose, arabinose, acetic acid, butyric acid, 5-hydroxymethyl-2-furaldehyde (HMF) and 2-furaldehyde (furfural) in the complex matrices used for the H2 production from hemicellulose fractions. HPLC analyses were performed using two columns under different conditions: the Aminex HPX-87H column (mobile phase consisted of 0.005 mol L−1 H2SO4 solution at a flow rate of 0.7 mL min−1 and temperature of 60 °C) and the Rezex RFQ Fast acid (mobile phase consisted of 0.005 mol L−1 H2SO4 solution at a flow rate of 1.0 mL min−1 and temperature of 80 °C). Acids (acetic and butyric acids) and inhibitors (HMF and furfural) were analyzed by UV–Vis detection at 210 nm, and C6 and C5-sugars (glucose, xylose and arabinose) were analyzed using a refractive index detector (RI). Some validation parameters, such as selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy and robustness were successfully evaluated. The monitoring of fermentative media for H2 production from different hemicellulose fractions was successfully performed using the proposed methodologies. The acid-pretreated samples from corn cob, cocoa husk, sugarcane straw and bagasse substrates presented a range of xylose contents from 84.85 to 222.98 mmol L−1, which resulted in a maximum production of 2.99 mol H2/mol total carbohydrate.

발아 전후 보리 당단백질 추출물의 영양성분 및 면역 활성 변화

In the present study, we investigated changes in the nutritional components of pre- and post-germinated barley seeds and also investigated their immune-enhancing effects such as production of nitric oxide (NO), interleukin (IL)-6, and tumor necrosis factor (TNF)-α on the RAW 264.7 macrophage cell line. Protein and total sugar contents increased slightly with increase in germination time. The major neutral sugars of germinated balrey seeds were arabinose, glucose, and xylose. Glucose content decreased during germination, whereas arabinose and xylose contents increased during germination. Amino acid contents of barley germinated for 24 and 48 hours increased 1.03-fold and 1.24-fold, respectively, compared to that of pre-germinated barley. Moreover, RAW 264.7 macrophages stimulated with barley germinated for 24 and 48 hours showed higher production of NO, IL-6, and TNF-α compared to that observed in pre-germinated barley. The results of the present study indicate that germinated barley may have immune-enhancing effects derived from its ability to activate RAW 264.7 macrophages, which play a major role in innate immunity.

Functional relationship of furfural yields and the hemicellulose-derived sugars in the hydrolysates from corncob by microwave-assisted hydrothermal pretreatment.

BackgroundCorncob as one of the most suitable feedstock for the production of a variety of high-value-added chemicals is receiving increasing attention worldwide because of the characteristics of high carbohydrate (cellulose and hemicelluloses) contents and high energy densities. Furfural produced from hemicelluloses is a highly versatile and key feedstock used in the manufacture of a wide range of biofuel and important chemicals in different fields. Achieving high furfural yields from corncob combining green approaches and efficient equipment has the promising potential for biomass-to-biofuel technologies. To understand the dissolving mechanism of corncob sugars and reveal the relationship between the hydrolysate composition and furfural yields, a two-step approach was proposed using microwave-assisted hydrothermal pretreatment and subsequently heterogeneous catalytic process.ResultsReleased hemicelluloses in the first stage were mainly in forms of monosaccharide, oligosaccharides, and water-soluble polysaccharide. Hydrolysates with the maximum xylose content (99.94 mg g−1, 160 °C, 90 min), the maximum xylobiose content (20.89 mg g−1, 180 °C, 15 min), and the maximum total xylose content in monosaccharide and oligosaccharides (DP ≤ 6) (272.06 mg g−1, 160 °C, 60 min) were further converted to furfural using tin-loaded montmorillonite as the catalyst in a biphasic system. The highest furfural yield (57.80 %) was obtained at 190 °C for 10 min from hydrolysates with the maximum xylose content. Moreover, controlled experiments showed that furfural yields from corncob hydrolysates were higher than those from the pure xylose solutions, and lower initial xylose concentration may be in favor of the furfural production.ConclusionsThis work provides an efficient approach to produce furfural by a two-step process for the biomass-to-biofuel industry. Results indicated that the production of furfural from biomass raw materials can be controlled by the depolymerization degree of hemicelluloses.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0314-z) contains supplementary material, which is available to authorized users.

