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D-Glucuronic/D-Galacturonic Acid Assay Kit

Product code: K-URONIC

100 assays (manual) / 1000 assays (microplate) / 1000 assays (auto-analyser)

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Content: 100 assays (manual) / 1000 assays (microplate) / 1000 assays (auto-analyser)
Shipping Temperature: Ambient
Storage Temperature: Short term stability: 2-8oC,
Long term stability: See individual component labels
Stability: > 2 years under recommended storage conditions
Analyte: D-Galacturonic Acid, D-Glucuronic Acid
Assay Format: Spectrophotometer, Microplate, Auto-analyser
Detection Method: Absorbance
Wavelength (nm): 340
Signal Response: Increase
Linear Range: 5 to 150 µg of D-glucuronic acid or D-galacturonic acid per assay
Limit of Detection: ~ 15.5 mg/L
Reaction Time (min): ~ 10 min at 25oC or ~ 5 min at 37oC
Application examples: Hydrolysates of plant material and polysaccharides and other materials.
Method recognition: Novel method

The D-Glucuronic/D-Galacturonic test kit is a simple, reliable and accurate method for the measurement and analysis of D-hexuronic acids (specifically D-glucuronic acid and D-galacturonic acid) in plant extracts, culture media/supernatants and other materials.

Note for Content: The number of manual tests per kit can be doubled if all volumes are halved.  This can be readily accommodated using the MegaQuantTM  Wave Spectrophotometer (D-MQWAVE).

See our complete range of mono/disaccharide test kits.

Scheme-K-URONIC URONIC Megazyme

  • Very cost effective 
  • All reagents stable for > 2 years during use 
  • Only test kit available 
  • Simple format 
  • Mega-Calc™ software tool is available from our website for hassle-free raw data processing 
  • Standard included 
  • Suitable for manual, microplate and auto-analyser formats
Certificate of Analysis
Safety Data Sheet
FAQs Assay Protocol Data Calculator Validation Report
Megazyme publication

Measurement of available carbohydrates in cereal and cereal products, dairy products, vegetables, fruit and related food products and animal feeds: First Action 2020.07.

McCleary, B. V. & McLoughlin, C. (2021). Journal of AOAC International, qsab019.

Background: The level of available carbohydrates in our diet is directly linked to two major diseases; obesity and Type II diabetes. Despite this, to date there is no method available to allow direct and accurate measurement of available carbohydrates in human and animal foods. Objective: The aim of this research was to develop a method that would allow simple and accurate measurement of available carbohydrates, defined as non-resistant starch, maltodextrins, maltose, isomaltose, sucrose, lactose, glucose, fructose and galactose. Method: Non-resistant (digestible) starch is hydrolysed to glucose and maltose by pancreatic α-amylase and amyloglucosidase at pH 6.0 with shaking or stirring at 37°C for 4 h. Sucrose, lactose, maltose and isomaltose are completely hydrolyzed by specific enzymes to their constituent monosaccharides, which are then measured using pure enzymes in a single reaction cuvette. Results: A method has been developed that allows the accurate measurement of available carbohydrates in all cereal, vegetable, fruit, food, and feed products, including dairy products. Conclusions: A single-laboratory validation was performed on a wide range of food and feed products. The inter-day repeatability (%RSDr) was <3.58% (w/w) across a range of samples containing 44.1 to 88.9% available carbohydrates. The LOD and LOQ obtained were 0.054% (w/w) and 0.179% (w/w), respectively. The method is all inclusive, specific, robust and simple to use. Highlights: A unique method has been developed for the direct measurement of available carbohydrates, entailing separate measurement of glucose, fructose and galactose; information of value in determining the glycemic index of foods.

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A Combination approach in inhibiting Type 2 diabetes-related enzymes using Ecklonia radiata fucoidan and acarbose.

Mabate, B., Daub, C. D., Malgas, S., Edkins, A. L. & Pletschke, B. I. (2021). Pharmaceutics, 13(11), 1979.

