Xylooligosaccharides Yield Research Articles

An integrated biorefinery process for adding values to corncob in co-production of xylooligosaccharides and glucose starting from pretreatment with gluconic acid

Increasing attention has been paid to the production of high value-added products from lignocellulosic biomass. This study aims to valorize corncob, utilizing it as feedstock for a multi-biorefinery framework, using gluconic acid in the pretreatment. In attempts to maximize yield of xylooligosaccharides, corncob was first subjected to hydrolysis by gluconic acid using response surface methodology, from which the maximum xylooligosaccharides yield of 56.2% was achieved using 0.6 mol/L gluconic acid at 154 °C for 47 min. Results indicated that gluconic acid was an effective solvent for xylooligosaccharides production: a total of 180 g of xylooligosaccharides was obtained from 1 kg corncob as a result of hydrolysis. Moreover, 86.3% conversion of cellulose was achieved from enzymatic hydrolysis of gluconic acid-treated corncob at 10% solids loading. This study presents a strategy for valorizing corncob using it to produce xylooligosaccharides and glucose, which should pave the way for valorizing other agriculture wastes.

Co-production of xylooligosaccharides and activated carbons from Camellia oleifera shell treated by the catalysis and activation of zinc chloride

Camellia oleifera shell (COS) is a worthy byproduct in woody edible oil production enriched in hemicellulose and lignin. This paper aims to explore the high-value transformation of COS for the production of xylooligosaccharides (XOS) with main degree of polymerization (DP) of 2–5 by the catalysis of ZnCl2. The effect of pretreatment temperature, reaction time and ZnCl2 concentration on the contents and DP distributions of XOS were analyzed. Moderate reaction conditions tended to achieve high content XOS, and the maximum value 61.38% and 14.39 g/L of XOS yield and concentration, respectively, peaked at 170 °C for 30 min using 0.5% (w/w) ZnCl2. The first time the solid residues derived from the production process of XOS were used as the precursor for the co-production of activated carbons (AC). The maximum iodine values and BET surface area were 5623.94 mg/g and 1244.46 m2/g, respectively, using 2.20 M ZnCl2 as the activating agent.

Comparison of selective acidolysis of xylan and enzymatic hydrolysability of cellulose in various lignocellulosic materials by a novel xylonic acid catalysis method

An economically-prudent pretreatment is a crucial first step towards realization of the industrial lignocellulosic biorefinery. The aim of this study was to utilize lignocellulosic biomass to co-produce xylo-oligosaccharides (XOS) and glucose starting from a novel self-providing xylonic acid (XA) acidolysis method. Based on the optimization results of main acidolysis pretreatment parameters by uniform design experiments, we found that among various lignocellulosic materials, the highest yield of XOS from xylan was 54.16% with corncob, followed by 39.19% with wheat straw, 29.01% with corn straw and 30.23% with poplar sawdust. By effective degradation and removal of xylan constituents with XA acidolysis, enzymatic hydrolysabilities of inert cellulose constituents of corn cob, corn straw, wheat straw and poplar sawdust were achieved to 100%, 72.94%, 75.35% and 38.97%. Comparative mass balance diagrams of xylan and cellulose reveal that XA acidolysis pretreatment is environmental-friendly and effective for three agricultural residues, apart from woody poplar.

Integrated production of prebiotic xylooligosaccharides and high value cellulose from oil palm biomass

Oil palm empty fruit bunch (OPEFB) fibre, which is the byproduct of fruits being stripped from the fresh fruit bunch in palm oil mill, was evaluated in terms of the production of xylooligosaccharides (XOs) and the solid residue was treated for cellulose recovery. Chemoenzymatic hydrolysis that consists of chemical fractionation of OPEFB fibre to isolate xylan with further enzymatic hydrolysis to XOs in a packed bed column reactor (PBCR) was performed. An immobilised xylanase of Thermomyces lanuginosus at the concentration of 8.25 fungal xylanase unit wheat/mililitre (FXUW mL−1) was employed on a PBCR to hydrolyse the xylan at 55 °C and pH 5.5. The yields of XOs are composed of xylopentaose, xylotetraose, xylotriose and xylobiose, successfully produced from the OPEFB-xylan, shown in HPLC analysis with the total production of 8,776 mg/L and the immobilised xylanase can be recycled up to six enzymatic treatment cycles. The solid residue generated from the xylan extraction was further treated with mild concentration of bleaching agents of 20% (v/v) formic acid and 5% (v/v) hydrogen peroxide at 85 °C. The Fourier transform infrared spectroscopy (FTIR) analysis showed that the products obtained have the standard cellulose structure and functional group. Further analyses on the properties of the extracted cellulose in terms of crystallinity, thermal stability and morphology were conducted. The integrated process to produce XOs from OPEFB and recover cellulose from its byproduct is sustainable to extract fine chemicals from OPEFB.