Structural and Thermal Investigation of Three Agricultural Biomasses Following Mild-NaOH Pretreatment to Increase Anaerobic Biodegradability

In this work mild-alkaline semi-solid state pretreatments (NaOH: 2; 4; 6 %, at 25 °C, TS 10 %) were applied to Arundo donax, Sorghum bicolour L. and wheat straw (Triticum aestivum, L.) to test their efficiency on anaerobic biodegradability. The simple sugars (glucose, xylose, arabinose) from structural carbohydrate and the lignin content were analyzed in raw treated samples. Besides to this their structural variation were assessed by means of FT-IR and thermal analysis. The recovery of glucose (1–2 %), xylose (0.4–2.5 %), and arabinose (0.1–8.7 %) in the alkaline eluate showed the treatment produced moderate hydrolysis of the structural components. This was confirmed by the moderate variation of glucose, xylose, arabinose and lignin content determined in the solid residue. On the contrary the FT-IR analysis showed the solid fraction of samples had intense variations in the cellulose and hemicellulose structure (mainly saponification of ester bounds), also confirmed by thermal analysis. The maximum degradation rate (−dx/dtmax; s−1) of cellulose and hemicellulose increased in both Arundo and Sorghum, indicating a structural cleavage. Straw showed moderately increased resilience of hemicellulose by small temperature shifts. A general decrease of the apparent activation energy (Ea) was found in all samples as an indication of decreased structural order favourable to enzymatic hydrolysis and the additional anaerobic biodegradability, as proved by the anaerobic tests in which A. donax showed the highest increase of biodegradability at NaOH 6 % (+30 %) > wheat straw (+22 %) > Sorghum (11 %).

New studies on basil (Ocimum bacilicum L.) seed gum: Part I – Fractionation, physicochemical and surface activity characterization

Basil seed gum (BSG) was fractionated by non-solvent fractionation method (ethanol precipitation). Two fractions were obtained and called PER-BSG and SUPER-BSG which had the highest and lowest molecular weight (MW), respectively. Another fraction was obtained by protease treatment which protein moieties of BSG removed without making different in molecular weight. The molecular weight, moisture, ash, protein content, intrinsic viscosity, total sugar, total uronic acid, monosaccharide units, functional groups (FTIR) and surface tension were investigated for total BSG and all fractions. BSG was composed of 92.44% (w/w) sugar and 6.51% (w/w) uronic acid; while PER-BSG and SUPER-BSG comprised of 83.02% and 88.39% (w/w) sugar, and 3.84% and 13.39% uronic acid, respectively. FTIR results confirmed the presence of uronic acid as it had absorptions at wavenumber 1400 and 1600 cm−1. Significant difference was determined between monosaccharide compositions of fractions; especially in xylose content which substantial value existed for SUPER-BSG (10%). The BSG exhibited higher intrinsic viscosity (39.27 dl g−1) in comparison to its fractions. BSG and all fractions had the same molecular conformation which random coil conformation was recognized in dilute regimes and SUPER-BSG had the highest chain flexibility. The SUPER-BSG imparted the best surface activity as it had the highest protein content and lowest MW. Decreasing protein content by enzyme hydrolysis led to surface activity of BSG reduced considerably by changing its hydrophobic character. This attribute confirmed that protein and molecular weight plays an important role in surface activity of BSG.

Active fungal GH115 α-glucuronidase produced in Arabidopsis thaliana affects only the UX1-reactive glucuronate decorations on native glucuronoxylans

