Higher Glucan Content Research Articles

The Mushroom Glucans: Molecules of High Biological and Medicinal Importance.

Carbohydrates, including polysaccharide macromolecules, are the main constituents of the fungal cell wall. Among these, the homo- or heteropolymeric glucan molecules are decisive, as they not only protect fungal cells but also have broad, positive biological effects on the animal and human bodies. In addition to the beneficial nutritional properties of mushrooms (mineral elements, favorable proteins, low fat and energy content, pleasant aroma, and flavor), they have a high glucan content. Folk medicine (especially in the Far East) used medicinal mushrooms based on previous experience. At the end of the 19th century, but mainly since the middle of the 20th century, progressively more scientific information has been published. Glucans from mushrooms are polysaccharides that contain sugar chains, sometimes of only one kind (glucose), sometimes having several monosaccharide units, and they have two (α and β) anomeric forms (isomers). Their molecular weights range from 104 to 105 Da, and rarely 106 Da. X-ray diffraction studies were the first to determine the triple helix configuration of some glucans. It seems that the existence and integrity of the triple helix structure are criteria for their biological effects. Different glucans can be isolated from different mushroom species, and several glucan fractions can be obtained. The biosynthesis of glucans takes place in the cytoplasm, the processes of initiation and then chain extension take place with the help of the glucan synthase enzyme complex (EC 2.4.1.34), and the sugar units are provided by sugar donor UDPG molecules. The two methods used today for glucan determination are the enzymatic and Congo red methods. True comparisons can only be made using the same method. Congo red dye reacts with the tertiary triple helix structure, and the resulting glucan content better reflects the biological value of glucan molecules. The biological effect of β-glucan molecules is proportional to the integrity of the tertiary structure. The glucan contents of the stipe exceed the values of the caps. The glucan levels of individual fungal taxa (including varieties) differ quantitatively and qualitatively. This review presents in more detail the glucans of lentinan (from Lentinula edodes), pleuran (from Pleurotus ostreatus), grifolan (from Grifola frondose), schizophyllan (from Schizophyllum commune), and krestin (from Trametes versicolor), along with their main biological effects.

Elucidating thermochemical pretreatment effectiveness of different particle-size switchgrass for cellulosic ethanol production

Effects of switchgrass particle sizes (<0.25 mm, 0.5–1.0 mm, and 2.0–4.0 mm) on the effectiveness of H2SO4 and NaOH pretreatments were investigated. As particle size increased, glucan, xylan, and lignin contents in raw switchgrass augmented from 30.32% to 32.02%, 18.44% to 19.03%, and 14.78% to 15.33%, respectively. Glucan and xylan (58.54–60.94% and 18.55–20.01%) contents in NaOH pretreated switchgrass and their recoveries (91.95–94.69% and 47.91–52.31%) increased. The highest glucan content (55.76%) and recovery (79.72%) in H2SO4 pretreated switchgrass were reached by middle particle size. The lowest (59.39% for H2SO4 and 58.99% for NaOH) and highest (65.23% for H2SO4 and 66.15% for NaOH) CrI values were obtained from middle and small particle sizes, respectively. SEM images and FTIR spectra showed no visible variations in microstructures and chemical bonds among different particle sizes under the same pretreatment conditions. On the basis of pretreated switchgrass, the highest ethanol concentration and efficiency were reached by big particle size for H2SO4 pretreated (7.03 g/L and 49.28%) switchgrass, while they were achieved by small particle size for NaOH pretreated (11.68 g/L and 72.37%) switchgrass. The highest ethanol yield based on raw switchgrass was attained by big particle size for untreated (29.54%), middle particle size for H2SO4 pretreated (30.60%), and small particle size for NaOH pretreated (62.36%) switchgrass. These findings indicate that the optimal ethanol conversion performance is the result of the interaction between the pretreatment method and biomass particle size.