Novel approach to produce biomass-derived oligosaccharides simultaneously by recombinant endoglucanase from Trichoderma reesei

The recombinant endoglucanase gene (EG I) from Trichoderma reesei was successfully expressed in Pichia pastoris for the purpose of producing oligosaccharides from various biomass-derived substrates. Interestingly, the recombinant endoglucanase I (ReEG I) showed the catalytic activity towards both cellulose and xylan hydrolysis, yet it was more efficient with xylans. Among various glucans and xylans substrates (paper pulp, carboxymethylated cellulose, oat spelt xylan, birchwood xylan), birchwood xylan displayed a higher yield of xylooligosaccharides (XOS) (69.5 % after optimization). Eventually, it was observed that ReEG I could simultaneously produce XOS and COS, when the alkali-extracted corncob residues were used as substrate. This is the first report on simultaneous production of XOS and COS by recombinant endoglucanase I from Trichoderma reesei expressed in Pichia pastoris, where a novel application of genetically engineered enzymes is proposed to provide an attractive application for high value utilization of biomass.

Optimization of selective acidolysis pretreatment for the valorization of wheat straw by a combined chemical and enzymatic process

AbstractBACKGROUNDAdvances in industrial biotechnology offer potential opportunities for economic utilization of abundantly available agricultural crop waste such as wheat straw, which is of great interest for advancement in xylo‐oligosaccharides (XOS) and fermentable monosaccharides. In the present study, crude XOS and fermentable monosaccharides were sequentially produced by a combined chemical and enzymatic process from wheat straw.RESULTSMaximum yield of XOS was 38.2% and the corresponding yield of glucose was 82.7% despite the wax barrier on the surface of wheat straw, while the acetic acid concentration was decreased from 20% to 5%. Pilot scale run produces 91.6 g XOS, 92.5 g xylose and 316.0 g glucose from 1000 g of wheat straw that means the utilization of 78.9% of xylan and 89.7% glucan constitutes.CONCLUSIONBy removal of 65% xylan from wheat straw, enzymatic hydrolysis of cellulose was also improved efficiently although its polymer structure was almost kept inert during acetic acid pretreatment. © 2019 Society of Chemical Industry

Eco-friendly consolidated process for co-production of xylooligosaccharides and fermentable sugars using self-providing xylonic acid as key pretreatment catalyst

BackgroundObtaining high-value products from lignocellulosic biomass is central for the realization of industrial biorefinery. Acid pretreatment has been reported to yield xylooligosaccharides (XOS) and improve enzymatic hydrolysis. Moreover, xylose, an inevitable byproduct, can be upgraded to xylonic acid (XA). The aim of this study was to valorize sugarcane bagasse (SB) by starting with XA pretreatment for XOS and glucose production within a multi-product biorefinery framework.ResultsSB was primarily subjected to XA pretreatment to maximize the XOS yield by the response surface method (RSM). A maximum XOS yield of 44.5% was achieved by acid pretreatment using 0.64 M XA for 42 min at 154 °C. Furthermore, XA pretreatment can efficiently improve enzymatic digestibility, and achieved a 90.8% cellulose conversion. In addition, xylose, the inevitable byproduct of the acid-hydrolysis of xylan, can be completely converted to XA via bio-oxidation of Gluconobacter oxydans (G. oxydans). Subsequently, XA and XOS can be simultaneously separated by electrodialysis.ConclusionsXA pretreatment was explored and exhibited a promising ability to depolymerize xylan into XOS. Mass balance analysis showed that the maximum XOS and fermentable sugars yields reached 10.5 g and 30.9 g per 100 g raw SB, respectively. In summary, by concurrently producing XOS and fermentable sugars with high yields, SB was thus valorized as a promising feedstock of lignocellulosic biorefinery for value-added products.