BackgroundExpressing microbial polysaccharide-modifying enzymes in plants is an attractive approach to custom tailor plant lignocellulose and to study the importance of wall structures to plant development. Expression of α-glucuronidases in plants to modify the structures of glucuronoxylans has not been yet attempted. Glycoside hydrolase (GH) family 115 α-glucuronidases cleave the internal α-D-(4-O-methyl)glucopyranosyluronic acid ((Me)GlcA) from xylans or xylooligosaccharides. In this work, a GH115 α-glucuronidase from Schizophyllum commune, ScAGU115, was expressed in Arabidopsis thaliana and targeted to apoplast. The transgene effects on native xylans’ structures, plant development, and lignocellulose saccharification were evaluated and compared to those of knocked out glucuronyltransferases AtGUX1 and AtGUX2.ResultsThe ScAGU115 extracted from cell walls of Arabidopsis was active on the internally substituted aldopentaouronic acid (XUXX). The transgenic plants did not show any change in growth or in lignocellulose saccharification. The cell wall (Me)GlcA and other non-cellulosic sugars, as well as the lignin content, remained unchanged. In contrast, the gux1gux2 double mutant showed a 70% decrease in (Me)GlcA to xylose molar ratio, and, interestingly, a 60% increase in the xylose content. Whereas ScAGU115-expressing plants exhibited a decreased signal in native secondary walls from the monoclonal antibody UX1 that recognizes (Me)GlcA on non-acetylated xylan, the signal was not affected after wall deacetylation. In contrast, gux1gux2 mutant was lacking UX1 signals in both native and deacetylated cell walls. This indicates that acetyl substitution on the xylopyranosyl residue carrying (Me)GlcA or on the neighboring xylopyranosyl residues may restrict post-synthetic modification of xylans by ScAGU115 in planta.ConclusionsActive GH115 α-glucuronidase has been produced for the first time in plants. The cell wall–targeted ScAGU115 was shown to affect those glucuronate substitutions of xylan, which are accessible to UX1 antibody and constitute a small fraction in Arabidopsis, whereas majority of (Me)GlcA substitutions were resistant, most likely due to the shielding by acetyl groups. Plants expressing ScAGU115 did not show any defects under laboratory conditions indicating that the UX1 epitope of xylan is not essential under these conditions. Moreover the removal of the UX1 xylan epitope does not affect lignocellulose saccharification.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-015-0154-8) contains supplementary material, which is available to authorized users.

Effects of Post-harvest Storage Duration and Variety on Nutrient Digestibility and Energy Content Wheat in Finishing Pigs.

This study was conducted to investigate the effects of post-harvest storage duration and wheat variety on the digestibility and energy content of new season wheat fed to finishing pigs. Two wheat varieties (Shi and Zhong) were harvested in 2013 and stored in the warehouse of the Fengning Pig Experimental Base at China Agricultural University for 3, 6, 9, or 12 mo. For each storage period, 12 barrows were placed in metabolism crates and allotted to diets containing 1 of the 2 wheat varieties in a randomized complete block design. The experimental diets contained 97.34% wheat and 2.66% of a vitamin and trace mineral premix. With an extension of storage duration from 3 mo to 12 mo, the gross energy (GE) and crude protein (CP) of the wheat decreased by 2.0% and 12.01%, respectively, while the concentration of neutral detergent fiber (NDF), acid detergent fiber (ADF) and starch content increased by 30.26%, 19.08%, and 2.46%, respectively. Total non-starch polysaccharide, total arabinose, total xylose and total mannose contents decreased by 46.27%, 45.80%, 41.71%, and 75.66%, respectively. However, there were no significant differences in the chemical composition between the two wheat varieties with the exception of ADF which was approximately 13.37% lower in Shi. With an extension of storage duration from 3 mo to 12 mo, the digestible energy (DE), metabolizable energy (ME) content and the apparent total tract digestibility of GE, CP, dry matter, organic matter, ether extract, ADF and metabolizability of energy in wheat decreased linearly (p<0.01) by 5.74%, 7.60%, 3.75%, 3.88%, 3.50%, 2.47%, 26.22%, 27.62%, and 3.94%, respectively. But the digestibility of NDF changed quadratically (p<0.01). There was an interaction between wheat variety and storage time for CP digestibility (p<0.05), such that the CP digestibility of variety Zhong was stable during 9 mo of storage, while the CP digestibility of variety Shi decreased (p<0.05). In conclusion, the GE, DE, and ME of wheat was stable during the first 3 to 6 mo of post-harvest storage, and decreased during the following 6 to 12 mo of storage under the conditions of this study.

A novel steam explosion sterilization improving solid-state fermentation performance

Traditional sterilization of solid medium (SM) requires lengthy time, degrades nutrients, and even sterilizes inadequately compared with that of liquid medium due to its low thermal conductivity. A novel sterilization strategy, high-temperature and short-time steam explosion (SE), was exploited for SM sterilization in this study. Results showed that SE conditions for complete sterilization were 172°C for 2min and 128°C for 5min. Glucose and xylose contents in medium after SE sterilization increased by 157% and 93% respectively compared with those after conventional sterilization (121°C, 20min) while fermentation inhibitors were not detected. FTIR spectra revealed that the mild SE conditions helped to release monosaccharides from the polysaccharides. Bacillus subtilis fermentation productivity on medium after SE sterilization was 3.83 times of that after conventional sterilization. Therefore, SE shortened sterilization time and improved SM nutrition, which facilitated fermentability of SM and should promote economy of solid-state fermentation.