Co-production of xylose, lignin, and ethanol from eucalyptus through a choline chloride-formic acid pretreatment

A choline chloride-formic acid (ChCl-FA) pretreatment followed by enzymatic hydrolysis and fermentation were developed in this work for co-produce bioethanol, xylose, and lignin from eucalyptus. Results showed that ChCl-FA pretreatment can simultaneously degrade the xylan (∼95.2%) and lignin (∼74.4%) in eucalyptus, and obtained the pretreated eucalyptus having high glucan content and a numbers of cracks and holes, which was conducive to follow-up cellulase attacking. The hydrolysis experiments showed the maximum yield of glucose of 100 g eucalyptus was 35.3 g, which was equivalent to 90.3% of glucan in eucalyptus feedstock. The fermentation of enzymatic hydrolysate finally achieved the ethanol yield of 16.5 g, which corresponded to 74.5% theoretical ethanol yield from initial glucan in eucalyptus. In addition, 12.1 g xylose and 23.9 g lignin also could be obtained in pretreated liquid or/and hydrolysis residue, which represented for 61.4% xylan and 80.7% lignin in eucalyptus feedstock, respectively.

Investigation into Lewis and Brønsted acid interactions between metal chloride and aqueous choline chloride-oxalic acid for enhanced furfural production from lignocellulosic biomass

Furfural has been identified as a valuable biobased platform chemical that can be further converted into bioenergy and biochemicals. Furfural is derived from lignocellulosic biomass and can also be regarded as a sustainable alternative to petrochemical products. Herein, the performance of trivalent metal chlorides (FeCl3, AlCl3) and tetravalent metal chlorides (SnCl4, TeCl4) as Lewis acidic cocatalysts was investigated in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent (DES) system for producing furfural from oil palm fronds (OPFs). The metal chlorides with greater electrical field gradients were stronger Lewis acids that enhanced both furfural production and degradation reactions. The main degradation product in this reaction system was humin, and this result was confirmed by FTIR analysis. By subjecting OPFs to an aqueous DES reaction (120 °C, 45 min) with SnCl4 (2.50 wt%), a furfural yield of 59.4% was obtained; without incorporated metal chlorides, the furfural yield was 46.1%. Characterization studies showed synergistic Lewis and Brønsted acid interactions between metal chlorides and DES components. Overall, the residual OPFs showed high glucan content, which led to the production of glucose (71.4%) as a byproduct via enzymatic hydrolysis. Additionally, the aqueous DES system was recycled and reused for several additional runs. The proposed aqueous DES system presents a promising biorefinery approach for the conversion of OPFs to biochemicals.

NaOH-Catalyzed Fractionation of Rice Husk Followed by Concomitant Production of Bioethanol and Furfural for Improving Profitability in Biorefinery

The alkaline fractionation of rice husk (RH) with NaOH was optimized for the purpose of obtaining a high-yield recovery of glucan and increasing the removal rate for lignin and ash, resulting in a hemicellulose-rich hydrolysate. The determined optimal conditions were a temperature of 150 °C, reaction time of 45 min, and NaOH concentration of 6% (w/v). The glucan content in the fractionated RH (Fr. RH) was 80.1%, which was significantly increased compared to the raw RH (35.6%). High glucan content in the fractionated solid residue is the most essential factor for minimizing enzyme dosages in enzymatic saccharification. The final enzymatic digestibilities (at 96 h) of raw and NaOH-Fr. RH with cellulase loadings of 30 FPU/g cellulose were 10.5% and 81.3%, respectively. Approximately 71.6% of the xmg content (mainly xylose) was concomitantly degraded into the fractionated hydrolysate (Fr. Hydrolysate). When this hydrolysate was acidified with sulfuric acid and subjected to heat treatment, a furfural production yield of about 64.9% was obtained. The results show that two-stage fed-batch fermentation with glucan-rich Fr. RH has the potential to achieve high-ethanol titers of 28.7 g/L.

