Browsing by Subject "HEMICELLULOSES"

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  • Razeq, Fakhria M.; Jurak, Edita; Stogios, Peter J.; Yan, Ruoyu; Tenkanen, Maija; Kabel, Mirjam A.; Wang, Weijun; Master, Emma R. (2018)
    Background: Acetylated 4-O-(methyl) glucuronoxylan (GX) is the main hemicellulose in deciduous hardwood, and comprises a beta-(1 -> 4)-linked xylopyranosyl (Xylp) backbone substituted by both acetyl groups and alpha-(1 -> 2)-linked 4-O-methylglucopyranosyluronic acid (MeGlcpA). Whereas enzymes that target singly acetylated Xylp or doubly 2,3-O-acetyl-Xylp have been well characterized, those targeting (2-O-MeGlcpA) 3-O-acetyl-Xylp structures in glucuronoxylan have remained elusive. Results: An unclassified carbohydrate esterase (FjoAcXE) was identified as a protein of unknown function from a polysaccharide utilization locus (PUL) otherwise comprising carbohydrate-active enzyme families known to target xylan. FjoAcXE was shown to efficiently release acetyl groups from internal (2-O-MeGlcpA) 3-O-acetyl-Xylp structures, an activity that has been sought after but lacking in known carbohydrate esterases. FjoAcXE action boosted the activity of alpha-glucuronidases from families GH67 and GH115 by five and nine times, respectively. Moreover, FjoAcXE activity was not only restricted to GX, but also deacetylated (3-O-Araf)2-O-acetyl-Xylp of feruloylated xylooligomers, confirming the broad substrate range of this new carbohydrate esterase. Conclusion: This study reports the discovery and characterization of the novel carbohydrate esterase, FjoAcXE. In addition to cleaving singly acetylated Xylp, and doubly 2,3-O-acetyl-Xylp, FjoAcXE efficiently cleaves internal 3-O-acetyl-Xylp linkages in (2-O-MeGlcpA)3-O-acetyl-Xylp residues along with densely substituted and branched xylooligomers; activities that until now were missing from the arsenal of enzymes required for xylan conversion.
  • Morais de Carvalho, Danila; Lahtinen, Maarit; Bhattarai, Mamata; Lawoko, Martin; Mikkonen, Kirsi S. (2021)
    Hemicellulose-rich wood extracts show efficient capacity to adsorb at emulsion interfaces and stabilize them. Their functionality is enhanced by lignin moieties accompanying the hemicellulose structures, in the form of lignin-carbohydrate complexes (LCCs) and, potentially, other non-covalent associations. The formation and stability of emulsions is determined by their interfacial regions. These are largely unexplored assemblies when formed from natural stabilizers with a complex chemical composition. Understanding the structure of the interfacial region could facilitate both designing the extraction processes of abundant biomasses and unraveling a valuable industrial application potential for the extracts. Herein, we characterized the LCCs from the interface of oil-in-water emulsions stabilized by galactoglucomannan (GGM) or glucuronoxylan (GX)-rich wood extracts, using two-dimensional nuclear magnetic resonance (NMR) spectroscopy analysis. The type of covalent linkage between residual lignin and hemicelluloses determined their partitioning between the continuous and interfacial emulsion phases. Benzylether structures, only found in the interface, were suggested to participate in the physical stabilization of the emulsion droplets. In turn, the phenylglycosides, preferentially observed in the continuous phase, were suggested to interact with adsorbed stabilizers by electrostatic interaction. More hydrophobic lignin structures, such as guaiacyl lignin type, dibenzodioxocin substructures, and certain end groups also contributed to droplet stabilization. The elucidation of such attributes is of paramount importance for the biorefinery industry, enabling the optimization of extraction processes for the preparation of wood-based stabilizers and designed interfaces for novel and sustainable emulsion systems.