High-Throughput Method for Determining the Sugar Content in Biomass with Pyrolysis Molecular Beam Mass Spectrometry

There is an important need to assess biomass recalcitrance in large populations of both natural and transgenic plants to identify promising candidates for lignocellulosic biofuel production. In order to properly test and optimize parameters for biofuel production, the starting sugar content must be known to calculate percent sugar yield and conversion efficiencies. Pyrolysis molecular beam mass spectrometry (py-MBMS) has been used as a high-throughput method for determination of lignin content and structure, and this report demonstrates its applicability for determining glucose, xylose, arabinose, galactose, and mannose content in biomass. Biomass from conifers, hardwoods, and herbaceous species were used to create a 44 sample partial least squares (PLS) regression models of py-MBMS spectra-based sugar estimates on high-performance liquid chromatography (HPLC) sugar content data. The total sugar py-MBMS regression model had a R 2 of 0.91 with a 0.17 mg/mg root mean square error of validation indicating accurate estimation of total sugar content for a range of biomass types. Models were validated using eight independent biomass samples from multiple species, with predictions falling within errors of the HPLC data. With a data collection time of 1.5 min per sample, py-MBMS serves as a rapid high-throughput method for quantifying sugar content in biomass.

Endo-β-1,4-glucanases impact plant cell wall development by influencing cellulose crystallization.

Cell walls are vital to the normal growth and development of plants as they protect the protoplast and provide rigidity to the stem. Here, two poplar and Arabidopsis orthologous endoglucanases, which have been proposed to play a role in secondary cell wall development, were examined. The class B endoglucanases, PtGH9B5 and AtGH9B5, are secreted enzymes that have a predicted glycosylphosphatidylinositol anchor, while the class C endoglucanases, PtGH9C2 and AtGH9C2, are also predicted to be secreted but instead contain a carbohydrate-binding module. The poplar endoglucanases were expressed in Arabidopsis using both a 35S promoter and the Arabidopsis secondary cell wall-specific CesA8 promoter. Additionally, Arabidopsis t-DNA insertion lines and an RNAi construct was created to downregulate AtGH9C2 in Arabidopsis. All of the plant lines were examined for changes in cell morphology and patterning, growth and development, cell wall crystallinity, microfibril angle, and proportion of cell wall carbohydrates. Misregulation of PtGH9B5/AtGH9B5 resulted in changes in xylose content, while misregulation of PtGH9C2/AtGH9C2 resulted in changes in crystallinity, which was inversely correlated with changes in plant height and rosette diameter. Together, these results suggest that these endoglucanases affect secondary cell wall development by contributing to the cell wall crystallization process.

Comparison of SHF and SSF Processes Using Enzyme and Dry Yeast for Optimization of Bioethanol Production from Empty Fruit Bunch

Abstract Empty fruit bunch was considered as substrate for second generation of bioethanol because it consists of lignin, cellulose, and hemicelluloses. For lignocelluloses materials, it usually needs pretreatment and hydrolysis to convert cellulose into glucose. Two methods of enzymatic hydrolysis, Separated Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) were carried out in this study. The performance of both SHF and SSF was concerned to evaluate the effect of hydrolysis methods and enzyme concentration for producing ethanol. Pretreatment was conducted in a reactor using 10% sodium hydroxide at temperature 150 °C during 30 minutes. Two kinds of enzyme, Cellic® CTec2 and Cellic® HTec2 from novozyme were added in 15% (gr/ml) of pretreated EFB at pH 4.8. Four concentration of enzyme Cellic® CTec2, 10, 20, 30, 40 FPU per gram biomass were performed in SHF and SSF processes respectively, while Cellic® HTec2 was added 20% from Cellic® CTec2. Contents of glucose, xylose, and ethanol were recorded every 24 hours. Using 40 FPU of concentration enzyme, it could be produce 4.74% of ethanol in 72 hours fermentation by SHF process and 6.05% of ethanol in 24 hours by SSF process. From this study, the SSF method was considered as a better process than SHF due to rapidly ethanol production and the highest concentration of produced ethanol.

