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|Stability:||> 10 years under recommended storage conditions|
|Viscosity:||> 10 dL/g|
|Monosaccharides (%):||Galactose : mannose = 21: 79|
|Main Chain Glycosidic Linkage:||β-1,4 and α-1,6|
|Substrate For (Enzyme):||endo-1,4-β-Mannanase|
High purity Galactomannan (Carob; High Viscosity) for use in research, biochemical enzyme assays and in vitro diagnostic analysis.
For viscometric assays.
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Mallett, I., McCleary, B. V. & Matheson, N. K. (1987). Phytochemistry, 26(7), 1889-1894.
Galactomannan has been extracted from the endosperm of seeds of Gleditsia triacanthos (honey locust) at different stages of development, when the seed was accumulating storage material. Properties of the different samples have been studied. The molecular size distribution became more disperse as galactomannan accumulated and the galactose: mannose ratio decreased slightly. Some possible reasons for these changes are discussed.Hide Abstract
Dea, I. C. M., Clark, A. H. & McCleary, B. V. (1986). Carbohydrate Research, 147(2), 275-294.
A range of galactomannans varying widely in the contents of D-galactose have been compared for self-association and their interaction properties with agarose and xanthan. Whereas, in general, the most interactive galactomannans are those in which the (1→4)-β-D-mannan chain is least substituted by α-D-galactosyl stubs, evidence is presented which indicates that the distribution of D-galactosyl groups along the backbone (fine structure) can have a significant effect on the interaction properties. For galactomannans containing <30% of D-galactose, those which contain a higher frequency of unsubstituted blocks of intermediate length in the β-D-mannan chain are most interactive. For galactomannans containing >40% of D-galactose, those which contain a higher frequency of exactly alternating regions in the β-D-mannan chain are most interactive. This selectivity, on the basis of galactomannan fine-structure, in mixed polysaccharide interactions in vitro could mimic the selectivity of binding of branched plant-cell-wall polysaccharides in biological systems.Hide Abstract
Effect of the molecular fine structure of galactomannans on their interaction properties - the role of unsubstituted sides.
Dea, I. C. M., Clark, A. H. & McCleary, B. V. (1986). Food Hydrocolloids, 1(2), 129-140.
A range of galactomannans varying widely in the content of D-galactose have been compared for self-association, and their interaction properties with agarose and xanthan. The results presented indicate that in general the most interactive galactomannans are those in which the D-mannan main chain bears fewest D-galactose stubs, and confirm that the distribution of D-galactose groups along the main chain can have a significant effect on the interactive properties of the galactomannans. It has been shown that freeze — thaw precipitation of galactomannans requires regions of totally unsubstituted D-mannose residues along the main chain, and that a threshold for significant freeze — thaw precipitation occurs at a weight-average length of totally unsubstituted residues of approximately six. For galactomannans having structures above this threshold their interactive properties with other polysaccharides are controlled by structural features associated with totally unsubstituted regions of the D-mannan backbone. In contrast, for galactomannans below this threshold, their interactive properties are controlled by structural features associated with unsubstituted sides of D-mannan backbone.
McCleary, B. V., Clark, A. H., Dea, I. C. M. & Rees, D. A. (1985). Carbohydrate Research, 139, 237-260.