Although there are chemotherapeutic efforts in place for Type 2 diabetes mellitus (T2DM), there is a need for novel strategies (including natural products) to manage T2DM. Fucoidan, a sulphated polysaccharide was extracted from Ecklonia radiata. The integrity of the fucoidan was confirmed by structural analysis techniques such as FT-IR, NMR and TGA. In addition, the fucoidan was chemically characterised and tested for cell toxicity. The fucoidan was investigated with regards to its potential to inhibit α-amylase and α-glucosidase. The fucoidan was not cytotoxic and inhibited α-glucosidase (IC50 19 µg/mL) more strongly than the standard commercial drug acarbose (IC50 332 µg/mL). However, the fucoidan lacked potency against α-amylase. On the other hand, acarbose was a more potent inhibitor of α-amylase (IC50 of 109 µg/mL) than α-glucosidase. Due to side effects associated with the use of acarbose, a combination approach using acarbose and fucoidan was investigated. The combination showed synergistic inhibition (>70%) of α-glucosidase compared to when the drugs were used alone. The medicinal implication of this synergism is that a regimen with a reduced acarbose dose may be used, thus minimising side effects to the patient, while achieving the desired therapeutic effect for managing T2DM.

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Inositol metabolism regulates capsule structure and virulence in the human pathogen Cryptococcus neoformans.

Wang, Y., Wear, M., Kohli, G., Vij, R., Giamberardino, C., Shah, A., Toffaletti, D. L., Yu, C. A., Perfect, J. R., Casadevall, A. & Xue, C. (2021). Mbio, 12(6), e02790-21.

The environmental yeast Cryptococcus neoformans is the most common cause of deadly fungal meningitis in primarily immunocompromised populations. A number of factors contribute to cryptococcal pathogenesis. Among them, inositol utilization has been shown to promote C. neoformans development in nature and invasion of central nervous system during dissemination. The mechanisms of the inositol regulation of fungal virulence remain incompletely understood. In this study, we analyzed inositol-induced capsule growth and the contribution of a unique inositol catabolic pathway in fungal development and virulence. We found that genes involved in the inositol catabolic pathway are highly induced by inositol, and they are also highly expressed in the cerebrospinal fluid of patients with meningoencephalitis. This pathway in C. neoformans contains three genes encoding myo-inositol oxygenases that convert myo-inositol into d-glucuronic acid, a substrate of the pentose phosphate cycle and a component of the polysaccharide capsule. Our mutagenesis analysis demonstrates that inositol catabolism is required for C. neoformans virulence and deletion mutants of myo-inositol oxygenases result in altered capsule growth as well as the polysaccharide structure, including O-acetylation. Our study indicates that the ability to utilize the abundant inositol in the brain may contribute to fungal pathogenesis in this neurotropic fungal pathogen.

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Efficient production of nutraceuticals and lactic acid from lignocellulosic biomass by combining organosolv fractionation with enzymatic/fermentative routes.

Karnaouri, A., Asimakopoulou, G., Kalogiannis, K. G., Lappas, A. A. & Topakas, E. (2021). Bioresource Technology, 341, 125846.

The aim of this work was to investigate the use of isobutanol as organic solvent for the efficient delignification and fractionation of beechwood through the OxiOrganosolv process in the absence of any catalyst. The results demonstrate that cellulose-rich solid pulp produced after pretreatment is a source of fermentable sugars that can be easily hydrolyzed and serve as a carbon source in microbial fermentations for the production of omega-3 fatty acids and D-lactic acid. The C5 sugars are recovered in the aqueous liquid fractions and comprise a fraction rich in xylo-oligosaccharides with prebiotic potential. The maximum production of optically pure D-lactic from Lactobacillus delbrueckii sp. bulgaricus reached 51.6 g/L (0.57 g/gbiomass), following a simultaneous saccharification and fermentation strategy. Crypthecodenium cohnii accumulated up to 52.1 wt% lipids with a DHA content of 54.1 %, while up to 43.3 % hemicellulose recovery in form of oligosaccharides was achieved in the liquid fraction.

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Characterization of a novel multidomain CE15-GH8 enzyme encoded by a polysaccharide utilization locus in the human gut bacterium Bacteroides eggerthii.

Kmezik, C., Krska, D., Mazurkewich, S. & Larsbrink, J. (2021). Scientific Reports, 11(1), 1-13.

Bacteroidetes are efficient degraders of complex carbohydrates, much thanks to their use of polysaccharide utilization loci (PULs). An integral part of PULs are highly specialized carbohydrate-active enzymes, sometimes composed of multiple linked domains with discrete functions-multicatalytic enzymes. We present the biochemical characterization of a multicatalytic enzyme from a large PUL encoded by the gut bacterium Bacteroides eggerthii. The enzyme, BeCE15A-Rex8A, has a rare and novel architecture, with an N-terminal carbohydrate esterase family 15 (CE15) domain and a C-terminal glycoside hydrolase family 8 (GH8) domain. The CE15 domain was identified as a glucuronoyl esterase (GE), though with relatively poor activity on GE model substrates, attributed to key amino acid substitutions in the active site compared to previously studied GEs. The GH8 domain was shown to be a reducing-end xylose-releasing exo-oligoxylanase (Rex), based on having activity on xylooligosaccharides but not on longer xylan chains. The full-length BeCE15A-Rex8A enzyme and the Rex domain were capable of boosting the activity of a commercially available GH11 xylanase on corn cob biomass. Our research adds to the understanding of multicatalytic enzyme architectures and showcases the potential of discovering novel and atypical carbohydrate-active enzymes from mining PULs.