Nonsevere furfural production using ultrasonicated oil palm fronds and aqueous choline chloride-oxalic acid

Furfural is a versatile platform chemical that can be employed to produce green fuel and chemical intermediates. In this study, oil palm fronds were first subjected to ultrasonic pretreatment using an ultrasonic probe in water, which was followed by reaction in an aqueous choline chloride-oxalic acid (16.4 wt% H2O) deep eutectic solvent. The focus of this study was to investigate whether the duration and amplitude of ultrasonic pretreatment improve the furfural yield from oil palm fronds. Mechanoacoustic and sonochemical effects induced by ultrasound waves disrupted the lignin carbohydrate complex in biomass, which increased the hemicellulose availability in the oil palm fronds for furfural production in the subsequent aqueous choline chloride-oxalic acid reaction. By employing ultrasonic pretreatment at 80 % amplitude for 3 min and then an aqueous choline chloride-oxalic acid reaction at 120 °C for 60 min, a furfural yield of 56.5 % was obtained. Characterization studies (e.g., Fourier transform infrared spectroscopy, Brunauer-Emmet-Teller, X-ray diffraction, and field emission scanning electron microscopy) on the oil palm fronds yielded insights into the reaction. Additionally, the reacted oil palm frond residues had a high glucan content, which could be considered a valuable byproduct.

Microstructural and carbohydrate compositional changes induced by enzymatic saccharification of green seaweed from West Africa

The use of marine macroalgae as carbon source for fermentation is gaining increasing attention due to their high carbohydrate content and availability. Three green seaweed species Chaetomorpha linum, Ulva fasciata and Caulerpa taxifolia were investigated for their amenability to enzymatic saccharification. Microstructural changes were studied in order to understand the physical changes occurring in the seaweeds during saccarification and to identify structural barriers. C. linum had highest glucan content (20%), compared to 16% in U. fasciata and 6% in C. taxifolia indicating large differences in composition. Glucose yields obtained after 24 h of enzymatic saccharification were 59, 38 and 60% for C. taxifolia, U. fasciata and C. linum, respectively, based on the glucan content. Pre-autoclaving increased the saccharification yield to 81, 99 and 71%, respectively. Morphologically, C. linum displayed unbranched filaments, U. fasciata two-cell layer large sheets and C. taxifolia featured leaf like structures. Enzymatic saccharification resulted in cell wall degradation and release of the chlorophyll content in C. linum, delamination of sheets in U. fasciata and surface erosion of leaves in C. taxifolia. C. taxifolia deviated in being very rich in β-1,3 linked xylan (46%), which was only hydrolysed at 1% xylose yield due to lack of β-1,3-xylanase. Based on the high cellulose content and no need for pre-treatment C. linum was the best source of glucose among the three types of green seaweed species. Further studies are warranted to assess fermentation. We also conclude that for C. taxifolia enzymatic saccharification with β-1,3-xylanase might enable further xylose release than obtained here with the enzymatic cellulase treatment.

Fractionation and Potential Applications of Components from Microwave Liquefaction of Chromate Copper Arsenate-Treated Wood

Decommissioned chromate copper arsenate (CCA)-treated wood poles were subjected to a microwave liquefaction process. The liquefied products were separated into cellulosic component, lignin fractions, and spent liquor. Analysis of the distribution of the CCA elements showed that the resulting cellulosic component and lignins were detoxified. Compared with the CCA-treated wood, the fractionated detoxified cellulosic component had become micro-sized and had a higher glucan content, crystallinity, and glucose conversion yield, as well as a larger surface area. Thus, the detoxified cellulosic component has potential as a raw material for biorefinery usage or for cellulosic material reinforced composite production. The constituents, such as glucose, xylose, glycerol, and their derivatives, as well as the metal elements in the spent liquor, are appropriate ingredients for the preparation of antifungal and insect resistant polyurethane foams. The fractionated detoxified cellulosic component and lignin products, in addition to the potential application for the spent liquor in the polyurethane industry, confirmed that the microwave liquefaction process coupled with a fractionation procedure is an environmentally conscious approach for the integrated utilization of decommissioned chromate copper arsenate treated wood.