  • Yilmaz-Turan, Secil; Jiménez-Quero, Amparo; Menzel, Carolin; Morais de Carvalho, Danila; Lindström, Mikael E.; Sevastyanova, Olena; Moriana, Rosana; Vilaplana, Francisco (2020)
    This study demonstrates the potential of feruloylated arabinoxylan (AX) from wheat bran for the preparation of bioactive barrier films with antioxidant properties. We have comprehensively evaluated the influence of the structural features and chemical acetylation of feruloylated AX extracted by subcritical water on their film properties, in comparison with alkaline extracted AX and a reference wheat endosperm AX. The degree of substitution (DS) of AX had a large influence on film formation, higher DS yielded better thermal and mechanical properties. The barrier properties of AX films were significantly enhanced by external plasticization by sorbitol. Chemical acetylation significantly improved the thermal stability but not the mechanical or barrier properties of the films. The presence of bound ferulic acid in feruloylated AX films resulted in higher antioxidant activity compared to external addition of free ferulic acid, which demonstrates their potential use in active packaging applications for the preservation of oxygen-sensitive foodstuff.
  • Valoppi, Fabio; Lahtinen, Maarit; Bhattarai, Mamata; Kirjoranta, Satu; Juntti, Venla; Peltonen, Leena; Kilpeläinen, Petri O.; Mikkonen, Kirsi S. (2019)
    With the emerging bio-based technologies, the fractionation of complex biomass is essential to obtain value-added functional molecules for material, chemical, and energy production. The refining process of biomasses often requires the use of solvents and hazardous chemicals, whose removal after fractionation decreases the eco-compatibility of the process and increases the cost and time of the refinement. Softwood extracts obtained through the environmentally friendly pressurized hot water extraction are heterogeneous mixtures rich in hemicelluloses and lignin. Here we developed a simple, fast, organic solvent-free, and sustainable method to fractionate softwood extracts using centrifugal forces. The characteristics of each obtained fraction in terms of composition, macromolecular properties (particle size, molar mass, charge), interfacial activity, and stabilization capacity were highly dependent on the centrifugal force and time applied. The hemicellulose and lignin contents in the fractions were balanced by centrifugal forces to obtain functional emulsifiers that efficiently stabilized the oil/water interface. Through fractionation of softwood extracts, we also found that both the hemicelluloses and lignin particles are involved in emulsion interface formation and stabilization. Centrifugation is a scalable concept that can be feasibly and easily introduced into the biorefinery system and used to optimize the composition of biomass fractions for targeted purposes.
  • Dilokpimol, Adiphol; Makela, Miia R.; Cerullo, Gabriella; Zhou, Miaomiao; Varriale, Simona; Gidijala, Loknath; Bras, Joana L. A.; Jutten, Peter; Piechot, Alexander; Verhaert, Raymond; Faraco, Vincenza; Hilden, Kristiina S.; de Vries, Ronald P. (2018)
    4-O-Methyl-D-glucuronic acid (MeGlcA) is a side-residue of glucuronoarabinoxylan and can form ester linkages to lignin, contributing significantly to the strength and rigidity of the plant cell wall. Glucuronoyl esterases (4-O-methyl-glucuronoyl methylesterases, GEs) can cleave this ester bond, and therefore may play a significant role as auxiliary enzymes in biomass saccharification for the production of biofuels and biochemicals. GEs belong to a relatively new family of carbohydrate esterases (CE15) in the CAZy database (www.cazy.org), and so far around ten fungal GEs have been characterized. To explore additional GE enzymes, we used a genome mining strategy. BLAST analysis with characterized GEs against approximately 250 publicly accessible fungal genomes identified more than 150 putative fungal GEs, which were classified into eight phylogenetic sub-groups. To validate the genome mining strategy, 21 selected GEs from both ascomycete and basidiomycete fungi were heterologously produced in Pichia pastoris. Of these enzymes, 18 were active against benzyl D-glucuronate demonstrating the suitability of our genome mining strategy for enzyme discovery.