The distribution of D-galactosyl groups along the D-mannan backbone (fine structure) of carob and guar galactomannans has been studied by a computer analysis of the amounts and structures of oligosaccharides released on hydrolysis of the polymers with two highly purified β-D-mannanases isolated from germinated guar seed and from Aspergillus niger cultures. Computer programmes were developed which accounted for the specific subsite-binding requirements of the β-D-mannanases and which simulated the synthesis of galactomannan by processes in which the D-galactosyl groups were transferred to the growing D-mannan chain in either a statistically random manner or as influenced by nearest-neighbour/second-nearest-neighbour substitution. Such a model was chosen as it is consistent with the known pattern of synthesis of similar polysaccharides, for example, xyloglucan; also, addition to a preformed mannan chain would be unlikely, due to the insoluble nature of such polymers. The D-galactose distribution in carob galactomannan and in the hot- and cold-water-soluble fractions of carob galactomannan has been shown to be non-regular, with a high proportion of substituted couplets, lesser amounts of triplets, and an absence of blocks of substitution. The probability of sequences in which alternate D-mannosyl residues are substituted is low. The probability distribution of block sizes for unsubstituted D-mannosyl residues indicates that there is a higher proportion of blocks of intermediate size than would be present in a galactomannan with a statistically random D-galactose distribution. Based on the almost identical patterns of amounts of oligosaccharides produced on hydrolysis with β-D-mannanase, it appears that galactomannans from seed of a wide range of carob varities have the same fine-structure. The D-galactose distribution in guar-seed galactomannan also appears to be non-regular, and galactomannans from different guar-seed varieties appear to have the same fine-structure.Hide Abstract
McCleary, B. V. (1983). Carbohydrate Research, 111(2), 297-310.
β-D-Mannosidase (β-D-mannoside mannohydrolase EC 184.108.40.206) was purified 160-fold from crude gut-solution of Helix pomatia by three chromatographic steps and then gave a single protein band (mol. wt. 94,000) on SDS-gel electrophoresis, and three protein bands (of almost identical isoelectric points) on thin-layer iso-electric focusing. Each of these protein bands had enzyme activity. The specific activity of the purified enzyme on p-nitrophenyl β-D-mannopyranoside was 1694 nkat/mg at 40° and it was devoid of α-D-mannosidase, β-D-galactosidase, 2-acet-amido-2-deoxy-D-glucosidase, (1→4)-β-D-mannanase, and (1→4)-β-D-glucanase activities, almost devoid of α-D-galactosidase activity, and contaminated with <0.02% of β-D-glucosidase activity. The purified enzyme had the same Km for borohydride-reduced β-D-manno-oligosaccharides of d.p. 3-5 (12.5mM). The initial rate of hydrolysis of (1→4)-linked β-D-manno-oligosaccharides of d.p. 2-5 and of reduced β-D-manno-oligosaccharides of d.p. 3-5 was the same, and o-nitrophenyl, methylumbelliferyl, and naphthyl β-D-mannopyranosides were readily hydrolysed. β-D-Mannobiose was hydrolysed at a rate ~25 times that of 61-α-D-galactosyl-β-D-mannobiose and 63-α-D-galactosyl-β-D-mannotetraose, and at ~90 times the rate for β-D-mannobi-itol.Hide Abstract
McCleary, B. V. (1983). Phytochemistry, 22(3), 649-658.
Hydrolysis of galactomannan in endosperms of germinating guar is due to the combined action of three enzymes, α-galactosidase, β-mannanase and exo-β-mannanase. α-Galactosidase and exo-β-mannanase activities occur both in endosperm and cotyledon tissue but β-mannanase occurs only in endosperms. On seed germination, β-mannanase and endospermic α-galactosidase are synthesized and activity changes parallel galactomannan degradation. Galactomannan degradation and synthesis of these two enzymes are inhibited by cycloheximide. In contrast, endospermic exo-β-mannanase is not synthesized on seed germination, but rather is already present throughout endosperm tissue. It has no action on native galactomannan. α-Galactosidase, β-mannanase and exo-β-mannanase have been purified to homogeneity and their separate and combined action in the hydrolysis of galactomannan and effect on the rate of uptake of carbohydrate by cotyledons, studied. Results obtained indicated that these three activities are sufficient to account for galactomannan degradation in vivo and, further, that all three are required. Cotyledons contain an active exo-β-mannanase and sugar-uptake experiments have shown that cotyledons can absorb mannobiose intact, indicating that this enzyme is involved in the complete degradation of galactomannan on seed germination.Hide Abstract
McCleary, B. V., Nurthen, E., Taravel, F. R. & Joseleau, J. P. (1983). Carbohydrate Research, 118, 91-109.