Production of xylooligosaccharides and monosaccharides from hydrogen peroxide-acetic acid-pretreated poplar by two-step enzymatic hydrolysis

The severe pretreatment of poplar makes xylan difficult to utilize efficiently. In this work, poplar was pretreated by hydrogen peroxide–acetic acid (HPAC) with H2SO4 as catalyst to remove lignin, and the solid residues were used to produce xylooligosaccharides (XOS) and monosaccharides by two-step xylanase and cellulase hydrolysis. The results indicated that higher H2SO4 concentrations in the HPAC pretreatment of poplar afforded stronger lignin removal ability. An increased XOS yield of 19.8% was obtained from 200 mM H2SO4-catalyzed poplar by xylanase and the XOS purity was high, with a very low xylose/XOS ratio of 0.14. Higher glucose (75.2%) and xylose (61.4%) yields were obtained from the HPAC-pretreated poplar using 50 mM H2SO4 as catalyst. Finally, 16.9 g XOS and 296.4 g glucose were produced from 1 kg poplar by xylanase and cellulase. This study provides a method for producing functional XOS and monosaccharides from poplar using a simple reduced-pollution strategy.

Biochemical characteristics of the mutant xylanase T-XynC(122)C(166) and production of xylooligosaccharides from corncobs

The thermostable recombinant xylanase, T-XynC(122)C(166), was investigated for its biochemical characteristics and capacity to produce xylooligosaccharides from corncobs pretreated through auto-hydrolysis. T-XynC(122)C(166) showed optimal activity at pH 6.5 and 75 °C, and is an acidophilic and thermostable xylanase with a Km of 6.08 mg/mL towards beechwood xylan. Hydrolysis of xylan into xylooligosaccharides was through an endohydrolytic mode of action. Although xylotriose and xylobiose were the main hydrolysates produced from different xylans by T-XynC(122)C(166), their compositions and yields were substrate dependent. T-XynC(122)C(166) showed the highest degradation efficiency towards beechwood xylan, followed by oat-spelt xylan and birchwood xylan. T-XynC(122)C(166) rapidly hydrolyzed xylotetraose into xylotriose and xylobiose through transglycosylation, whereas xylotriose was hydrolyzed slowly and xylobiose was not hydrolyzed. The xylooligosaccharide yield from corncobs was determined to be 26.4% when treated with T-XynC(122)C(166) (5 U/mL) at pH 5.5 and 50 °C for 2 h, indicating its high potential for xylooligosaccharide production from agricultural waste.

Co-catalysis of magnesium chloride and ferrous chloride for xylo-oligosaccharides and glucose production from sugarcane bagasse

Inorganic salt treatment is a novel, high-yield, and environmentally friendly approach for the production of xylo-oligosaccharides from Sugarcane bagasse with degree of polymerization of 2–5. A xylo-oligosaccharides yield of 53.79% was obtained with 0.1 M MgCl2 treatment at 180 °C/10 min, and 41.89% with 0.1 M FeCl2 treatment at 140 °C/30 min. The xylo-oligosaccharides yield from the co-catalysis of 0.05 M FeCl2 + 0.05 M MgCl2 reached 54.68% (29.34% xylobiose and 20.94% xylotriose) at 140 °C/30 min. The co-catalysis not only effectively improved the xylobiose and xylotriose contents but also increased the total yield of xylo-oligosaccharides under mild reaction conditions. Additionally, the glucose yield observed from the solid residue after inorganic salt treatment was 71.62% by enzymatic hydrolysis. Mg2+ and Fe2+ are essential for good human health without separation from the system, therefore, the inorganic salt treatment can be potentially applied in the co-production of xylo-oligosaccharides and glucose.

Production of prebiotic xylooligosaccharide from aqueous ammonia-pretreated rice straw by β-xylosidase of Weissella cibaria.

