Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.635
Filtrar
1.
Environ Res ; 216(Pt 2): 114400, 2023 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-36265604

RESUMO

Biowaste, produced from nature, is preferred to be a good source of carbon and ligninolytic machinery for many microorganisms. They are complex biopolymers composed of lignin, cellulose, and hemicellulose traces. This biomass can be depolymerized to its nano-dimensions to gain exceptional properties useful in the field of cosmetics, pharmaceuticals, high-strength materials, etc. Nano-sized biomass derivatives overcome the inherent drawbacks of the parent material and offer promises as a potential material for a wide range of applications with their unique traits such as low-toxicity, biocompatibility, biodegradability and environmentally friendly nature with versatility. This review focuses on the production of value-added products feasible from nanocellulose, nano lignin, and xylan nanoparticles which is quite a novel study of its kind. Dawn of nanotechnology has converted bio waste by-products (hemicellulose and lignin) into useful precursors for many commercial products. Nano-cellulose has been employed in the fields of electronics, cosmetics, drug delivery, scaffolds, fillers, packaging, and engineering structures. Xylan nanoparticles and nano lignin have numerous applications as stabilizers, additives, textiles, adhesives, emulsifiers, and prodrugs for many polyphenols with an encapsulation efficiency of 50%. This study will support the potential development of composites for emerging applications in all aspects of interest and open up novel paths for multifunctional biomaterials in nano-dimensions for cosmetic, drug carrier, and clinical applications.


Assuntos
Lignina , Xilanos , Lignina/química , Celulose/química , Biomassa
2.
Carbohydr Polym ; 301(Pt A): 120292, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36436850

RESUMO

In order to explore the contributions of hemicelluloses to the assembly and mechanical properties of cellulose networks, the bacterial cellulose (BC) composites containing xylan and glucomannan were prepared to mimic the polysaccharides network of plant cell walls. Both polysaccharides could induce the change of diameters of cellulose ribbons and influence the crystallization of cellulose. Besides, small-angle X-ray scattering (SAXS) demonstrated that xylan inhibited the assembly of microfibrils into cellulose ribbons, while glucomannan promoted the packing of microfibrils. The changes of cellulose crystalline structure and assembly pattern of cellulose contributed to the lower tensile strength and higher strain at break of the BC composites as compared with the BC. The results provide a profound insight into the structure-property relationships of cellulose networks affected by hemicelluloses, which could be conducive to the development of cellulose biomaterials.


Assuntos
Celulose , Xilanos , Celulose/química , Xilanos/química , Espalhamento a Baixo Ângulo , Difração de Raios X , Polissacarídeos/química , Bactérias/química
3.
Carbohydr Polym ; 301(Pt A): 120305, 2023 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-36436868

RESUMO

To elucidate the influence of polysaccharides on hardwood lignification, dehydrogenative polymerization of monolignols, coniferyl alcohol (CA) and sinapyl alcohol (SA), was attempted with recombinant cationic cell wall-bound peroxidase (rCWPO-C) and horseradish peroxidase (HRP) in measurement cells of a quartz crystal microbalance with dissipation (QCM-D). Hardwood cellulose nanofibers were anchored; hemicelluloses, xylan, partially acetylated xylan (AcXY), galactoglucomannan, and xyloglucan, and the enzymes were subsequently adsorbed onto the QCM-D sensor surface, enabling fabrication of artificial polysaccharide matrices. The largest amount of rCWPO-C is found to be adsorbed onto AcXY among all the polysaccharides, which affords the largest amount and size of spherical dehydrogenation polymers (DHPs) from both CA and SA. In contrast, no DHP and a small amount of DHPs are formed from SA and CA, respectively, by HRP catalysis in all of the polysaccharide matrices. This study demonstrates important functions of a real tree-derived peroxidase, rCWPO-C, and AcXY for hardwood lignification.