Treatment of hot-water-soluble carob galactomannan with β-D-mannanases from A. niger or lucerne seed affords an array of D-galactose-containing β-D-mannosaccharides as well as β-D-manno-biose, -triose, and -tetraose (lucerne-seed enzyme only). The D-galactose-containing β-D-mannosaccharides of d.p. 3–9 produced by A. niger β-D-mannanase have been characterised, using enzymic, n.m.r., and chemical techniques, as 61-α-D-galactosyl-β-D-mannobiose, 61-α-D-galactosyl-β-D-mannotriose, 63,64-di-α-D-galactosyl-β-D-mannopentaose (the only heptasaccharide), and 63,64-di-α-D-galactosyl-β-D-mannohexaose, 64,65-di-α-D-galactosyl-β-D-mannohexaose, and 61, 63,64-tri-α-D-galactosyl-β-D-mannopentaose (the only octasaccharides). Four nonasaccharides have also been characterised. Penta- and hexa-saccharides were absent. Lucerne-seed β-D-mannanase produced the same branched tri-, tetra- and hepta-saccharides, and also penta- and hexa-saccharides that were characterised as 61-α-D-galactosyl-β-D-mannotetraose, 63-α-D-galactosyl-β-D-mannotetraose, 61,63-di-α-D-galactosyl-β-D-mannotetraose, 63-α-D-galactosyl-β-D-mannopentaose, and 64-α-D-galactosyl-β-D-mannopentaose. None of the oligosaccharides contained a D-galactose stub on the terminal D-mannosyl group nor were they substituted on the second D-mannosyl residue from the reducing terminal.Hide Abstract
McCleary, B. V. & Matheson, N. K. (1983). Carbohydrate Research, 119, 191-219.
Purified (1→4)-β-D-mannanase from Aspergillus niger and lucerne seeds has been incubated with mannosaccharides and end-reduced (1→4)-β-D-mannosaccharides and, from the products of hydrolysis, a cyclic reaction-sequence has been proposed. From the heterosaccharides released by hydrolysis of the hot-water-soluble fraction of carob galactomannan by A. niger β-D-mannanase, a pattern of binding between the β-D-mannan chain and the enzyme has been deduced. The products of hydrolysis with the β-D-mannanases from Irpex lacteus, Helix pomatia, Bacillus subtilis, and lucerne and guar seeds have also been determined, and the differences from the action of A. niger β-D-mannanase related to minor differences in substrate binding. The products of hydrolysis of glucomannan are consistent with those expected from the binding pattern proposed from the hydrolysis of galactomannan.Hide Abstract
McCleary, B. V. (1982), Carbohydrate Research, 101(1), 75-92.
A β-D-mannoside mannohydrolase enzyme has been purified to homogeneity from germinated guar-seeds. Difficulties associated with the extraction and purification appeared to be due to an interaction of the enzyme with other protein material. The purified enzyme hydrolysed various natural and synthetic substrates, including β-D-manno-oligosaccharides and reduced β-D-manno-oligosaccharides of degree of polymerisation 2 to 6, as well as p-nitrophenyl, naphthyl, and methylumbelliferyl β-D-mannopyranosides. The preferred, natural substrate was β-D-mannopentaose, which was hydrolysed at twice the rate of β-D-mannotetraose and five times the rate of β-D-mannotriose. This result, together with the observation that α-D-mannose is released on hydrolysis, indicates that the enzyme is an exo-β-D-mannanase.Hide Abstract
McCleary, B. V., Taravel, F. R. & Cheetham, N. W. H. (1982). Carbohydrate Research, 104(2), 285-297.
N.m.r., enzymic, and chemical techniques have been used to characterise the D-galactose-containing tri- and tetra-saccharides produced on hydrolysis of carob and L. leucocephala D-galacto-D-mannans by Driselase β-D-mannanase. These oligosaccharides were shown to be exclusively 61-α-D-galactosyl-β-D-mannobiose and 61-α-D-galactosyl-β-D-mannotriose. Furthermore, these were the only D-galactose-containing tri- and tetra-saccharides produced on hydrolysis of carob D-galacto-D-mannan by β-D-mannanases from other sources, including Bacillus subtilis, Aspergillus niger, Helix pomatia gut solution, and germinated legumes. Acid hydrolysis of lucerne galactomannan yielded 61-α-D-galactosyl-β-D-mannobiose and 62-α-D-galactosyl-β-D-mannobiose.Hide Abstract
An enzymic technique for the quantitation of galactomannan in guar Seeds.