  • Carvalho, Danila M.d.; Berglund, Jennie; Marchand, Célia; Lindström, Mikael E.; Vilaplana, Francisco; Sevastyanova, Olena (2019)
    The impact of various degrees of acetylation on improving the thermal stability of xylan isolated from different botanical source has been studied; methylglucuronoxylan from birch and eucalyptus, arabinoglucuronoxylan from spruce and glucuronoarabinoxylan from sugarcane bagasse and straw. The lower molecular weight of nonacetylated methylglucuronoxylan (17.7-23.7 kDa) and arabinoglucuronoxylan (16.8 kDa) meant that they were more soluble in water than glucuronoarabinoxylan (43.0-47.0 kDa). The temperature at the onset of degradation increased by 17-61 degrees C and by 75-145 degrees C for low and high acetylated xylans respectively, as a result of acetylation. A glass transition temperature in the range of 121-132 degrees C was observed for the samples non-acetylated and acetylated at low degree of acetylation (0.0-0.6). The acetylation to higher degrees (1.4-1.8) increased the glass transition temperature of the samples to 189-206 degrees C. Acetylation proved to be an efficient method for functionalization of the xylan to increase the thermal stability.
  • Giummarella, Nicola; Balakshin, Mikhail; Koutaniemi, Sanna; Karkonen, Anna; Lawoko, Martin (2019)
    The question of whether lignin is covalently linked to carbohydrates in native wood, forming what is referred to as lignin-carbohydrate complexes (LCCs), still lacks unequivocal proof. This is mainly due to the need to isolate lignin from woody materials prior to analysis, under conditions leading to partial chemical modification of the native wood polymers. Thus, the correlation between the structure of the isolated LCCs and LCCs in situ remains open. As a way to circumvent the problematic isolation, biomimicking lignin polymerization in vivo and in vitro is an interesting option. Herein, we report the detection of lignin-carbohydrate bonds in the extracellular lignin formed by tissue-cultured Norway spruce cells, and in modified biomimetic lignin synthesis (dehydrogenation polymers). Semi-quantitative 2D heteronuclear singular quantum coherence (HSQC)-, P-31 -, and C-13-NMR spectroscopy were applied as analytical tools. Combining results from these systems, four types of lignin-carbohydrate bonds were detected; benzyl ether, benzyl ester, gamma-ester, and phenyl glycoside linkages, providing direct evidence of lignin-carbohydrate bond formation in biomimicked lignin polymerization. Based on our findings, we propose a sequence for lignin-carbohydrate bond formation in plant cell walls.
  • Hyväkkö, Uula; Maltari, Riku; Kakko, Tia; Kontro, Jussi; Mikkilä, Joona; Kilpeläinen, Petri; Enqvist, Eric; Tikka, Panu; Hilden, Kristiina; Nousiainen, Paula; Sipilä, Jussi (2020)
    In modern biorefineries, low value lignin and hemicellulose fractions are produced as side streams. New extraction methods for their purification are needed in order to utilize the whole biomass more efficiently and to produce special target products. In several new applications using plant based biomaterials, the native-type chemical and polymeric properties are desired. Especially, production of high-quality native-type lignin enables valorization of biomass entirely, thus making novel processes sustainable and economically viable. To investigate sulfur-free possibilities for so-called "lignin first" technologies, we compared alkaline organosolv, formic acid organosolv, and ionic liquid processes to simple soda "cooking" using wheat straw and aspen as raw materials. All experiments were carried out using microwave-assisted pulping approach toy enable rapid heat transfer and convenient control of temperature and pressure. The main target was to evaluate the advantage of a brief hot water extraction as a pretreatment for the pulping process. Most of these novel pulping methods resulted in high-quality lignin, which may be valorized more diversely than kraft lignin. Lignin fractions were thoroughly analyzed with NMR (C-13 and HSQC) and gel permeation chromatography to study the quality of the collected lignin. The cellulose fractions were analyzed by determining their lignin contents and carbohydrate profiles for further utilization in cellulose-based products or biofuels.