Assuntos
Peroxidase , Xilanos , Polimerização , Xilanos/química , Lignina/química , Peroxidases , Parede Celular/química , Peroxidase do Rábano Silvestre/metabolismo , Polímeros/química
4.
Food Chem ; 404(Pt B): 134687, 2023 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-36323030

RESUMO

Oat (Avena sativa) is a nutritionally important cereal crop that is rich in health-promoting dietary fibers, favorable proteins and polar lipids. In this work, ca. 500 random lines of a mutagenized oat population of high genetic variation were screened for arabinoxylan (AX) content. This identified lines with up to 60% higher AX levels in flour from whole seed and up to 100% higher in flour from dehulled seeds, as compared to the original Belinda variety. In addition, the cellular localization of AX was determined in cross-sections of dehulled seeds from three high and one low AX line using a xylan-specific antibody. This revealed variations in the amount and localization of AX between high and low AX lines. The high AX lines will now serve as a starting point in the development of oat varieties with superior health-promoting and rheological properties.


Assuntos
Avena , Xilanos , Xilanos/metabolismo , Avena/genética , Avena/metabolismo , Farinha/análise , Grão Comestível/metabolismo
5.
Carbohydr Polym ; 300: 120245, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36372479

RESUMO

Selective dissolution of industrial biowaste is of significant importance for the valorization of biomass. Especially, fractionation of polysaccharides with similar structures is more challenging. Herein, a new kind of cationic hydrotrope, tetraethylammonium hydroxide (TEAH), has been developed for rapid, efficient, and selective dissolution of industrial biowastes-xylan type hemicelluloses from viscose fiber mills. When the concentration of TEAH is 15 wt%, the solubility of industrial crystalline xylan reaches to 13.39 wt% at room temperature. Crystalline or amorphous xylan can be regenerated by adding water or ethanol, with 57.98 % and 95.45 % yields, respectively. Additionally, we showcase hemicelluloses were near-completely extracted from holocellulose without degrading cellulose under ambient temperature by simply adjusting the concentration of TEAH, demonstrating the advantage of the hydrotropic feature. This hydrotrope solvent system features selective, rapid, and room temperature dissolution polysaccharides, which will shed new light in technological applications of the industrial spinning or biorefining processes.


Assuntos
Polissacarídeos , Xilanos , Solubilidade , Temperatura , Polissacarídeos/química
6.
Carbohydr Polym ; 300: 120251, 2023 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-36372482

RESUMO

A modular synthesis was developed to obtain reactive xylan derivatives that are accessible for further functionalization and chemical crosslinking by click-chemistry approaches. Xylan phenylcarbonates (XPCs) with degrees of substitution (DS) from 0.62 to 1.94 were converted with propargyl amine (PA) or 6-azidohexan-1-amine (AA) to introduce either alkynyl- or azido moieties into the polymer backbone. Quantitative conversion of the XPC derivatives into functional xylan carbamates (XCs) with well-defined DS values was achieved. The molecular structure of the compounds was confirmed by FTIR- and NMR spectroscopy. Covalent crosslinking of alkynyl-functionalized XCs with bisazide linkers was achieved by copper-catalyzed 1,3-dipolar cycloaddition in an organic medium and the gelation process was studied by rheological experiments. Finally, it was demonstrated that mixed XCs with a reactive moiety and another functional group, which induce water solubility, are accessible. The corresponding products are suitable for the preparation of xylan-based hydrogels.


Assuntos
Alcinos , Xilanos , Alcinos/química , Química Click , Reação de Cicloadição , Aminas , Azidas/química
7.
Sci Total Environ ; 857(Pt 2): 159442, 2023 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-36252666