McCleary, B. V. (1981). Lebensmittel-Wissenschaft & Technologie, 14, 56-59.
An enzymic technique has been developed for the rapid and accurate quantitation of the galactomannan content of guar seeds and milling fractions. The technique involves the measurement of the galactose component of galactomannans using galactose dehydrogenase. The galactomannans are converted to galactose and manno-oligosaccharides using partially purified enzymes from a commercial preparation and from germinated guar seeds. Simple procedures have been devised for the preparation of these enzymes. Application of the technique to a number of guar varieties gave values for the galactomannan content ranging from 22.7 to 30.8% of seed weight.Hide Abstract
McCleary, B. V. (1979). Phytochemistry, 18(5), 757-763.
β-Mannanase activities in the commercial enzyme preparations Driselase and Cellulase, in culture solutions of Bacillus subtilis (TX1), in commercial snail gut (Helix pomatia) preparations and in germinated seeds of lucerne, Leucaena leucocephala and honey locust, have been purified by substrate affinity chromatography on glucomannan-AH-Sepharose. On isoelectric focusing, multiple protein bands were found, all of which had β-mannanase activity. Each preparation appeared as a single major band on SDS-polyacrylamide gel electrophoresis. The enzymes varied in their final specific activities, Km values, optimal pH, isoelectric points and pH and temperature stabilities but had similar MWs. The enzymes have different abilities to hydrolyse galactomannans which are highly substituted with galactose. The preparations Driselase and Cellulase contain β-mannanases which can attack highly substituted galactomannans at points of single unsubstituted D-mannosyl residues if the D-galactose residues in the vicinity of the bond to be hydrolysed are all on only one side of the main chain.Hide Abstract
McCleary, B. V., Matheson, N. K. & Small, D. B. (1976). Phytochemistry, 15(7), 1111-1117.
A series of galactomannans with varying degrees of galactose substitution have been extracted from the endosperms of legume seeds with water and alkali and the amount of substitution required for water solubility has been determined. Some were heterogeneous with respect to the degree of galactose substitution. The structural requirements for hydrolysis by plant β-mannanase have been studied using the relative rates and extents of hydrolysis of these galactomannans. A more detailed examination of the products of hydrolysis of carob galactomannan has been made. At least two contiguous anhydromannose units appear to be needed for scission. This is similar to the requirement for hydrolysis by microbial enzymes. Judas tree (Cercis siliquastrum) endosperm contained a polysaccharide with a unique composition for a legume seed reserve. Gel chromatography and electrophoresis on cellulose acetate indicated homogeneity. Hydrolysis with a mixture of β-mannanase and α-galactosidase gave a glucose-mannose disaccharide and acetolysis gave a galactose-mannose. These results, as well as the pattern of hydrolysis by β-mannanase were consistent with a galactoglucomannan structure.Hide Abstract
McCleary, B. V. & Matheson, N. K. (1975). Phytochemistry, 14(5-6), 1187-1194.
Structural changes in galactomannan on germination of lucerne, carob, honey locust, guar and soybean seeds, as measured by viscosity, elution volumes on gel filtration and ultra-centrifugation were slight consistent with a rapid and complete hydrolysis of a molecule once hydrolysis of the mannan chain starts. β-Mannanase activity increased and then decreased, paralleling galactomannan depletion. Multiple forms of β-mannanase were isolated and these were located in the endosperm. β-Mannanase had limited ability to hydrolyse galactomannans with high galactose contents. Seeds containing these galactomannans had very active α-galactosidases. β-Mannosidases were present in both endosperm and cotyledon-embryo and could be separated chromatographically. The level of activity was just sufficient to account for mannose production from manno-oligosaccharides.Hide Abstract
McCleary, B. V. & Matheson, N. K. (1974). Phytochemistry, 13(9), 1747-1757.