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The protective effect of Scenedesmus dimorphus polysaccharide as an antioxidant and antiaging agent on aging rat model induced by D-galactose.

Armaini, A. & Imelda, I. (2021). Journal of Applied Pharmaceutical Science, 11(05), 054-063.

Premature skin aging occurs due to the increased formation of reactive oxygen species (ROS), which causes oxidative stress, DNA damage, and collagen degradation. This study investigates the protective effect of Scenedesmus dimorphus polysaccharides (SDP) as an antioxidant and anti-aging agent on an aging rat model induced by D-galactose (D-gal). This study used 48 male Wistar rats divided into six groups: (1) normal control, (2) polysaccharide control, (3) aging control induced by D-gal 0.25 mg/g bw/days, (4) drug control (vitamin E) treated twice with SDP in an aging rat model, (5) D-gal + SDP (0.2 mg/g bw), and (6) D-gal + SDP (0.8 mg/g bw) treated with oral treatment and observed for periods of 2, 4, and 8 weeks. Giving SDP at a dose of 0.8 mg/g bw can increase superoxide dismutases and catalase activity and reduce malondialdehyde after 8 weeks of observation, which is better than giving vitamin E. The treatment of SDP can stimulate collagen synthesis and reduce advanced glycation end products. Histopathology shows an increase in the area of fibrocollagen proportions and deposition from the matrix on giving SDP, which is better than vitamin E, since SDP can repair skin tissue. Thus, SDP can be useful as an antioxidant and anti-aging agent in an aging Wistar rats model.

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A new, quick, and simple protocol to evaluate microalgae polysaccharide composition.

Decamp, A., Michelo, O., Rabbat, C., Laroche, C., Grizeau, D., Pruvost, J. & Gonçalves, O. (2021). Marine Drugs, 19(2), 101.

In this work, a new methodological approach, relying on the high specificity of enzymes in a complex mixture, was developed to estimate the composition of bioactive polysaccharides produced by microalgae, directly in algal cultures. The objective was to set up a protocol to target oligomers commonly known to be associated with exopolysaccharides’ (EPS) nutraceutical and pharmaceutical activities (i.e., rhamnose, fucose, acidic sugars, etc.) without the constraints classically associated with chromatographic methods, while maintaining a resolution sufficiently high to enable their monitoring in the culture system. Determination of the monosaccharide content required the application of acid hydrolysis (2 M trifluoroacetic acid) followed by NaOH (2 M) neutralization. Quantification was then carried out directly on the fresh hydrolysate using enzyme kits corresponding to the main monosaccharides in a pre-determined composition of the polysaccharides under analysis. Initial results showed that the enzymes were not sensitive to the presence of TFA and NaOH, so the methodology could be carried out on fresh hydrolysate. The limits of quantification of the method were estimated as being in the order of the log of nanograms of monosaccharides per well, thus positioning it among the chromatographic methods in terms of analytical performance. A comparative analysis of the results obtained by the enzymatic method with a reference method (high-performance anion-exchange chromatography) confirmed good recovery rates, thus validating the closeness of the protocol. Finally, analyses of raw culture media were carried out and compared to the results obtained in miliQ water; no differences were observed. The new approach is a quick, functional analysis method allowing routine monitoring of the quality of bioactive polysaccharides in algal cultures grown in photobioreactors.

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Investigation of a thermostable multi-domain xylanase-glucuronoyl esterase enzyme from Caldicellulosiruptor kristjanssonii incorporating multiple carbohydrate-binding modules.

Krska, D. & Larsbrink, J. (2020). Biotechnology for Biofuels, 13, 1-13.