Enzymatic response to structural and chemical transformations in Hibiscus sabdariffa var. altissima bark and core during phosphoric acid pretreatment

To investigate the potential of Hibiscus sabdariffa var. altissima (Thai kenaf) biomass as a feedstock for bioethanol production, Thai kenaf bark and core were pretreated at a moderate temperature with different phosphoric acid (H3PO4) concentrations. It was revealed that there was a higher glucan content in the Thai kenaf bark (57.97% ± 0.36%) compared with that in the core (43.10% ± 0.15%). The H3PO4 pretreatment resulted in a reduction in the lignin content and total removal of hemicellulose. This exposed the cellulose to attack by cellulase enzymes and resulted in an increased enzymatic digestibility. A high glucose concentration (GC; 7.02 g/L) and hydrolysis efficiency (HE; 95.79%) were achieved with 75% H3PO4 for the bark after 72 h of enzymatic hydrolysis. However, these values were not that different from those of the 70% H3PO4-pretreated bark (6.89 g/L and 95.43%, respectively). Nevertheless, the Thai kenaf core pretreated with 75% H3PO4 recorded a higher GC (6.30 g/L) and HE (91.67%) after 72 h of enzymatic hydrolysis. The scanning electron microscopy and X-ray diffraction analyses revealed the destruction of the surface structure and an increase in the porosity and crystallinity index of the Thai kenaf biomass, which corresponded to an increased enzymatic digestibility.

Tension wood structure and morphology conducive for better enzymatic digestion

BackgroundTension wood is a type of reaction wood in response to bending or leaning stem as a corrective growth process. Tension wood is formed by both natural and man-made processes. Most attractively, tension wood contains higher glucan content and undergoes higher enzymatic conversion to fermentable sugars. Here, we have employed structural techniques, small-angle neutron scattering (SANS) and wide-angle X-ray diffraction (WAXD) to elucidate structural and morphological aspects of tension wood conducive to higher sugar yields.ResultsSmall-angle neutron scattering data exhibited a tri-modal distribution of the fibril cross-sectional dimension. The smallest size, 22 Å observed in all samples concurred with the WAXD results of the control and opposite side samples. This smallest and the most abundant occurring size was interpreted as the cellulose elementary microfibril diameter. The intermediate size of 45 Å, which is most pronounced in the tension side sample and consistent with WAXD results for tension side sample, indicates association of neighboring elementary microfibrils to form larger crystallite bundles. The largest size 61 Å observed by SANS was however not observed by WAXD and therefore associated to mesopores.ConclusionsStructure and morphology of tension wood is different from control wood. Cellulose crystallinity increases, lignin content is lower and the appearance of mesopores with 61 Å diameter is observed. Despite the presence of higher crystalline cellulose content in tension side, the lower lignin content and may be combined with the abundance of mesopores, substantially improves enzyme accessibility leading to higher yields in cellulose digestion.

Assessment of the Influence of the Temperature in the Microwave-Assisted Alkaline Delignification of Vine Shoots

The limitation of the fossil-resources has led the research to focus on the production of biomass-based fuels from lignocellulosic agricultural residues, as it is the case of the bio-ethanol. Due to the complex and heterogeneous structure of these residues, a delignification stage is usually necessary prior to a simultaneous saccharification and fermentation treatment (SSF) for the production of bio-ethanol. In a previous work, an alkaline delignification of hydrothermally pretreated vine shoots using conventional heating was carried out in order to obtain a solid residue with low lignin and hemicellulosic content, which could be further subjected to a SSF treatment. However, when this biorefinery scheme was evaluated by a Life Cycle Assessment it was observed that the energy and chemical requirements of the delignification stage needed to be reduced. Therefore, in this work the assistance of the alkaline delignification stage by microwave was studied. The treatments were carried out at different temperatures, in order to study its influence on the lignin removal. It was observed that the microwave assistance could permit the improvement of the delignification treatments not only by increasing the delignification yield but also by reducing the temperature, time and NaOH concentration used in the treatments. The strong influence of the temperature on the chemical composition, structure and crystallinity of the delignified solids was also appreciated during this study. The solid residues obtained under the most severe conditions of the microwave-assisted alkaline delignification treatment (125 °C) could be a promising solid for the employment in a SSF treatment due to its low lignin and hemicellulosic content (16.68 % and 0.01 % respectively) and its high glucan content (50.75 %), although it presented a higher crystallinity index than the hydrothermally pretreated vine shoots.