Germinating seeds of lucerne, guar, carob and soybean initially depleted raffinose series oligosaccharides and then galactomannan. This depletion was accompanied by a rapid increase and then a decrease in α-galactosidase levels. Lucerne and guar contained two α-galactosidase activities, carob three and soybean four. One of these in each plant, from its location in the endosperm, time of appearance and kinetic behaviour, appeared to be primarily involved in galactomannan hydrolysis. This enzyme in lucerne had MW of 23 000 and could not be separated from β-mannanase by (NH4)2SO4 fractionation, DEAE, CM or SE-cellulose chromatography or gel filtration, but only by polyacrylamide gel electrophoresis. In guar, carob and soybean, it could be separated by ion-exchange chromatography and gel filtration. In lucerne, carob and guar most of the total increase in activity was due to this enzyme. The other α-galactosidases had MWs of about 35 000 and could be separated from β-mannanase by dissection, ion exchange cellulose chromatography and gel filtration. They were located in the cotyledon-embryo and appeared to be primarily involved in galactosylsucrose oligosaccharide hydrolysis.Hide Abstract
Conservation of endo-glucanase 16 (EG16) activity across highly divergent plant lineages.
Behar, H., Tamura, K., Wagner, E. R., Cosgrove, D. J., & Brumer, H. (2021). Biochemical Journal, 478(16), 3063-3078.
Plant cell walls are highly dynamic structures that are composed predominately of polysaccharides. As such, endogenous carbohydrate active enzymes (CAZymes) are central to the synthesis and subsequent modification of plant cells during morphogenesis. The endo-glucanase 16 (EG16) members constitute a distinct group of plant CAZymes, angiosperm orthologs of which were recently shown to have dual β-glucan/xyloglucan hydrolase activity. Molecular phylogeny indicates that EG16 members comprise a sister clade with a deep evolutionary relationship to the widely studied apoplastic xyloglucan endo-transglycosylases/hydrolases (XTH). A cross-genome survey indicated that EG16 members occur as a single ortholog across species and are widespread in early diverging plants, including the non-vascular bryophytes, for which functional data were previously lacking. Remarkably, enzymological characterization of an EG16 ortholog from the model moss Physcomitrella patens (PpEG16) revealed that EG16 activity and sequence/structure are highly conserved across 500 million years of plant evolution, vis-à-vis orthologs from grapevine and poplar. Ex vivo biomechanical assays demonstrated that the application of EG16 gene products caused abrupt breakage of etiolated hypocotyls rather than slow extension, thereby indicating a mode-of-action distinct from endogenous expansins and microbial endo-glucanases. The biochemical data presented here will inform future genomic, genetic, and physiological studies of EG16 enzymes.Hide Abstract
Role of carbohydrate binding module (CBM3c) of GH9 β-1, 4 endoglucanase (Cel9W) from Hungateiclostridium thermocellum ATCC 27405 in catalysis.
Kumar, K., Singal, S. & Goyal, A. (2019). Carbohydrate research, 484, 107782.