This study focuses on the development of a new strategy xylooligosaccharide (XOS) production from aqueous ammonia-pretreated rice straw (A-PRS), followed by β-xylosidase hydrolysis produced by the newly identified strain Weissella cibaria FB069. We report a higher efficiency of A-PRS, including the removal of lignin and increase in cellulose and xylan content, compared to that of the alkali and stream explosion methods. Using the ammonia pretreatment method, rice straw was used to obtain 32·4% xylan. The crude xylanase from W. cibaria was used to hydrolyse A-PRS over different hydrolysis times. The highest XOS yield (131mg XOS per gram rice straw) was observed after 10h. XOS produced from the PRS was tested on stimulation effect on Bifidobacterium and Lactobacillus. The possibility of XOS production from PRS using β-xylosidase with strong prebiotic properties. We investigated the new strain for signification production of XOS. The two-stage process here described could help to further explore the optimization conditions for prebiotic production. Additionally, the stimulation effect of XOS from alternative source has a promising prospect in functional food.

Production of xylooligosaccharides and monosaccharides from poplar by a two-step acetic acid and peroxide/acetic acid pretreatment

BackgroundPopulus (poplar) tree species including hybrid varieties are considered as promising biomass feedstock for biofuels and biochemicals production due to their fast growing, short vegetative cycle, and widely distribution. In this work, poplar was pretreated with acetic acid (AC) to produce xylooligosaccharides (XOS), and hydrogen peroxide–acetic acid (HPAC) was used to remove residual lignin in AC-pretreated poplar for enzymatic hydrolysis. The aim of this work is to produce XOS and monosaccharides from poplar by a two-step pretreatment method.ResultsThe optimal conditions for the AC pretreatment were 170 °C, 5% AC, and 30 min, giving a XOS yield of 55.8%. The optimal HPAC pretreatment conditions were 60 °C, 2 h, and 80% HPAC, resulting in 92.7% delignification and 87.8% cellulose retention in the AC-pretreated poplar. The two step-treated poplar presented 86.6% glucose yield and 89.0% xylose yield by enzymatic hydrolysis with a cellulases loading of 7.2 m/g dry mass. Very high glucose (93.8%) and xylose (94.6%) yields were obtained with 14.3 mg cellulases/g dry mass. Both Tween 80 and β-glucosidase enhanced glucose yield of HPAC-pretreated poplar by alleviating the accumulation of cellobiose. Under the optimal conditions, 6.9 g XOS, 40.3 g glucose, and 8.9 g xylose were produced from 100 g poplar.ConclusionsThe AC and HPAC pretreatment of poplar represented an efficient strategy to produce XOS and fermentable sugars with high yields. This two-step pretreatment was a recyclable benign and advantageous scheme for biorefinery of the poplar into XOS and monosaccharides.

Integrative process for sugarcane bagasse biorefinery to co-produce xylooligosaccharides and gluconic acid

An integrated and green process for co-producing xylooligosaccharides (XOS) and gluconic acid (GA), was developed by utilizing sugarcane bagasse as starting material. In this study, the highest XOS yield of 39.1% obtained from the prehydrolysis was achieved with 10% acetic acid at 150 °C for 45 min. Subsequently, 88.6% conversion of cellulose was achieved in a fed-batch enzymatic hydrolysis using a solid loading of 15%. Results of glucose fermentation suggested that inherent regulatory system of strain Gluconobacter oxydans ATCC 621H boosted GA accumulation without the requirement of pH control, leading to a good 96.3% of GA yield. Great performance of this strain offer an economically feasible option for the large-scale sustainable GA production from biomass. Overall, approximately 105 g XOS and 340 g GA were co-produced from 1 kg of dried sugarcane bagasse as feedstock; this integrated process might be a cost-effective option for the comprehensive utilization of sugarcane bagasse.

Totally chlorine-free bleaching of prehydrolysis soda pulp from plantation hardwoods consisting of various lignin structures