Hydrothermal Treatments of Cistus ladanifer Industrial Residues Obtained from Essential Oil Distilleries

The aim of this study was to optimize hydrothermal treatments (autohydrolysis) for selective hydrolysis of hemicelluloses in the residues obtained from the industrial steam distillation of Cistus ladanifer (rock-rose) for essential oil extraction (CLR). The effect of the autohydrolysis in the removal of extractives of these residues was also evaluated. The raw material was treated with water in a 6:1 liquid-to-solid ratio (w/w) and the effect of temperature (130–230 °C) on the composition of liquid and solid phases were evaluated and interpreted using the severity factor (log R0). The highest recovery of oligosaccharides (24.7 g/L), corresponding to a yield of 28.4 g/100 g of CLR was obtained at moderate conditions, log R0 of 3.12. Together with hemicelluloses, polar extracts were also largely solubilized during the hydrothermal process yielding hydrolysates with a relevant concentration of phenolics. The highest glucan content (35.6 g/100 g of CLR) of the solid residue was obtained at more severe conditions, log R0 of 4.0 (220 °C). There was no apparent lignin solubilisation in any of the conditions, which is an advantage of this hydrolytic pretreatment. Cistus ladanifer residues demonstrated to have potential to be used in the biorefinery framework with a full upgrade of all biomass fractions.

Olive Mill Waste Enhances α-Glucan Content in the Edible Mushroom Pleurotus eryngii.

Mushroom polysaccharides are edible polymers that have numerous reported biological functions; the most common effects are attributed to β-glucans. In recent years, it became apparent that the less abundant α-glucans also possess potent effects in various health conditions. Here we explore several Pleurotus species for their total, β and α-glucan content. Pleurotus eryngii was found to have the highest total glucan concentrations and the highest α-glucans proportion. We also found that the stalks (stipe) of the fruit body contained higher glucan content then the caps (pileus). Since mushrooms respond markedly to changes in environmental and growth conditions, we developed cultivation methods aiming to increase the levels of α and β-glucans. Using olive mill solid waste (OMSW) from three-phase olive mills in the cultivation substrate. We were able to enrich the levels mainly of α-glucans. Maximal total glucan concentrations were enhanced up to twice when the growth substrate contained 80% of OMSW compared to no OMSW. Taking together this study demonstrate that Pleurotus eryngii can serve as a potential rich source of glucans for nutritional and medicinal applications and that glucan content in mushroom fruiting bodies can be further enriched by applying OMSW into the cultivation substrate.

Coproduction of Furfural and Easily Hydrolyzable Residue from Sugar Cane Bagasse in the MTHF/Aqueous Biphasic System: Influence of Acid Species, NaCl Addition, and MTHF

In order to develop a process for the simultaneous production of furfural and easily hydrolyzable cellulose, the degradation of sugar cane bagasse in a single aqueous system and in a 2-methyltetrahydrofuran (MTHF)/aqueous AlCl3 biphasic system was studied. In single aqueous system, the influence of acid species (FeCl3, HCl, and AlCl3) on furfural production and cellulose degradation was investigated at 150 °C. FeCl3 and HCl promoted furfural production from hemicellulose but with severe cellulose degradation. AlCl3 decreased cellulose degradation with considerable furfural yield and high glucan content in solid residues. The role of NaCl in furfural production and cellulose decomposition was also investigated in the single aqueous system using different acids as catalysts. Addition of NaCl significantly promoted furfural yield but also accelerated cellulose decomposition when FeCl3 or HCl was used as catalyst. In the AlCl3-catalyzed system, NaCl had less influence on residue yield and its composition, alt...