The function of CBM3c in the enzymatic catalysis varies among the members of family 9 Glycoside Hydrolases (GH). A new member of family 9 GH (Cel9W) from thermophilic anaerobic bacterium, Hungateiclostridium thermocellum was explored for elucidation of the role of CBM3c in catalysis by GH9. Cel9W is a multimodular theme B1, cellulase enzyme comprising a catalytic module of family 9 glycoside hydrolase (HtGH9t) at N-terminal, a family 3c carbohydrate binding module (HtCBM3c) and a dockerin domain at the C-terminal. The ORF of Cel9W encoding full length β-1,4-glucanase, HtGH9 (containing both GH9 and CBM3c modules), the truncated GH9 catalytic module (HtGH9t) and module CBM3c (HtCBM3c) were cloned and over-expressed using E. coli BL21 cells. HtGH9 showed maximum activity at pH 6.5 and 90°C. It displayed highest activity of 64 U/mg against lichenan followed by 44.6 U/mg (β-glucan) and 22.3 U/mg (Carboxymethyl cellulose). HtGH9 showed stability in the pH ranging from 5.0 to 9.0 and thermal stability up to 70°C for 1.0 h. The presence of EDTA and EGTA decreased the activity of HtGH9 and also shifted the melting curve peak from 93°C to 88°C indicating that the enzyme inherently possesses metal ions, which play role in catalysis and structural stability. The TLC analysis of HtGH9 hydrolysed Avicel showed the presence cellotetraose indicating the processive endoglucanase activity in HtGH9. The module, HtGH9t alone exhibited very low level of activity (1.22 U/mg) against lichenan. It partially recovered (51%) the enzyme activity in presence of equimolar concentration of HtCBM3c. Non-denaturing gel electrophoresis revealed a non-covalent binding interaction between the catalytic HtGH9t module with HtCBM3c module and their physical association showed the partial recovery of its endoglucanase activity. This study confirmed that the physical association of the catalytic module HtGH9t with HtCBM3c is necessary for HtGH9 to efficiently hydrolyze the cellulosic substrates.Hide Abstract
A novel fungal GH30 xylanase with xylobiohydrolase auxiliary activity.
Katsimpouras, C., Dedes, G., Thomaidis, N. S. & Topakas, E. (2019). Biotechnology for Biofuels, 12(1), 120.
Background: The main representatives of hemicellulose are xylans, usually decorated β-1,4-linked D-xylose polymers, which are hydrolyzed by xylanases. The efficient utilization and complete hydrolysis of xylans necessitate the understanding of the mode of action of xylan degrading enzymes. The glycoside hydrolase family 30 (GH30) xylanases comprise a less studied group of such enzymes, and differences regarding the substrate recognition have been reported between fungal and bacterial GH30 xylanases. Besides their role in the utilization of lignocellulosic biomass for bioenergy, such enzymes could be used for the tailored production of prebiotic xylooligosaccharides (XOS) due to their substrate specificity. Results: The expression of a putative GH30_7 xylanase from the fungus Thermothelomyces thermophila (synonyms Myceliophthora thermophila, Sporotrichum thermophile) in Pichia pastoris resulted in the production and isolation of a novel xylanase with unique catalytic properties. The novel enzyme designated TtXyn30A, exhibited an endo- mode of action similar to that of bacterial GH30 xylanases that require 4-O-methyl-D-glucuronic acid (MeGlcA) decorations, in contrast to most characterized fungal ones. However, TtXyn30A also exhibited an exo-acting catalytic behavior by releasing the disaccharide xylobiose from the non-reducing end of XOS. The hydrolysis products from beechwood glucuronoxylan were MeGlcA substituted XOS, and xylobiose. The major uronic XOS (UXOS) were the aldotriuronic and aldotetrauronic acid after longer incubation indicating the ability of TtXyn30A to cleave linear parts of xylan and UXOS as well. Conclusions: Hereby, we reported the heterologous production and biochemical characterization of a novel fungal GH30 xylanase exhibiting endo- and exo-xylanase activity. To date, considering its novel catalytic properties, TtXyn30A shows differences with most characterized fungal and bacterial GH30 xylanases. The discovered xylobiohydrolase mode of action offers new insights into fungal enzymatic systems that are employed for the utilization of lignocellulosic biomass. The recombinant xylanase could be used for the production of X2 and UXOS from glucuronoxylan, which in turn would be utilized as prebiotics carrying manifold health benefits.Hide Abstract
A novel thermostable GH10 xylanase with activities on a wide variety of cellulosic substrates from a xylanolytic Bacillus strain exhibiting significant synergy with commercial Celluclast 1.5 L in pretreated corn stover hydrolysis.
Wang, K., Cao, R., Wang, M., Lin, Q., Zhan, R., Xu, H. & Wang, S. (2019). Biotechnology for Biofuels, 12(1), 48.