Background: Efficient degradation of lignocellulosic biomass has become a major bottleneck in industrial processes which attempt to use biomass as a carbon source for the production of biofuels and materials. To make the most effective use of the source material, both the hemicellulosic as well as cellulosic parts of the biomass should be targeted, and as such both hemicellulases and cellulases are important enzymes in biorefinery processes. Using thermostable versions of these enzymes can also prove beneficial in biomass degradation, as they can be expected to act faster than mesophilic enzymes and the process can also be improved by lower viscosities at higher temperatures, as well as prevent the introduction of microbial contamination. Results: This study presents the investigation of the thermostable, dual-function xylanase-glucuronoyl esterase enzyme CkXyn10C-GE15A from the hyperthermophilic bacterium Caldicellulosiruptor kristjanssonii. Biochemical characterization of the enzyme was performed, including assays for establishing the melting points for the different protein domains, activity assays for the two catalytic domains, as well as binding assays for the multiple carbohydrate-binding domains present in CkXyn10C-GE15A. Although the enzyme domains are naturally linked together, when added separately to biomass, the expected boosting of the xylanase action was not seen. This lack of intramolecular synergy might suggest, together with previous data, that increased xylose release is not the main beneficial trait given by glucuronoyl esterases. Conclusions: Due to its thermostability, CkXyn10C-GE15A is a promising candidate for industrial processes, with both catalytic domains exhibiting melting temperatures over 70°C. Of particular interest is the glucuronoyl esterase domain, as it represents the first studied thermostable enzyme displaying this activity.

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Tailored and synergistic enzyme-assisted extraction of carotenoid-containing chromoplasts from tomatoes.

Lombardelli, C., Liburdi, K., Benucci, I. & Esti, M. (2020). Food and Bioproducts Processing, 121, 43-53.

Despite significant efforts recently made to improve the recovery yield of food pigments from natural sources, the development of green and sustainable biotechnological approaches is currently under investigation. Within the context of circular economy, food wastes represent a cheap source for the recovery of valuable compounds including food ingredients. In this study, a conservative approach consisting in a tailored enzyme-assisted extraction protocol for the recovery of carotenoid-containing chromoplasts from unsold tomatoes in which lycopene is stable and protected against oxidation, has now been developed. A tailored enzymatic mix based on polygalacturonase, pectin lyase, cellulase and xylanase, has been designed taking into account the polysaccharide composition of the tomato cell wall. The optimal process conditions for enhancing the recovery of carotenoids from tomatoes i.e.; temperature, pH, enzymatic mix of total dosage and processing time, have been investigated. The suitable temperature and pH identified by the RSM analysis, were found to be: 45-55°C at pH 5-5.5. The treatment carried out using the total dosage of 25 U/g for 180 min was the most convenient for maximizing the recovery yield [about 4.30 ± 0.08 (mgLyc/Kgtomato)/U as carotenoid-containing chromoplasts and about 5.43 ± 0.04 (mgLyc/Kgtomato)/U as total carotenoids].

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Vegetable wastes derived polysaccharides as natural eco-friendly plasticizers of sodium alginate.

Di Donato, P., Taurisano, V., Poli, A., d’Ayala, G. G., Nicolaus, B., Malinconinco, M. & Santagata, G. (2020). Carbohydrate polymers, 229, 115427.

In this paper, lemon and fennel wastes were recovered and used as secondary-raw polysaccharide sources. These polysaccharides were exploited as natural plasticizers of sodium alginate (A) based films, in order to improve sodium alginate performances, limited by its fragility, extending its potential application in a cost effective and eco-friendly way. Different green processes, such as maceration (MAC), ultrasound assisted extraction (UAE) and microwave assisted extraction (MAE), were carried out for obtaining high yield of lemon and fennel polysaccharides (LP and FP). Actually, HPAE-PAD and TLC analyses evidenced the presence of xyslose, galactose, glucose and rhamnose monomers and galacturonic acid, typical of polysaccharides like pectin and xyloglucan chains. These findings were confirmed by NMR and FTIR spectroscopic analyses. Moreovers, gel filtration chromatography assessed the high molecular weight of recovered polysaccharides, particularly of FP waste fraction. The extracted polysaccharides were used as eco-friendly and cost-effective plasticizers of sodium alginate films (AFP and ALP). DSC analysis evidenced a significant decreasing of glass transition temperature of the polymer, tensile tests showed an enlightened rising of elongation at break and TGA analysis showed a faster degradation kinetics of AFP and ALP films, as expected in a plasticized system.

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Interactions of anthocyanins with pectin and pectin fragments in model solutions.

Larsen, L. R., Buerschaper, J., Schieber, A. & Weber, F. (2019). Journal of Agricultural and Food Chemistry, 67(33), 9344-9353.

