|Formulation:||In 3.2 M ammonium sulphate|
|Stability:||> 4 years at 4oC|
|Synonyms:||licheninase; (1→3)-(1→4)-beta-D-glucan 4-glucanohydrolase|
|Concentration:||Supplied at ~ 1,000 U/mL|
|Expression:||Purified from Bacillus subtilis|
|Specificity:||Hydrolysis of (1,4)-β-D-glucosidic linkages in β-D-glucans containing (1,3)- and (1,4)-bonds.|
|Specific Activity:||~ 230 U/mg (40oC, pH 6.5 on barley β-glucan)|
|Unit Definition:||One Unit of lichenase activity is defined as the amount of enzyme required to release one µmole of glucose reducing-sugar equivalents per minute from barley β-glucan (10 mg/mL) in sodium phosphate buffer (100mM), pH 6.5 at 40oC.|
|Application examples:||Applications in carbohydrate research and in the food and feeds, brewing and biofuels industries.|
High purity Lichenase (endo-1,3,1,4-β-Glucanase) (Bacillus subtilis) for use in research, biochemical enzyme assays and in vitro diagnostic analysis.
See all purified Carbohydrate Active enZYmes available.
Mangan, D., Liadova, A., Ivory, R. & McCleary, B. V. (2016). Carbohydrate Research, 435, 162-172.
We report herein the development of a novel assay procedure for the measurement of β-glucanase and lichenase (EC 126.96.36.199) in crude enzyme extracts. Two assay formats based on a) a direct cleavage or b) an enzyme coupled substrate were initially investigated. The ‘direct cleavage’ substrate, namely 4,6-O-benzylidene-2-chloro-4-nitrophenyl-β-31-cellotriosyl-β-glucopyranoside (MBG4), was found to be the more generally applicable reagent. This substrate was fully characterised using a crude malt β-glucanase extract, a bacterial lichenase (Bacillus sp.) and a non-specific endo-1,3(4)-β-glucanase from Clostridium thermocellum (EC 188.8.131.52). Standard curves were derived that allow the assay absorbance response to be directly converted to β-glucanase/lichenase activity on barley β-glucan. The specificity of MBG4 was confirmed by analysing the action of competing glycosyl hydrolases that are typically found in malt on the substrate. Manual and automated assay formats were developed for the analysis of a) β-glucanase in malt flour and b) lichenase enzyme extracts and the repeatability of these assays was fully investigated.Hide Abstract
McCleary, B. V. & Codd, R. (1991). Journal of the Science of Food and Agriculture, 55(2), 303-312.
A commercially available enzymic method for the quantitative measurement of (1→3),(1→4)-β-glucan has been simplified to allow analysis of up to 10 grain samples in 70 min or of 100–200 samples by a single operator in a day. These improvements have been achieved with no loss in accuracy or precision and with an increase in reliability. The glucose oxidase/peroxidase reagent has been significantly improved to ensure colour stability for periods of up to 1 h after development. Some problems experienced with the original method have been addressed and resolved, and further experiments to demonstrate the quantitative nature of the assay have been designed and performed.Hide Abstract
McCleary, B. V. & Nurthen, E. (1986). Journal of the Institute of Brewing, 92(2), 168-173.
A method developed for the quantification of (1→3)(1→4)-β-D-glucan in barley flour has been modified to allow its use in the measurement of this component in malt, wort, beer and spent grain. For malt samples, free D-glucose was first removed with aqueous ethanol. Quantification of the polymer in wort and beer samples involved precipitation of the β-glucan with ammonium sulphate followed by washing with aqueous ethanol to remove free D-glucose. Spent grain was lyophilised and milled and then analysed by the method developed for malt. In all cases, the β-glucan was depolymerised with lichenase and the resultant β-gluco-oligosaccharides hydrolysed to D-glucose with β-D-glucosidase. The released D-glucose was then specifically determined using glucose oxidase-peroxidase reagent.Hide Abstract
McCleary, B. V. & Glennie-Holmes, M. (1985). Journal of the Institute of Brewing, 91(5), 285-295.