Background: Cellulose and hemicellulose are the two largest components in lignocellulosic biomass. Enzymes with activities towards cellulose and xylan have attracted great interest in the bioconversion of lignocellulosic biomass, since they have potential in improving the hydrolytic performance and reducing the enzyme costs. Exploring glycoside hydrolases (GHs) with good thermostability and activities on xylan and cellulose would be beneficial to the industrial production of biofuels and bio-based chemicals. Results: A novel GH10 enzyme (XynA) identified from a xylanolytic strain Bacillus sp. KW1 was cloned and expressed. Its optimal pH and temperature were determined to be pH 6.0 and 65°C. Stability analyses revealed that XynA was stable over a broad pH range (pH 6.0-11.0) after being incubated at 25°C for 24 h. Moreover, XynA retained over 95% activity after heat treatment at 60°C for 60 h, and its half-lives at 65°C and 70°C were about 12 h and 1.5 h, respectively. More importantly, in terms of substrate specificity, XynA exhibits hydrolytic activities towards xylans, microcrystalline cellulose (filter paper and Avicel), carboxymethyl cellulose (CMC), cellobiose, p-nitrophenyl-β-D-cellobioside (pNPC), and p-nitrophenyl-β-D-glucopyranoside (pNPG). Furthermore, the addition of XynA into commercial cellulase in the hydrolysis of pretreated corn stover resulted in remarkable increases (the relative increases may up to 90%) in the release of reducing sugars. Finally, it is worth mentioning that XynA only shows high amino acid sequence identity (88%) with rXynAHJ14, a GH10 xylanase with no activity on CMC. The similarities with other characterized GH10 enzymes, including xylanases and bifunctional xylanase/cellulase enzymes, are no more than 30%. Conclusions: XynA is a novel thermostable GH10 xylanase with a wide substrate spectrum. It displays good stability in a broad range of pH and high temperatures, and exhibits activities towards xylans and a wide variety of cellulosic substrates, which are not found in other GH10 enzymes. The enzyme also has high capacity in saccharification of pretreated corn stover. These characteristics make XynA a good candidate not only for assisting cellulase in lignocellulosic biomass hydrolysis, but also for the research on structure-function relationship of bifunctional xylanase/cellulase.Hide Abstract
Wood-Derived Dietary Fibers Promote Beneficial Human Gut Microbiota.
Rosa, S. L. L., Vasiliki, K., Fanny, B., Pope, P. B., Pudlo, N. A., Martens, E. C., Rastall, R. A., et al. (2019). mSphere, 4(1), 1-16.
Woody biomass is a sustainable and virtually unlimited source of hemicellulosic polysaccharides. The predominant hemicelluloses in softwood and hardwood are galactoglucomannan (GGM) and arabinoglucuronoxylan (AGX), respectively. Based on the structure similarity with common dietary fibers, GGM and AGX may be postulated to have prebiotic properties, conferring a health benefit on the host through specific modulation of the gut microbiota. In this study, we evaluated the prebiotic potential of acetylated GGM (AcGGM) and highly acetylated AGX (AcAGX) obtained from Norwegian lignocellulosic feedstocks in vitro. In pure culture, both substrates selectively promoted the growth of Bifidobacterium, Lactobacillus, and Bacteroides species in a manner consistent with the presence of genetic loci for the utilization of -manno-oligosaccharides/-mannans and xylo-oligosaccharides/ xylans. The prebiotic potential of AcGGM and AcAGX was further assessed in a pH controlled batch culture fermentation system inoculated with healthy adult human feces. Results were compared with those obtained with a commercial fructooligosaccharide (FOS) mixture. Similarly to FOS, both substrates significantly increased (P < 0.05) the Bifidobacterium population. Other bacterial groups enumerated were unaffected with the exception of an increase in the growth of members of the Bacteroides-Prevotella group, Faecalibacterium prausnitzii, and clostridial cluster IX (P < 0.05). Compared to the other substrates, AcGGM promoted butyrogenic fermentation whereas AcAGX was more propiogenic. Although further in vivo confirmation is necessary, these results demonstrate that both AcGGM and AcAGX from lignocellulosic feedstocks can be used to direct the promotion of beneficial bacteria, thus exhibiting a promising prebiotic ability to improve or restore gut health.Hide Abstract