Anthocyanins determine the color and potential health-promoting properties of red fruit juices, but the juices contain remarkably less anthocyanins than the fruits, which is partly caused by the interactions of anthocyanins with the residues of cell wall polysaccharides like pectin. In this study, pectin was modified by ultrasound and enzyme treatments to residues of polysaccharides and oligosaccharides widely differing in their molecular weight. Modifications decreased viscosity and degrees of acetylation and methylation and released smooth and hairy region fragments. Native and modified pectin induced different effects on the concentrations of individual anthocyanins after short-term and long-term incubation caused by both hydrophobic and hydrophilic interactions. Results indicate that both pectin and anthocyanin structure influence these interactions. Linear polymers generated by ultrasound formed insoluble anthocyanin complexes, whereas oligosaccharides produced by enzymes formed soluble complexes with protective properties. The structure of the anthocyanin aglycone apparently influenced interactions more than the sugar moiety.

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Structure-function analyses reveal that a glucuronoyl esterase from Teredinibacter turnerae interacts with carbohydrates and aromatic compounds.

Bååth, J. A., Mazurkewich, S., Poulsen, J. C. N., Olsson, L., Leggio, L. L. & Larsbrink, J. (2019). Journal of Biological Chemistry, 294(16), 6635-6644.

Glucuronoyl esterases (GEs) catalyze the cleavage of ester linkages found between lignin and glucuronic acid moieties on glucuronoxylan in plant biomass. As such, GEs represent promising biochemical tools in industrial processing of these recalcitrant resources. However, details on how GEs interact with their natural substrates are sparse, calling for thorough structure-function studies. Presented here is the structure and biochemical characterization of a GE, TtCE15A, from the bacterium Teredinibacter turnerae, a symbiont of wood-boring shipworms. To gain deeper insight into enzyme-substrate interactions, inhibition studies were performed with both the WT TtCE15A and variants in which we, by using site-directed mutagenesis, substituted residues suggested to have key roles in binding to or interacting with the aromatic and carbohydrate structures of its uronic acid ester substrates. Our results support the hypothesis that two aromatic residues (Phe-174 and Trp-376), conserved in bacterial GEs, interact with aromatic and carbohydrate structures of these substrates in the enzyme active site, respectively. The solved crystal structure of TtCE15A revealed features previously not observed in either fungal or bacterial GEs, with a large inserted N-terminal region neighboring the active site and a differently positioned residue of the catalytic triad. The findings highlight key interactions between GEs and complex lignin-carbohydrate ester substrates and advance our understanding of the substrate specificities of these enzymes in biomass conversion.

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Rheological and structural characterisation of whey protein acid gels co-structured with chia (Salvia hispanica L.) or flax seed (Linum usitatissimum L.) mucilage.

Soukoulis, C., Cambier, S., Serchi, T., Tsevdou, M., Gaiani, C., Ferrer, P., Taoulis, P. S. & Hoffmann, L. (2019). Food Hydrocolloids, 89, 542-553.

The effects of different plant seed mucilage (PSM) extracts, namely chia seed (CSM) and flaxseed (FSM), on the kinetics of δ-glucono-lactone induced acidification and gelation phenomena of whey proteins (5% w/w WPI) were investigated. The rheological and microstructural properties of mixed whey protein-PSM (0.05-0.75% w/w) cold-set gels produced at 30 or 37°C were studied by means of oscillatory rheology and confocal microscopy. On exceeding 0.125% of PSM, a significant reduction of the gelation time due to the formation of loosely entangled whey protein soluble aggregates was observed. The impact of PSM on the gelation rates was closely related to the PSM type and concentration. CSM addition induced a gradual reduction of maximal gelation rate over the entire concentration range tested. On the other hand, FSM conferred a steep impedance of the gelation when exceeded 0.375%, which was associated with the occurrence of segregative phase separation. Fitting the elastic modulus - gelation time data to a model adapted to the Flory-Stockmayer theory, it was demonstrated that the presence of PSM inhibits the whey protein crosslinking capacity under both tested acidification regimes, leading to the formation of shorter protein crosslinks and therefore, to lower gel stiffness. However, the formation rate of elastically active chain networks was found to be increasing for CSM and FSM contents up to 0.5 and 0.25% respectively, suggesting a synergistic acid gel structuring effect of PSM under these conditions.

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Characterisation of three fungal glucuronoyl esterases on glucuronic acid ester model compounds.

Hüttner, S., Klaubauf, S., de Vries, R. P. & Olsson, L. (2017). Applied Microbiology and Biotechnology, 1-11.