RESUMO

This study investigated the potential of ensiling pretreatment fortified with laccase and a lactic acid bacteria (LAB) inoculant on improving the utilization of alfalfa stems for bioethanol production. The alfalfa stems were ensiled with no additives (Con), 0.04 % laccase (LA), a LAB inoculant containing Pediococcus pentosaceus at 1 × 106 fresh weight (FW) and Pediococcus acidilactici at 3 × 105 cfu/g FW (PP), and a combination of LA and PP (LAP) for 120 days. By reshaping the bacterial community structure of alfalfa stem silages toward a higher abundance of Lactobacillus, the addition of laccase and LAB inoculant either alone or in combination facilitated lactic acid fermentation to reduce fermentation losses, as evidenced by low concentrations of ammonia nitrogen (53.7 to 68.9 g/kg total nitrogen) and ethanol (2.63 to 3.55 g/kg dry matter). All additive treatments increased lignocellulose degradation and soluble sugars concentrations of alfalfa stem silages. Due to delignification and polyphenol removal, glucan and xylan conversion (70.3 % vs. 35.7 % and 51.6 % vs. 27.9 %, respectively) and ethanol conversion efficiency (53.9 % vs. 26.4 %) of alfalfa stems were greatly increased by ensiling fortified with LA versus Con, and these variables (79.8 % for glucan, 58.7 % for xylan, and 60.1 % for ethanol conversion efficiency) were further enhanced with a synergistic effect of LA and PP fortification. The spearman correlation analysis revealed that bioethanol fermentation of silage biomass was closely related to ensiling parameters and total phenols. In conclusion, ensiling pretreatment with LA and PP combination offered a feasible way to efficient utilization of alfalfa stems for bioethanol production.


Assuntos
Inoculantes Agrícolas , Medicago sativa , Medicago sativa/metabolismo , Inoculantes Agrícolas/metabolismo , Lacase/metabolismo , Biomassa , Xilanos , Silagem/análise , Silagem/microbiologia , Fermentação , Ácido Láctico/metabolismo , Etanol/análise , Nitrogênio , Glucanos/metabolismo
8.
Food Res Int ; 162(Pt A): 112019, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36461305

RESUMO

Xylo-oligosaccharides (XOS) are emerging prebiotics that have recently been gained a great interest in the market of functional foods. Since their beneficial activity strictly depends on their chemical structure and on their degree of polymerization (DP), in this work an enzymatic method was developed to produce XOS with variable and modellable DPs, involving a combination of a commercial endo-ß-1,4-xylanase M3 from Trichoderma longibrachiatum and a deacetylase, using a commercial acetylated standard xylan as substrate. A Design of Experiment (DoE) was developed and through the variation of some hydrolysis conditions, some experiments allowed to obtain significant amounts of XOS with DP 7-10, up to 11%, despite XOS with DP 2-4 were always the most abundant (60-96% of total XOS). The most impacting parameter on the XOS distribution was the order of addition of the xylanase and deacetylating enzyme, while pH showed to have a great influence on the total yield. The method was also tested on an acetylated xylan extracted from grape stalks, structurally similar to the commercial standard xylan. The model was found to work in a very similar way also on the non-purified xylan sample, allowing the manipulation of enzymatic hydrolysis on a low-cost by-product, with the potential to obtain on a large scale XOS with high added value and with a specific DP, depending on the final application.


Assuntos
Oligossacarídeos , Xilanos , Hidrólise , Polimerização , Prebióticos
9.
Poult Sci ; 101(12): 102210, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36334432

RESUMO

This study evaluated the impact of feeding xylo-oligosaccharides (XOS), fermentable fiber in the form of wheat bran (WB), and xylanase (XYL) on laying hen productive performance and nutrient digestibility. The hypothesis was that the WB would provide the microbiota in the hindgut with fermentable dietary xylan, and the XOS and XYL would further upregulate xylan fermentation pathways, resulting in improved nutrient utilization. Isa Brown hens (n = 96) were obtained at 39 wk of age. They were fed 12 dietary treatments, 8 hens per treatment, for 56 d. A commercial laying hen ration was fed, and for half of the treatments 10% of this ration was directly replaced with WB. The diets were then supplemented with either 1) no supplements; 2) XOS 50 g/t; 3) XOS 2000 g/t; 4) XYL (16,000 BXU/kg); 5) XYL + XOS 50 g/t, or 6) XYL + XOS 2,000 g/t. Hen performance and egg quality were measured every 14 d. On d56, ileum digesta samples were collected for determination of starch, nonstarch polysaccharide (NSP), XOS, protein, energy, and starch digestibility. Ceca digesta samples were also collected for analysis of XOS, short chain fatty acid (SCFA), xylanase and cellulase activity and microbial counts. Feeding 2,000 g/t XOS increased ileal protein digestibility. Combined 2,000 g/t XOS and XYL increased cecal Bifidobacteria concentration. This combination also increased cecal xylanase activity in birds fed the control diet. Cecal cellulase activity was improved by feeding WB, XYL, and 2,000 g/t XOS. XYL increased cecal lactate production. Feeding 2,000 g/t XOS with WB increased insoluble NSP degradability and shell breaking strength at d56. In summary, supplementing laying hen diets with fermentable fiber, XYL and XOS increases utilization of dietary xylan, improving nutrient utilization, performance, and gastrointestinal health.