The process of prehydrolysis followed by soda-anthraquinone (AQ) cooking and totally chlorine-free (TCF) bleaching with peroxymonosulfuric acid (Psa) was investigated to develop a biorefinery process. Eucalyptus globulus, showing a high syringaldehyde (Sa) to vanillin (Va) molar ratio after nitrobenzene oxidation, was utilized. Xylooligosaccharide yield in the prehydrolysate (PHL) obtained at 150 °C for 2.5 h reached 7.2% of wood weight, indicating 47% extraction of xylan. Furfural yields increased with acid catalytic dehydration of the PHL to 1.0–1.8% of wood weight; adding an earlier acid post-hydrolysis of the PHL to generate monomeric xylose enhanced furfural production to 4.0%. Soda-AQ cooking, a non-sulfur process affording simpler alkali lignin isolation than kraft cooking, was utilized. Active alkali dosage increment decreased both Sa to Va molar ratio (S/V ratio) and Sa and Va yields of dissolved lignin. Gel permeation chromatography indicated decreased or increased purified lignin weight-average molecular weight (Mw) upon increased active alkali dosage or prehydrolysis temperature, respectively (e.g., 150 to 170 °C at 18% alkali increased Mw 1653 to 2050). Chlorine dioxide (0.083% and 0.042% as active chlorine) inclusion during the 1st and 2nd Psa stages with Psa (0.2% and 0.1% as H2SO5 weight, respectively) improved final bleached pulp viscosity from 6.0 to 7.2 mPa s.

A waste-minimized biorefinery scenario for the hierarchical conversion of agricultural straw into prebiotic xylooligosaccharides, fermentable sugars and lithium-sulfur batteries

How to exert the value-added superiority was a key link in the development of biomass valorization that heightens an appeal for a waste-minimized protocol. The fractional use of three building blocks in biomass became an urgent challenge to be faced. Herein, we report an autohydrolysis-aided biorefinery for the sequential conversion of wheat straw hemicelluloses, cellulose and lignin into xylooligosaccharides (XOS), fermentable glucose and lithium-sulfur cathode at the end of the process, respectively. The yield of XOS (DP of 2–6) reached up to 24.06% (w/w) of xylan and 6.19% (w/w) of the initial biomass. The hydrothermal treatment removed the amorphous portion and disrupted the rigid structure, thereby improving the cellulose digestibility from 14.1 to 88.9%. The molecular weights, functional groups and structural features of residual lignin after enzymatic hydrolysis were thoroughly explored for the cathode of lithium-sulfur batteries via the carbonizing process. Because of the considerable surface area, the covalent linkage between the lignin-derived carbon (LC) and sulfur, and the uniform dispersion of sulfur particles, the developed LC@S cathode exhibited excellent rate capability, and the specific capacity of 1238, 1085 and 1035 mA h g−1 at 0.1, 0.2 and 0.5 C, respectively. The LC@S cathode retained 596 mA h g−1 after 200 cycles at 0.5 C with a coulombic efficiency of 92%. The present study provides a systematic strategy that bears the primary responsibility for exploiting biomass into a potential feedstock with worthwhile functions in the thriving domains of chemicals, biofuels and energy storage devices.

Evaluating the production of monosaccharides and xylooligosaccharides from the pre-hydrolysis liquor of kraft pulping process by acid and enzymatic hydrolysis

Pre-hydrolysis liquor (PHL) from the kraft-based dissolving pulp process contains large amounts of hemicelluloses and their degradation products, which makes it a promising candidate for the production of xylose or xylooligosaccharides (XOS). However, it is usually treated as wastewater of the pulp and paper industries. In this study, both acid hydrolysis and enzymatic hydrolysis were applied to prepare xylose and XOS from the PHL, which contained 47.80 g/L of sugars and 14.10 g/L of lignins. Results showed that an optimal xylose yield (30.10 g/L) was obtained at 120 °C for 0.5 h with 4% aqueous sulfuric acid, while the maximum XOS yield (11.63 g/L) was achieved with 0.3% aqueous sulfuric acid at 120 °C for 2.0 h. For the enzymatic hydrolysis, the highest XOS yield of 15.65 g/L was obtained under the optimal condition (60 IU/L PHL, 50 °C, 6 h), and the XOS were mainly composed of xylobiose and xylotriose.

Enhanced Xylooligosaccharides Yields and Enzymatic Hydrolyzability of Cellulose using Acetic Acid Catalysis of Poplar Sawdust

To increase the value and promote the utilization of woody processing residues, poplar sawdust was used to produce xylooligosaccharides (XOS) with polymerization degrees of 2–6 by acetic acid catalysis. This process is considered to be an environmental friendly process, and the remaining solid fraction was decomposed to fermentable sugars by enzymatic hydrolysis. Response surface methodology (RSM) was applied to determine the main factors affecting the yield of XOS. XOS production was optimal at 170 ± 3 °C with a 6.5 ± 1% acetic acid concentration and 27 ± 2 min reaction time. These conditions produced a 36.0 ± 0.8% XOS yield from xylan, similar to the predicted value from the model. Careful analysis of the kinetic profile of XOS revealed that xylobiose to xylohexaose were the main products. Detectable degraded chemicals accounted for 71.0% xylan during acidic hydrolysis. When using enzymatic hydrolysis at a cellulase loading of 20 FPU/g cellulose, a 51.0% yield was achieved, which represented an 80% increase relative to pretreated autohydrolysis (28.3%), and reached production yields similar to that of diluted sulfuric acid pretreatment.