The glucuronoyl esterases (GEs) that have been identified so far belong to family 15 of the carbohydrate esterases in the CAZy classification system and are presumed to target ester bonds between lignin alcohols and (4-O-methyl-)D-glucuronic acid residues of xylan. Few GEs have been cloned, expressed and characterised to date. Characterisation has been done on a variety of synthetic substrates; however, the number of commercially available substrates is very limited. We identified novel putative GEs from a wide taxonomic range of fungi and expressed the enzymes originating from Acremonium alcalophilum and Wolfiporia cocos as well as the previously described PcGE1 from Phanerochaete chrysosporium. All three fungal GEs were active on the commercially available compounds benzyl glucuronic acid (BnGlcA), allyl glucuronic acid (allylGlcA) and to a lower degree on methyl glucuronic acid (MeGlcA). The enzymes showed pH stability over a wide pH range and tolerated 6-h incubations of up to 50°C. Kinetic parameters were determined for BnGlcA. This study shows the suitability of the commercially available model compounds BnGlcA, MeGlcA and allylGlcA in GE activity screening and characterisation experiments. We enriched the spectrum of characterised GEs with two new members of a relatively young enzyme family. Due to its biotechnological significance, this family deserves to be more extensively studied. The presented enzymes are promising candidates as auxiliary enzymes to improve saccharification of plant biomass.

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Action of a GH115 α-glucuronidase from Amphibacillus xylanus at alkaline condition promotes release of 4-O -methylglucopyranosyluronic acid from glucuronoxylan and arabinoglucuronoxylan.

Yan, R., Vuong, T. V., Wang, W. & Master, E. R. (2017). Enzyme and Microbial Technology, 104, 22-28.

Glucuronic acid and/or 4-O-methyl-glucuronic acid (GlcA/MeGlcA) are substituents of the main xylans present in hardwoods, conifers, and many cereal grains. α-Glucuronidases from glycoside hydrolase family GH115 can target GlcA/MeGlcA from both internally and terminally substituted regions of xylans. The current study describes the first GH115 α-glucuronidase, AxyAgu115A, from the alkaliphilic organism Amphilbacillus xylanus. AxyAgu115A was active in a wide pH range, and demonstrated better performance in alkaline condition compared to other characterized GH115 α-glucuronidases, which generally show optimal activity in acidic conditions. Specifically, its relative activity between pH 5.0 and pH 8.5 was above 80%, and was 35% of maximum at pH 10.5; although the enzyme lost 30% and 80% relative residual activity after 24-h pre-incubation at pH 9 and pH 10, respectively. AxyAgu115A was also similarly active towards glucuronoxylan as well as comparatively complex xylans such as spruce arabinoglucurunoxylan. Accommodation of complex xylans was supported by docking analyses that predicted accessibility of AxyAgu115A to branched xylo-oligosaccharides. MeGlcA release by AxyAgu115A from each xylan sample was increased by up to 30% by performing the reaction at pH 11.0 rather than pH 4.0, revealing applied benefits of AxyAgu115A for xylan recovery and processing.

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Fungal glucuronoyl esterases: genome mining based enzyme discovery and biochemical characterization.

Dilokpimol, A., Mäkelä, M. R., Cerullo, G., Zhou, M., Varriale, S., Gidijala, L., Brás, J. L. A.,Jütten, P., Piechot, A., Verhaert, R., Faraco, V., Hilden, K. S. & de Vries, R. P. (2017). New Biotechnology, 40, 282-287.

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 (, 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.

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Kinetic properties of Rhizopus oryzae RPG1 endo-polygalacturonase hydrolyzing galacturonic acid oligomers.

Mertens, J. A. & Bowman, M. J. (2016). Biocatalysis and Agricultural Biotechnology, 5, 11-16.

The kinetic characteristics of Rhizopus oryzae endo-polygalacturonase, RPG1, hydrolyzing galacturonic acid oligomers (GalpA)n were determined. RPG1 generates (GalpA)3 as a dominant product of polygalacturonic acid and (GalpA)4-6 hydrolysis. The enzyme can hydrolyze (GalpA)3, but hydrolysis occurs at a significantly lower rate relative to oligomers with a higher degree of polymerization. Hydrolysis of the α-1,4 glycosidic bond by RPG1 is an endothermic process with a δHapp, of 1.03±0.04 kcal/mol. Determination of kinetic constants by isothermal titration calorimetry showed that for oligomers (GalpA)3-6, the Km decreased and the Kcat increased as the length of the (GalpA) oligomer increased. Fixed time point assays followed by chromatographic analysis provided apparent Kcat values similar to those found using isothermal titration calorimetry. Assays to determine to what extent the enzyme is subject to product inhibition demonstrated that the enzyme is competitively inhibited by (GalpA)2 when using (GalpA)4 as substrate. The apparent Ki of 767 µM is significantly higher than the Km values obtained for the series of galacturonic acid oligomers.