Assuntos
Celulases , Galinhas , Animais , Feminino , Galinhas/fisiologia , Fenômenos Fisiológicos da Nutrição Animal , Ração Animal/análise , Xilanos/metabolismo , Dieta/veterinária , Oligossacarídeos/metabolismo , Suplementos Nutricionais/análise , Fibras na Dieta/metabolismo , Nutrientes , Polissacarídeos/metabolismo , Amido/metabolismo , Celulases/metabolismo , Digestão
10.
Int J Mol Sci ; 23(22)2022 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-36430284

RESUMO

Fungal arabinofuranosidases (ABFs) catalyze the hydrolysis of arabinosyl substituents (Ara) and are key in the interplay with other glycosyl hydrolases to saccharify arabinoxylans (AXs). Most characterized ABFs belong to GH51 and GH62 and are known to hydrolyze the linkage of α-(1→2)-Ara and α-(1→3)-Ara in monosubstituted xylosyl residues (Xyl) (ABF-m2,3). Nevertheless, in AX a substantial number of Xyls have two Aras (i.e., disubstituted), which are unaffected by ABFs from GH51 and GH62. To date, only two fungal enzymes have been identified (in GH43_36) that specifically release the α-(1→3)-Ara from disubstituted Xyls (ABF-d3). In our research, phylogenetic analysis of available GH43_36 sequences revealed two major clades (GH43_36a and GH43_36b) with an expected substrate specificity difference. The characterized fungal ABF-d3 enzymes aligned with GH43_36a, including the GH43_36 from Humicola insolens (HiABF43_36a). Hereto, the first fungal GH43_36b (from Talaromyces pinophilus) was cloned, purified, and characterized (TpABF43_36b). Surprisingly, TpABF43_36b was found to be active as ABF-m2,3, albeit with a relatively low rate compared to other ABFs tested, and showed minor xylanase activity. Novel specificities were also discovered for the HiABF43_36a, as it also released α-(1→2)-Ara from a disubstitution on the non-reducing end of an arabinoxylooligosaccharide (AXOS), and it was active to a lesser extent as an ABF-m2,3 towards AXOS when the Ara was on the second xylosyl from the non-reducing end. In essence, this work adds new insights into the biorefinery of agricultural residues.


Assuntos
Triticum , Xilanos , Filogenia , Xilanos/química
11.
Int J Mol Sci ; 23(21)2022 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-36362138