Life cycle assessment of common reed (Phragmites australis (Cav) Trin. ex Steud) cellulosic bioethanol in Jiangsu Province, China

Common reed (Phragmites australis (Cav) Trin. ex Steud) at wetlands is a natural resource in Jiangsu Province, China. Proper application of common reed could supplement bioenergy feedstocks and encourage wetlands conservation in this area. In this study, common reed and soil samples from wetlands near to farm, coastline and for wastewater treatment were collected. Potential bioethanol yield was estimated based on biomass yield and bioethanol production, and a life cycle assessment (LCA) model was built to analyze environmental performance of common reed bioethanol. The dry biomass yield of common reed was in the range of 3.8–36 Mg ha−1, and location was the significant factor on biomass yield. Soil pH and available N content had positive impacts on yields of biomass and bioethanol; higher glucan content was detected in stem than in leaf and flower, while ash and klason lignin contents were higher in leaf than in stem and flower. The results indicated that wetlands with high available N content were very suitable for common reed growth, and stem fraction was better than leaf for bioethanol production. Based on LCA model calculation, the net energy and ratio of energy efficiency were compatible to bioethanol from switchgrass and rice straw, and the greenhouse gases (GHG) emission intensity and eutrophication potential were 15 gCO2,eq MJ−1 and −1.1 gPO43−eq MJ−1. The results indicate that common reed is a sustainable and renewable resource for bioethanol production, especially those grown on wetlands near to farmland in Jiangsu Province, China.

Enzymatic hydrolysis of chemically pretreated mango stem bark residues at high solid loading

In the present work, the solid residues of mango stem bark after maceration (MSBAM) were studied as a lignocellulosic material with the potential of serving as a feedstock in the field of bioenergetics. The efficiency of two different chemical pretreatments was evaluated using dilute phosphoric acid and sodium hydroxide. The influence of solid:liquid ratio (w/v), temperature and residence time was assessed on chemical characterization of the pretreated solid fraction of MSBAM. The conversion of glucan to glucose was assessed by enzymatic hydrolysis. Alkaline pretreatment at 120°C, 15min and solid: liquid ratio (1:10) was the selected condition for obtaining high glucan content. Also, the enzymatic hydrolysis at high-solids loadings was studied. The results of the enzymatic hydrolysis at 21% showed a glucose production of 71.2g/L, which corresponds to 56.3% of the enzymatic hydrolysis yield. However, at 15% of solid loading, the glucose concentration obtained was 48.9g/L and the enzymatic hydrolysis yield was 75.3%. MSBAM has been considered as a raw material, due to its lignocellulosic structure, susceptible to enzymatic attack for obtaining sugars which, in turn, can be converted into ethanol and other products. Using Scanning Electron Microscopy (SEM), visualization of fibers was done for all the solids pretreated.

Brown seaweed processing: enzymatic saccharification of Laminaria digitata requires no pre-treatment

This study assesses the effect of different milling pre-treatments on enzymatic glucose release from the brown seaweed Laminaria digitata having high glucan (laminarin) content. Wet refiner milling, using rotating disc distances of 0.1–2 mm, generated populations of differently sized pieces of lamina having decreasing average surface area (100–0.1 mm2) with increased milling severity. Higher milling severity (lower rotating disc distance) also induced higher spontaneous carbohydrate solubilization from the material. Due to the seaweed material consisting of flat blades, the milling did not increase the overall surface area of the seaweed material, and size diminution of the laminas by milling did not improve the enzymatic glucose release. Milling was thus not required for enzymatic saccharification because all available glucose was released even from unmilled material. Treatment with a mixture of alginate lyase and a cellulase preparation (Cellic®CTec2) on large-sized milled material released all available glucose within 8 h. Application of the cellulase preparation alone released only half of the available glucose. The alginate lyase catalysis apparently induced selective removal of alginate to improve the cellulase catalyzed degradation of laminarin and cellulose in the material.