Acetyl-assisted autohydrolysis of sugarcane bagasse for the production of xylo-oligosaccharides without additional chemicals

The aim of this work was to study acetyl-assisted autohydrolysis of sugarcane bagasse for the production of xylo-oligosaccharides without additional chemicals. A xylo-oligosaccharide yield of 50.35% was obtained in 10 min through sugarcane bagasse autohydrolysis at 200 °C; this yield was 49.64% after acetyl-assisted autohydrolysis of a 65:35 mixture of sugarcane bagasse/white birch at 160 °C for 100 min. The yield of xylo-oligosaccharides was close to that obtained at 180 °C/40 min and 200 °C/10 min through the autohydrolysis of sugarcane bagasse. Compared to sugarcane bagasse alone, the xylo-oligosaccharide (degree of polymerization 2–5) yield from the acetyl-assisted autohydrolysis at 200 °C for 10 min was 52.99%. In addition, the yield of glucose from the solid residue following autohydrolysis pretreatment was 96.87% after 72 h of enzymatic hydrolysis. These results demonstrate that acetyl-assisted autohydrolysis is a promising method for the production of xylo-oligosaccharides.

Solid-state cultivation of recombinant Aspergillus nidulans to co-produce xylanase, arabinofuranosidase, and xylooligosaccharides from soybean fibre

Abstract Solid-state cultivations of genetically modified strains of Aspergillus nidulans A773, using soybean fibre as substrate, were carried out to produce xylanase and arabinofuranosidase, and these enzymes were subsequently used to obtain xylooligosaccharides using the same agro-residue. First, the best fungi cultivation conditions (moisture content, pH, temperature and addition of maltose) were optimized one-by-one for obtain the crude enzyme extracts. Subsequently, the application of xylanase on soybean fibre to obtain xylooligosaccharides was optimized by central composite design, defining best enzyme concentration and reaction temperature. The best condition obtained (50 °C and 117 U g−1 of soybean fibre) was used to evaluate the co-production of xylooligosaccharides by the addition of different concentrations of arabinofuranosidase. The highest yield of xylooligosaccharides obtained was 28% (mass fraction of xylan), showing final concentrations (in mg g−1 arabino-xylan) of 138.36 xylobiose (X2), 96.96 xylotriose (X3), and 53.04 xylotetraose (X4), in 9 h enzymatic reactions. The conversion of arabino-xylans into different xylooligosaccharides suggests the potential to use recombinant A. nidulans A773 enzymes to obtain prebiotics using a sugar-rich, low-cost soybean residue.

Biochemical characterization of a novel xylanase from Paenibacillus barengoltzii and its application in xylooligosaccharides production from corncobs

A novel xylanase gene (PbXyn10A) from Paenibacillus barengoltzii was cloned and expressed in Escherichia coli. PbXyn10A had an open reading frame of 3,063 bp, and its deduced amino acid sequence shared the highest identity of 72% with a xylanase from Paenibacillus curdlanolyticus. The recombinant xylanase (PbXyn10A) was purified and biochemically characterized. PbXyn10A was most active at pH 6.5 and 60 °C, respectively. It exhibited strict substrate specificity towards birchwood xylan, beechwood xylan and oat-spelt xylan, with Km values of 2.19, 2.04 and 2.51 mg/mL, respectively. The enzyme hydrolyzed xylan to yield mainly xylooligosaccharides (XOS) with degree of polymerization 2–4. A new strategy for XOS production from corncobs pretreated by steam explosion using acidic electrolyzed water, followed by enzymatic hydrolysis was developed. The highest XOS yield of 75% (based on xylan in raw corncobs) was achieved. This is the first report on a xylanase from Paenibacillus barengoltzii.