Multivariate analysis of coconut residues by near infrared spectroscopy

Near infrared (NIR) spectroscopy was used to determine the content of Klason lignin, acid-soluble lignin, total lignin, extractives, ash, acid-insoluble residue, glucose, xylose, rhamnose, galactose, arabinose, mannose and total sugars in coconut residues. The samples were analyzed at several processing stages: wet unground (WU), dried unground (DU) and dried and sieved (DS). Partial least squares models were built, and the models for the analytes exhibited R2>0.80, with the exceptions of rhamnose, arabinose, galactose, mannose and ash from all fractions, and the lignin content from the WU fraction, which were predicted poorly (R2<0.70). There were some significant differences between the models for the main lignocellulosic components at the various stages of biomass. These results proved that NIR spectroscopy is useful for analysis at biorefineries, and it can be used as a faster and more economical alternative to the standard methods.

Direct transformation of xylan-type hemicelluloses to furfural via SnCl4 catalysts in aqueous and biphasic systems

Direct catalytic transformation of xylan-type hemicelluloses to furfural in the aqueous system and the biphasic system were comparatively investigated under mild conditions. Screening of several promising chlorides for conversion of beech xylan in the aqueous system revealed the Lewis acid SnCl4 was the most effective catalyst. Comparing to the single aqueous system, the bio-based 2-methyltetrahydrofuran (2-MTHF)/H2O biphasic system was more conducive to the synthesis of furfural, in which the highest furfural yield of 78.1% was achieved by using SnCl4 as catalysts under the optimized reaction conditions (150°C, 120min). Additionally, the influences of xylan-type hemicelluloses with different chemical and structural features from beech, corncob and bagasse on the furfural production were studied. It was found that furfural yield to some extent was determined by the xylose content in hemicelluloses and also had relationships with the molecular weight of hemicelluloses and the degree of crystallization.

Kinetic Analysis of Xylose Production from Palm Pressed Fiber by Sulfuric Acid

Palm pressed fiber (PPF) is lignocellulosic materials containing xylose and glucose. These high sugars contained in PPF can be used as a substrate for ethanol production by microorganisms. The PPF was delignified using sodium hypochlorite as a pretreatment for sugars production. By using mathematic model, 30.6 g L -1 of xylose and 2.2 g L -1 of glucose was obtained under t he optimum condition of 5 % (v.v -1 ) H 2 SO 4 at 120 oC for 30 min. At this condition, acetic acid and furfural concentrations were produced at 7.2 g L -1 and 0.9 g L -1 , respectively. Kinetic parameters were also investigated in order to predict concentrations of xylose, glucose, acetic acid and furfural in the delignified PPF hydrolysate. Yield of xylose was 85.74% of the initial xylose content.

Antioxidant Capacity of Water‐Extractable Arabinoxylan from Commercial Barley, Wheat, and Wheat Fractions

ABSTRACTThe objective of this research was to analyze the antioxidant capacity directly of water‐extractable nonstarch polysaccharides (NSP) and feruloylated arabinoxylans (WEAX) following their characterization. NSP were isolated from barley, wheat, and wheat fractions (germ, bran, and aleurone). WEAX were extracted only from wheat fractions. Antioxidant capacity of NSP measured with the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS), and oxygen radical absorbance capacity (ORAC) assays was 24.0–99.0, 40.0–122.0, and 140.0–286.0μM Trolox equivalents (TE)/g, respectively. The antioxidant capacity of WEAX was 75.7–84.0, 58.0–105.0, and 110.0–235.0μM TE/g for those three assays. DPPH and ABTS were highly correlated to xylose content (R2 = 0.85), degree of substitution (R2 = −0.99), total phenolic acids (R2 = &gt;0.73), total phenolic content (TPC) (R2 = &gt;0.78), and ferulic acid content (R2 = &gt;0.86). ORAC was only influenced by TPC (R2 = 0.63). By taking yield and antioxidant capacity into account, NSP would provide about 0.4–4.2, 0.6–5.1, and 2.8–12.0μM TE/g of flour of radical scavenging activity as measured by DPPH, ABTS, and ORAC, respectively, compared with WEAX (0.4–1.0, 0.3–1.3, and 0.6–2.8μM TE/g). Our results suggest that NSP or WEAX may play a role in protection against free radicals in a food matrix and likely in the gastrointestinal tract.

Effect of Carbon Source on Properties and Antioxidant Potential of Exopolysaccharides Produced by Trametes robiniophila (Higher Basidiomycetes).