RESUMO

Xylooligosaccharides (XOS) are widely used in the food industry as prebiotic components. XOS with high purity are required for practical prebiotic function and other biological benefits, such as antioxidant and inflammatory properties. In this work, we immobilized the recombinant endo-1,4-ß-xylanase of Malbranchea pulchella (MpXyn10) in various chemical supports and evaluated its potential to produce xylooligosaccharides (XOS) from hydrothermal liquor of eucalyptus wood chips. Values >90% of immobilization yields were achieved from amino-activated supports for 120 min. The highest recovery values were found on Purolite (142%) and MANAE-MpXyn10 (137%) derivatives, which maintained more than 90% residual activity for 24 h at 70 °C, while the free-MpXyn10 maintained only 11%. In addition, active MpXyn10 derivatives were stable in the range of pH 4.0-6.0 and the presence of the furfural and HMF compounds. MpXyn10 derivatives were tested to produce XOS from xylan of various sources. Maximum values were observed for birchwood xylan at 8.6 mg mL-1 and wheat arabinoxylan at 8.9 mg mL-1, using Purolite-MpXyn10. Its derivative was also successfully applied in the hydrolysis of soluble xylan present in hydrothermal liquor, with 0.9 mg mL-1 of XOS after 3 h at 50 °C. This derivative maintained more than 80% XOS yield after six cycles of the assay. The results obtained provide a basis for the application of immobilized MpXyn10 to produce XOS with high purity and other high-value-added products in the lignocellulosic biorefinery field.


Assuntos
Eucalyptus , Xilanos , Madeira , Glucuronatos , Oligossacarídeos/química , Endo-1,4-beta-Xilanases , Prebióticos , Hidrólise
12.
Appl Environ Microbiol ; 88(21): e0130222, 2022 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-36218355

RESUMO

Caldicellulosiruptor species scavenge carbohydrates from runoff containing plant biomass that enters hot springs and from grasses that grow in more moderate parts of thermal features. While only a few Caldicellulosiruptor species can degrade cellulose, all known species are hemicellulolytic. The most well-characterized species, Caldicellulosiruptor bescii, decentralizes its hemicellulase inventory across five different genomic loci and two isolated genes. Transcriptomic analyses, comparative genomics, and enzymatic characterization were utilized to assign functional roles and determine the relative importance of its six putative endoxylanases (five glycoside hydrolase family 10 [GH10] enzymes and one GH11 enzyme) and two putative exoxylanases (one GH39 and one GH3) in C. bescii. Two genus-wide conserved xylanases, C. bescii XynA (GH10) and C. bescii Xyl3A (GH3), had the highest levels of sugar release on oat spelt xylan, were in the top 10% of all genes transcribed by C. bescii, and were highly induced on xylan compared to cellulose. This indicates that a minimal set of enzymes are used to drive xylan degradation in the genus Caldicellulosiruptor, complemented by hemicellulolytic inventories that are tuned to specific forms of hemicellulose in available plant biomasses. To this point, synergism studies revealed that the pairing of specific GH family proteins (GH3, -11, and -39) with C. bescii GH10 proteins released more sugar in vitro than mixtures containing five different GH10 proteins. Overall, this work demonstrates the essential requirements for Caldicellulosiruptor to degrade various forms of xylan and the differences in species genomic inventories that are tuned for survival in unique biotopes with variable lignocellulosic substrates. IMPORTANCE Microbial deconstruction of lignocellulose for the production of biofuels and chemicals requires the hydrolysis of heterogeneous hemicelluloses to access the microcrystalline cellulose portion. This work extends previous in vivo and in vitro efforts to characterize hemicellulose utilization by integrating genomic reconstruction, transcriptomic data, operon structures, and biochemical characteristics of key enzymes to understand the deployment and functionality of hemicellulases by the extreme thermophile Caldicellulosiruptor bescii. Furthermore, comparative genomics of the genus revealed both conserved and divergent mechanisms for hemicellulose utilization across the 15 sequenced species, thereby paving the way to connecting functional enzyme characterization with metabolic engineering efforts to enhance lignocellulose conversion.


Assuntos
Regulon , Xilanos , Celulose/metabolismo , Clostridiales/metabolismo , Açúcares
13.
Int J Biol Macromol ; 222(Pt B): 1876-1887, 2022 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-36202332