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Fractionation and improved enzymatic deconstruction of hardwoods with alkaline delignification.

Stoklosa, R. J. & Hodge, D. B. (2015). BioEnergy Research, 8(3), 1224-1234.

In this work, an alkaline delignification was investigated for several industrially relevant hardwoods to understand the kinetics of xylan solubilization and degradation and the role of residual lignin content in setting cell wall recalcitrance to enzymatic hydrolysis. Between 34 and 50 % of the xylan was solubilized during the heat-up stage of the pretreatment and undergoes degradation, depolymerization, as well as substantial disappearance of the glucuronic acid substitutions on the xylan during the bulk delignification phase. An important finding is that substantial xylan is still present in the liquor without degradation. Cellulose hydrolysis yields in the range of 80 to 90 % were achievable within 24–48 h for the diverse hardwoods subjected to delignification by alkali at modest enzyme loadings. It was found that substantial delignification was not necessary to achieve these high hydrolysis yields and that hybrid poplar subjected to pretreatment removing only 46 % of the lignin was capable of reaching yields comparable to hybrid poplar pretreated to 67 or 86 % lignin removal. Decreasing the lignin content was found to increase the initial rate of cellulose hydrolysis to glucose while lignin contents under approximately 70 mg/g original biomass were found to slightly decrease the maximum extent of hydrolysis, presumably due to drying-induced cellulose aggregation and pore collapse. Pretreatments were performed on woodchips, which necessitated a “disintegration” step following pretreatment. This allowed the effect of comminution method to be investigated for the three hardwoods subjected to the highest level of delignification. It was found that additional knife-milling following distintegration did not impact either the rate or extent of glucan and xylan hydrolysis.

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Identification of features associated with plant cell wall recalcitrance to pretreatment by alkaline hydrogen peroxide in diverse bioenergy feedstocks using glycome profiling.

Li, M., Pattathil, S., Hahn, M. G. & Hodge, D. B. (2014). RSC Advances, 4(33), 17282-17292.

A woody dicot (hybrid poplar), an herbaceous dicot (goldenrod), and a graminaceous monocot (corn stover) were subjected to alkaline hydrogen peroxide (AHP) pretreatment and subsequent enzymatic hydrolysis in order to assess how taxonomically and structurally diverse biomass feedstocks respond to a mild alkaline oxidative pretreatment and how differing features of the cell wall matrix contribute to its recalcitrance. Using glycome profiling, we determined changes in the extractability of non-cellulosic glucans following pretreatment by screening extracts of the pretreated walls with a panel of 155 cell wall glycan-directed monoclonal antibodies to determine differences in the abundance and distribution of non-cellulosic glycan epitopes in these extracts and assess pretreatment-induced changes in the structural integrity of the cell wall. Two taxonomically-dependent outcomes of pretreatment were identified that both improved the subsequent enzymatic hydrolysis yields but differed in their impacts on cell wall structural integrity. Specifically, it was revealed that goldenrod walls exhibited decreases in all classes of alkali-extractable glycans indicating their solubilization during pretreatment, which was accompanied by an improvement in the subsequent extractability of the remaining cell wall glycans. The corn stover walls did not show the same decreases in glycan abundance in extracts following pretreatment, but rather mild increases in all classes of cell wall glycans, indicating overall weaker associations between cell wall polymers and improved extractability. The hybrid poplar walls were relatively unaffected by pretreatment in terms of composition, enzymatic hydrolysis, and the extractability of cell wall glycans due presumably to their higher lignin content and denser vascular structure.

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Dietary Supplementation with Soluble Plantain Non-Starch Polysaccharides Inhibits Intestinal Invasion of Salmonella Typhimurium in the Chicken.

Parsons, B. N., Wigley, P., Simpson, H. L., Williams, J. M., Humphrey, S., Salisbury, A. M., Watson, A. J., Fry, S. C., O'Brien, D., Roberts, C. L., O'Kennedy, N., Keita, Å. V., Söderholm, J. D., Rhodes, J. M. & Campbell, B. J. (2014). PloS One, 9(2), e87658.