The effects of carbon source on properties and antioxidant potential of exopolysaccharides (EPS) produced by Trametes robiniophila were investigated in this study. The results indicated that the EPS production varied with five different carbon sources. The predominant carbohydrate compositions in EPSs identified were glucose and mannose. Then, FT-IR spectral analysis revealed prominent characteristic groups in the EPSs. Furthermore, thermogravimetric analysis (TGA) indicated the EPS with lactose as the carbon source showed different degradation behavior as compared to the other four EPSs, probably due to larger ribose content as one of major monosaccharides in the EPS. The variation also affects the antioxidant activities investigated by using hydroxyl and DPPH radical scavenging assay. Sucrose was the best carbon source from the viewpoint of antioxidant activity due to the relatively high xylose content in the EPS.

ANATOMY AND CHEMICAL COMPOSITION OF LIRIODENDRON TULIPIFERA STEMS INCLINED AT DIFFERENT ANGLES

The anatomical and chemical characteristics of reaction wood (RW) were investigated in Liriodendron tulipifera Linn. Stems of seedlings were artificially inclined at angles of 30 (RW-30), 50 (RW-50) and 70° (RW-70) from the vertical, and compared with normal wood (NW) from a vertical seedling stem. The smallest values for the wood fibre length and vessel number were observed in RW-50. The pit aperture angle was less than 10° in RW-30 and RW-50, in which reduced lignin content was observed in the S2 layer of the wood fibres. An increase in the glucose content and a decrease in the lignin and xylose content was observed in RW-50. The stem inclination angle affected the degree of RW development with regard to anatomical and chemical characteristics: the severest RW was observed in RW-50, followed by RW-30. RW-70 was similar in anatomical and chemical characteristics to NW, apparently because the inclination was too strong to enable recovery of its original position. In this case a vertical sprouting stem was formed to replace the inclined stem.

Production of prebiotic xylooligosaccharides from alkaline extracted wheat straw using the K80R-variant of a thermostable alkali-tolerant xylanase

Agricultural by-products are raw materials of importance for increased utilization of renewable biomass. Wheat straw is a raw material of significant production volume and is in this work used for production of xylooligosaccharides (XOS). Extraction of xylan by dilute alkali was followed by hydrolysis using a variant of the alkali-tolerant Bacillus halodurans S7 endoxylanase A mutated at K80R. The xylan yield was on average 56.5g xylose equivalents per kg dried, ground wheat straw, with 1 arabinose per 12 xylose residues. The K80R variant, which displayed higher specific activity than the wild type enzyme, was added at a load of 96U/g extracted xylan. The XOS-yield (xylobiose–xylopentaose) was evaluated at time intervals in the temperature range of 50–65°C, at pHs from 7 to 10. The enzyme was optimally active at 60°C up to pH 9. Hydrolysis was completed within 7h, resulting in 36% conversion of the xylan to predominantly xylobiose. Xylose content was low (2.4%) despite extended incubation, which is desirable for XOS-production. The XOS-containing hydrolysate was confirmed as a suitable carbon source for the putative probiotic strain Lactobacillus brevis DSM 1269, showing the applicability of the method to obtain prebiotic XOS.

Elevated O3 and wheat cultivars influence the relative contribution of plant and microbe-derived carbohydrates to soil organic matter

Soil carbohydrates are sensitive to changes in soil C inputs because of their fast turnover rates. However, the effects of elevated O3 on the content and composition of soil carbohydrates are rarely reported in agroecosystem. The objectives of this study were to investigate the effects of elevated O3 on the content and composition of soil neutral sugars in the two wheat cultivars with different O3-tolerance. Our results showed that elevated O3 decreased the total soil neutral sugars. At the wheat ripening stage, elevated O3 increased the contents of galactose (Gal), arabinose (Ara) and mannose (Man) in the O3-tolerant wheat and decreased the contents of xylose (Xyl), Gal and Ara in the O3-sensitive wheat. Significant interactive effects between elevated O3 and wheat cultivar were found in the ratios of (Man+Gal)/(Ara+Xyl) and Man/(Ara+Xyl). These two ratios increased with elevated O3 at the wheat ripening stage in both wheat cultivars, with higher ratios observed in the O3-sensitive wheat relative to the O3-tolerant wheat. Our results indicated that elevated O3 decreased the total neutral sugars and altered the relative contribution of plant- and microbe-derived carbohydrates to soil organic matter. Microbe-derived carbohydrates were dominant contribution to the total carbohydrates in the O3-sensitive wheat. These changes in the accumulation and origins of soil carbohydrates will influence the accumulation and decomposition of soil organic matter and ecosystem functioning in agroecosystem.