Variability in composition of individual botanical fractions of Miscanthus × giganteus and their blends

Biorefineries require a consistent biomass feedstock to ensure optimal processing efficiency and a convenient method to evaluate biomass delivered at the factory gate. The combination of fractionation, selective blending of biomass streams, and densification is one strategy of ensuring feedstock with uniform quality attributes. In this study, dry mass fraction and compositional variability of botanical fractions of Miscanthus × giganteus harvested post-senescence were determined. Fourier transform near infrared (FT-NIR) spectroscopy was used to monitor composition of blends. Results showed that the majority of miscanthus stalks were composed of rind (48–63%) followed by sheath (17–28%), nodes (10–16%), and pith (8–13%). Rind had the highest glucan content (46.1%) while lignin content was highest in node (25.5%) and rind fractions (24.2%). Ash content was highest in blade fractions (8.9%) and was less than 1% in rind, pith, and nodes. Variability in composition was reflected in the 4250–4350 cm−1 and 5500–6000 cm−1 regions of the botanical fractions' FT-NIR spectra. Principal components analysis (PCA) of FT-NIR spectra of rind-blade blends were useful in screening blends based on structural carbohydrates, lignin and ash contents demonstrating the use of NIR spectroscopy in monitoring feedstock formulation.

Analysis, pretreatment and enzymatic saccharification of different fractions of Scots pine

BackgroundForestry residues consisting of softwood are a major lignocellulosic resource for production of liquid biofuels. Scots pine, a commercially important forest tree, was fractionated into seven fractions of chips: juvenile heartwood, mature heartwood, juvenile sapwood, mature sapwood, bark, top parts, and knotwood. The different fractions were characterized analytically with regard to chemical composition and susceptibility to dilute-acid pretreatment and enzymatic saccharification.ResultsAll fractions were characterized by a high glucan content (38-43%) and a high content of other carbohydrates (11-14% mannan, 2-4% galactan) that generate easily convertible hexose sugars, and by a low content of inorganic material (0.2-0.9% ash). The lignin content was relatively uniform (27-32%) and the syringyl-guaiacyl ratio of the different fractions were within the range 0.021-0.025. The knotwood had a high content of extractives (9%) compared to the other fractions. The effects of pretreatment and enzymatic saccharification were relatively similar, but without pretreatment the bark fraction was considerably more susceptible to enzymatic saccharification.ConclusionsSince sawn timber is a main product from softwood species such as Scots pine, it is an important issue whether different parts of the tree are equally suitable for bioconversion processes. The investigation shows that bioconversion of Scots pine is facilitated by that most of the different fractions exhibit relatively similar properties with regard to chemical composition and susceptibility to techniques used for bioconversion of woody biomass.

Chemical characterization and hydrothermal pretreatment of Salicornia bigelovii straw for enhanced enzymatic hydrolysis and bioethanol potential

Salicornia bigelovii straw was characterized and evaluated as a potential lignocellulosic bioethanol feedstock. S. bigelovii used in the study was grown in the United Arab Emirates using saltwater (40ppt) for irrigation. Salt removal was performed prior to pretreatment to protect the processing equipment and avoid inhibition of enzymes and yeast. Composition of the washed biomass was comparable to traditional lignocellulosic biomasses with relatively high glucan and xylan content (26 and 22g/100gDM, respectively) but with lower lignin content (7g/100gDM). The washed feedstock was subjected to hydrothermal pretreatment, producing highly digestible (up to 92% glucan-to-glucose conversion) and fermentable (up to 100% glucose-to-ethanol conversion) fiber fractions. Liquid fractions obtained in the pretreatment did not show inhibition towards Saccharomyces cerevisiae. No significant differences among the enzymatic convertibility and microbial fermentability of the fibers as well as low xylose recoveries suggest that lower severity pretreatment conditions could be exploited for S. bigelovii.