RESUMO

The complex interaction of lignin, cellulose, and hemicellulose in the hydrothermal degradation progress of lignocellulose, has led to uncertainty in the hydrothermal synthesis of lignocellulose-based CQDs (LC-CQDs). This makes it difficult to identify the specific formation mechanism of LC-CQDs. To simplify the reaction system and comprehensively describe the formation of LC-CQDs, both lignin and hemicellulose, the main hydrothermal degradation products of lignocellulose, were used as precursor to simulate and explore the synthesis of LC-CQDs at different time intervals (2-12 h). First, different lignin models were employed for preparing CQDs to determine the key lignin structure that govern CQDs formation. G-type lignin-model based CQDs were shown to have higher fluorescence intensity than H- and S-type. Then, G-type lignin model and hemicellulose model (xylan) were used simultaneously hydrothermal to prepare LC-CQDs. The analysis shows that the carbon nucleus preferentially formed by the lignin provides growth sites for small molecules degraded from hemicellulose, which gradually grow around the carbon core over time, thus forming a "sunflower" structure of CQDs. The presence of a lignin model could effectively guide the small molecules toward CQDs formation instead of carbonization. Additionally, the CQDs exhibit good in-vivo imaging performance.


Assuntos
Pontos Quânticos , Pontos Quânticos/química , Carbono/química , Lignina/química , Xilanos
14.
J Agric Food Chem ; 70(41): 13349-13357, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36205442

RESUMO

Corn bran is an abundant coprocessing stream of corn-starch processing, rich in highly substituted, diferuloyl-cross-linked glucurono-arabinoxylan. The diferuloyl cross-links make the glucurono-arabinoxylan recalcitrant to enzymatic conversion and constitute a hindrance for designing selective enzymatic upgrading of corn glucurono-arabinoxylan. Here, we show that two bacterial feruloyl esterases, wtsFae1A and wtsFae1B, each having a carbohydrate-binding module of family 48, are capable of cleaving the ester bonds of the cross-linkages and releasing 5-5', 8-5', 8-5' benzofuran, and 8-O-4' diferulate from soluble and insoluble corn bran glucurono-arabinoxylan. All four diferulic acids were released at similar efficiency, indicating nondiscriminatory enzymatic selectivity for the esterified dimer linkages, the only exception being that wtsFae1B had a surprisingly high propensity for releasing the dimers, especially 8-5' benzofuran diferulate, indicating a potential, unique catalytic selectivity. The data provide evidence of direct enzymatic release of diferulic acids from corn bran by newly discovered feruloyl esterases, i.e., a new enzyme activity. The findings yield new insight and create new opportunities for enzymatic opening of diferuloyl cross-linkages to pave the way for upgrading of recalcitrant arabinoxylans.


Assuntos
Benzofuranos , Zea mays , Zea mays/química , Hidrolases de Éster Carboxílico/química , Xilanos/química , Ácidos Cumáricos/química , Fibras na Dieta , Ésteres , Amido , Esterases
15.
Sci Rep ; 12(1): 17219, 2022 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-36241677

RESUMO

The production of second-generation fuels from lignocellulosic residues such as sugarcane bagasse (SCB) requires the synergistic interaction of key cellulose-degrading enzymes and accessory proteins for their complete deconstruction to useful monomeric sugars. Here, we recombinantly expressed and characterized unknown GH5 xylanase from P. funiculosum (PfXyn5) in Pichia pastoris, which was earlier found in our study to be highly implicated in SCB saccharification. The PfXyn5 has a molecular mass of ~ 55 kDa and showed broad activity against a range of substrates like xylan, xyloglucan, laminarin and p-nitrophenyl-ß-D-xylopyranoside, with the highest specific activity of 0.7 U/mg against xylan at pH 4.5 and 50 °C. Analysis of the degradation products of xylan and SCB by PfXyn5 showed significant production of xylooligosaccharides (XOS) with a degree of polymerization (DP) ranging from two (DP2) to six (DP6), thus, suggesting that the PfXyn5 is an endo-acting enzyme. The enzyme synergistically improved the saccharification of SCB when combined with the crude cellulase cocktail of P. funiculosum with a degree of synergism up to 1.32. The PfXyn5 was further expressed individually and simultaneously with a notable GH16 endoglucanase (PfEgl16) in a catabolite-derepressed strain of P. funiculosum, PfMig188, and the saccharification efficiency of the secretomes from the resulting transformants were investigated on SCB. The secretome of PfMig188 overexpressing Xyn5 or Egl16 increased the saccharification of SCB by 9% or 7%, respectively, over the secretome of PfMig188, while the secretome of dual transformant increased SCB saccharification by ~ 15% at the same minimal protein concentration.