Soluble fibres (non-starch polysaccharides, NSP) from edible plants but particularly plantain banana (Musa spp.), have been shown in vitro and ex vivo to prevent various enteric pathogens from adhering to, or translocating across, the human intestinal epithelium, a property that we have termed contrabiotic. Here we report that dietary plantain fibre prevents invasion of the chicken intestinal mucosa by Salmonella. In vivo experiments were performed with chicks fed from hatch on a pellet diet containing soluble plantain NSP (0 to 200 mg/d) and orally infected with S.Typhimurium 4/74 at 8 d of age. Birds were sacrificed 3, 6 and 10 d post-infection. Bacteria were enumerated from liver, spleen and caecal contents. In vitro studies were performed using chicken caecal crypts and porcine intestinal epithelial cells infected with Salmonella enterica serovars following pre-treatment separately with soluble plantain NSP and acidic or neutral polysaccharide fractions of plantain NSP, each compared with saline vehicle. Bacterial adherence and invasion were assessed by gentamicin protection assay. In vivo dietary supplementation with plantain NSP 50 mg/d reduced invasion by S.Typhimurium, as reflected by viable bacterial counts from splenic tissue, by 98.9% (95% CI, 98.1–99.7; P <0.0001). In vitro studies confirmed that plantain NSP (5–10 mg/ml) inhibited adhesion of S.Typhimurium 4/74 to a porcine epithelial cell-line (73% mean inhibition (95% CI, 64–81); P <0.001) and to primary chick caecal crypts (82% mean inhibition (95% CI, 75–90); P <0.001). Adherence inhibition was shown to be mediated via an effect on the epithelial cells and Ussing chamber experiments with ex-vivo human ileal mucosa showed that this effect was associated with increased short circuit current but no change in electrical resistance. The inhibitory activity of plantain NSP lay mainly within the acidic/pectic (homogalacturonan-rich) component. Supplementation of chick feed with plantain NSP was well tolerated and shows promise as a simple approach for reducing invasive salmonellosis.

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Optimization of a formic/acetic acid delignification treatment on beech wood and its influence on the structural characteristics of the extracted lignins.

Simon, M., Brostaux, Y., Vanderghem, C., Jourez, B., Paquot, M. & Richel, A. (2014). Journal of Chemical Technology and Biotechnology, 89(1), 128-136.

Background: In order to replace petrochemicals by bio-based lignin products in high value-added applications, a formic/acetic acid treatment was adapted to beech wood (Fagus sylvatica L.) for lignin extraction. Results: Beech wood particles were delignified at atmospheric pressure by a formic acid/acetic acid/water mixture. Cooking time and temperature were optimized for delignification, pulp yield and 2-furfural concentration. Response surface design analysis revealed that delignification yield increased with cooking time and temperature. Conclusion: The multi-criteria optimization of delignification was used to find the ideal cooking conditions (5 h 07 min, 104.2°C) to maximize delignification (70.5%) and pulp yield (58.7%) and, to a lesser extent, minimize 2-furfural production. Treatment conditions were found to influence the chemical structure of extracted lignins. Cooking time and temperature inversely influenced lignin molecular weights.

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Correlating lignin structural features to phase partitioning behavior in a novel aqueous fractionation of softwood Kraft black liquor.

Stoklosa, R. J., Velez, J., Kelkar, S., Saffron, C. M., Thies, M. C. & Hodge, D. B. (2013). Green Chemistry, 15(10), 2904-2912.

In this work, a set of softwood lignins were recovered from a Kraft black liquor using a novel pH-based fractionation process involving sequential CO2 acidification and separation of the solvated aqueous lignin fraction. These recovered lignins fractions were characterized with respect to properties that may be responsible for their phase partitioning behavior as well as properties that may render the lignins more suitable for materials applications. Lignin fractions were recovered between a pH range of 12.8 and 9.5 with the bulk of the lignin (90%) recovered between a pH of 11.1 and 10.0. While all the fractions were found to consist primarily of lignin as validated by sample methoxyl content, the first fractions to phase separated were found to be especially enriched in aliphatic extractives and polysaccharides. From the bulk of the lignin that was recovered between a pH of 11.1 and 10.0 a number of noteworthy trends were discernible from the data. Specifically, the phenolic hydroxyl content was found to exhibit a strong negative correlation to the fractionation pH and exhibited a nearly 50% increase with recovery at decreasing pH, while the GPC-estimated molecular weights and 13C NMR-estimated β-O-4 content showed strong positive correlations to the pH at recovery. The aliphatic hydroxyl content exhibited minimal differences between recovery conditions. Overall, these results suggest that this fractionation approach can generate lignin fractions enriched in select physical or structural properties that may be important for their application as feedstocks for renewable chemicals or materials.

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Safety Information
Symbol : GHS05, GHS08
Signal Word : Danger
Hazard Statements : H315, H318, H360
Precautionary Statements : P201, P202, P264, P280, P302+P352, P305+P351+P338, P308+P313, P310, P405, P501
Safety Data Sheet
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