Assuntos
Celulase , Saccharum , Celulase/metabolismo , Celulose/química , Endo-1,4-beta-Xilanases/química , Hidrólise , Saccharum/metabolismo , Açúcares/metabolismo , Talaromyces , Xilanos/metabolismo
16.
Int J Mol Sci ; 23(19)2022 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-36233128

RESUMO

Hydrothermal pretreatment (HTP) has long been considered as an efficient and green treatment process on lignocellulosic biomass for bioconversion. However, the variations of cellulose supramolecular structures during HTP as well as their effects on subsequent enzymatic conversion are less understood. In this work, bamboo holocellulose with well-connected cellulose and hemicelluloses polysaccharides were hydrothermally treated under various temperatures. Chemical, morphological, and crystal structural determinations were performed systematically by a series of advanced characterizations. Xylan was degraded to xylooligosaccharides in the hydrolyzates accompanied by the reduced degree of polymerization for cellulose. Cellulose crystallites were found to swell anisotropically, despite the limited decrystallization by HTP. Hydrogen bond linkages between cellulose molecular chains were weakened due to above chemical and crystal variations, which therefore swelled, loosened, and separated the condensed cellulose microfibrils. Samples after HTP present notably increased surface area, favoring the adsorption and subsequent hydrolysis by cellulase enzymes. A satisfying enzymatic conversion yield (>85%) at rather low cellulase enzyme dosage (10 FPU/g glucan) was obtained, which would indicate new understandings on the green and efficient bioconversion process on lignocellulosic biomass.


Assuntos
Celulase , Lignina , Celulase/metabolismo , Celulose/química , Hidrólise , Lignina/metabolismo , Polissacarídeos/metabolismo , Xilanos
17.
Int J Mol Sci ; 23(19)2022 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-36233140

RESUMO

Xyloglucan endotransglycosylases (XETs) play key roles in the remodelling and reconstruction of plant cell walls. These enzymes catalyse homo-transglycosylation reactions with xyloglucan-derived donor and acceptor substrates and hetero-transglycosylation reactions with a variety of structurally diverse polysaccharides. In this work, we describe the basis of acceptor substrate binding specificity in non-specific Tropaeolum majus (TmXET6.3) and specific Populus tremula x tremuloides (PttXET16A) XETs, using molecular docking and molecular dynamics (MD) simulations combined with binding free energy calculations. The data indicate that the enzyme-donor (xyloglucan heptaoligosaccharide or XG-OS7)/acceptor complexes with the linear acceptors, where a backbone consisted of glucose (Glc) moieties linked via (1,4)- or (1,3)-ß-glycosidic linkages, were bound stably in the active sites of TmXET6.3 and PttXET16A. Conversely, the acceptors with the (1,6)-ß-linked Glc moieties were bound stably in TmXET6.3 but not in PttXET16A. When in the (1,4)-ß-linked Glc containing acceptors, the saccharide moieties were replaced with mannose or xylose, they bound stably in TmXET6.3 but lacked stability in PttXET16A. MD simulations of the XET-donor/acceptor complexes with acceptors derived from (1,4;1,3)-ß-glucans highlighted the importance of (1,3)-ß-glycosidic linkages and side chain positions in the acceptor substrates. Our findings explain the differences in acceptor binding specificity between non-specific and specific XETs and associate theoretical to experimental data.


Assuntos
Química Computacional , beta-Glucanas , Glucose , Glicosilação , Glicosiltransferases/metabolismo , Manose , Simulação de Acoplamento Molecular , Plantas/metabolismo , Polissacarídeos/metabolismo , Especificidade por Substrato , Xilanos/química , Xilose
18.
Carbohydr Polym ; 298: 120023, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36241256

RESUMO

Polysaccharides are important constituents in Dolichos lablab hull. Herein, pectin-glucuronoxylan complex from D. lablab hull designated as DLHP-3 (D. lablab hull polysaccharide,) was prepared by ion exchange and gel permeation chromatography, and further characterized by acid degradation and enzymatic hydrolysis, methylation combined with GC-MS, NMR and MALDI-TOF-MS analysis. Both of pectin and glucuronoxylan regions were found in DLHP-3. The glucuronoxylan region consisted of a →4)-ß-Xylp-(1→ backbone with branches of α-GlcpA-(1→ substituted at O-2 site, and the ratio of xylose to glucuronic acid was about 5:1. Acetyl groups were mainly attached to O-3 site of →2,4)-ß-Xylp-(1→ residues. The main chain of pectin region could be represented by →4)-α-GalpA-(1→4)-α-GalpA-(1→ and →2)-α-Rhap-(1→4)-α-GalpA-(1→ with partial methyl-esterification. The side chains were deduced to embrace arabinan and arabinogalactan linked to rhamnogalacturonan-I region. Pectin was probably covalently bound to glucuronoxylan. Our findings uncovered the molecular structure of pectin-glucuronoxylan complex from D. lablab hull.


Assuntos
Dolichos , Dolichos/metabolismo , Ácido Glucurônico , Pectinas/química , Polissacarídeos/química , Ramnogalacturonanos , Xilanos , Xilose
19.
Carbohydr Polym ; 298: 120097, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36241278

RESUMO

Biorefinery with deep eutectic solvent (DES) is an emerging processing technology to overcome the shortcomings of conventional biomass pretreatments. This work evaluates the biorefinery of sugarcane bagasse (SCB) with DES formulated with choline chloride as hydrogen bond acceptor and three hydrogen bond donors: lactic acid, citric acid, and acetic acid. Acetic acid showed unique ionic properties responsible for the selective removal of lignin and the deconstruction of cellulose to improve the digestibility of up to 97.61 % of glucan and 63.95 % of xylan during enzymatic hydrolysis. In addition, the structural characteristics of the polysaccharide-rich material (PRM) were analyzed by X-rays, ATR-FTIR, SEM, and enzymatic hydrolysis, and compared with the original material sample, for a comprehensive understanding of biomass deconstruction using different hydrogen bond donors (HBD) as DES pretreatment.


Assuntos
Lignina , Saccharum , Ácido Acético , Biomassa , Celulose/química , Colina/química , Ácido Cítrico , Solventes Eutéticos Profundos , Grão Comestível , Glucanos , Hidrólise , Ácido Láctico , Lignina/química , Polissacarídeos , Solventes/química , Xilanos
20.
J Org Chem ; 87(21): 14544-14554, 2022 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-36251002

RESUMO

It was recently demonstrated by us that acetyl groups in oligosaccharides can migrate not only within one saccharide unit but also between two different saccharide units. Kinetics of this phenomenon were previously investigated in both mannan model compounds and a naturally occurring polysaccharide. In addition to mannans, there are also several other naturally acetylated polysaccharides, such as xyloglucans and xylans. Both xyloglucans and xylans are some of the most common acetylated polysaccharides in nature, displaying important roles in the plant cells. Considering the various biological roles of natural polysaccharides, it could be hypothesized that the intramolecular migration of acetyl groups might also be associated with regulation of the biological activity of polysaccharides in nature. Consequently, a better understanding of the overall migration phenomenon across the glycosidic bonds could help to understand the potential role of such migrations in the context of the biological activity of polysaccharides. Here, we present a detailed investigation on acetyl group migration in the synthesized xylan and glucan trisaccharide model compounds by a combination of experimental and computational methods, showing that the migration between the saccharide units proceeds from a secondary hydroxyl group of one saccharide unit toward a primary hydroxyl group of the other unit.


Assuntos
Glucanos , Xilanos , Xilanos/química , Polissacarídeos/química , Oligossacarídeos/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...