A simple and quantitative method for the determination of (1→3) (1→4)-β-D-glucan in barley flour and malt is described. The method allows direct analysis of β-glucan in flour and malt slurries. Mixed-linkage β-glucan is specifically depolymerized with a highly purified (1→3) (1→4)-β-D-glucanase (lichenase), from Bacillus subtilis, to tri-, tetra- and higher degree of polymerization (d.p.) oligosaccharides. These oligosaccharides are then specifically and quantitatively hydrolysed to glucose using purified β-D-glucosidase. The glucose is then specifically determined using glucose oxidase/peroxidase reagent. Since barley flours contain only low levels of glucose, and maltosaccharides do not interfere with the assay, removal of low d.p. sugars is not necessary. Blank values are determined for each sample allowing the direct measurement of β-glucan in values are determined for each sample allowing the direct measurement of β-glucan in malt samples. α-Amylase does not interfere with the assay. The method is suitable for the routine analysis of β-glucan in barley samples derived from breeding programs; 50 samples can be analysed by a single operator in a day. Evaluation of the technique on different days has indicated a mean standard error of 0-1 for barley flour samples containing 3-8 and 4-6% (w/w) β-glucan content.Hide Abstract
Characterization of polysaccharides from different species of brown seaweed using saccharide mapping and chromatographic analysis.
Chen, S., Sathuvan, M., Zhang, X., Zhang, W., Tang, S., Liu, Y. & Cheong, K. L. (2021). BMC Chemistry, 15(1), 1-11.
Brown seaweed polysaccharides (BSPs) are one of the primary active components from brown seaweed that has a range of pharmaceutical and biomedical applications. However, the quality control of BSPs is a challenge due to their complicated structure and macromolecule. In this study, saccharide mapping based on high-performance liquid chromatography (HPLC), multi-angle laser light scattering, viscometer, and refractive index detector (HPSEC-MALLS-Vis-RID), and Fourier transform infrared (FT-IR) were used to discriminate the polysaccharides from nine different species of brown algae (BA1-9). The results showed that BSPs were composed of β-D-glucans and β-1,3−1,4-glucan linkages. The molecular weight, radius of gyration, and intrinsic viscosity of BSPs were ranging from 1.718 × 105 Da to 6.630 × 105 Da, 30.2 nm to 51.5 nm, and 360.99 mL/g to 865.52 mL/g, respectively. Moreover, α values of BSPs were in the range of 0.635 to 0.971, which indicated a rigid rod chain conformation. The antioxidant activities of BSPs exhibited substantial radical scavenging activities against DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS (2, 2’-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) radicals, which indicated that the use of BSPs might be a potential approach for antioxidant supplements. Thus, this study gives insights about the structure-function relationship of BSPs, which will be beneficial to improve the quality of polysaccharides derived from marine algae.Hide Abstract
Structural modifications to water-soluble wheat bran arabinoxylan through milling and extrusion.
Demuth, T., Betschart, J. & Nyström, L. (2020). Carbohydrate Polymers, 240, 116328.
Feruloylated arabinoxylan (AX) is one of the most predominant dietary fiber in cereal grains. In recent decades, soluble AX has gained interest, as a result of its well-established health benefits. Apart from enzymatic degradation during cereal storage, food processing causes AX degradation. These reactions lead to structural modifications and influence both the AX functionalities and its health promoting effects. The aim of this study was to investigate the structural modifications and related property changes of health promoting water-extractable (WE) wheat bran AX through grain milling and extrusion. Multi-detector HPSEC revealed a correlation between Mw, conformational changes and the related viscosity behaviour depending on the processing type. Processing caused molecular degradation of insoluble high Mw AX, which increased the solubility significantly. Moreover, extrusion leaded to a more heterogenic AX fine structure. The detailed characterization of processed dietary fiber may help to facilitate the optimized incorporation of AX in health-promoting foods.Hide Abstract
The role of non-starch polysaccharides in determining the air-water interfacial properties of wheat, rye, and oat dough liquor constituents.
Janssen, F., Wouters, A. G., Meeus, Y., Moldenaers, P., Vermant, J. & Delcour, J. A. (2020). Food Hydrocolloids, 105, 105771.
Dough gas cell stability is a prerequisite for obtaining breads with high specific volume and homogeneous crumb. The contribution of cereal endogenous non-starch polysaccharides (NSPs) to gas cell stability during wheat, rye, and oat bread making is still unclear. In this work, the aqueous phases from their fermented doughs were isolated as dough liquor (DL) by ultracentrifugation. The foaming, bulk shear rheology, and air-water (A-W) interfacial properties of wheat and rye DLs (treated with and without endoxylanase) and oat DL (treated with and without both lichenase and β-d-glucosidase) were studied. Enzymatic hydrolysis drastically reduced the apparent bulk shear viscosity of the different DLs and resulted in increased and decreased moduli (or magnitude) of the complex A-W interfacial shear viscosities of wheat and rye DLs, respectively. The latter implies that (non-hydrolyzed) rye DL arabinoxylan strengthens the A-W interfacial film consisting of adsorbed proteins and lipids. No measurable A-W interfacial shear viscosities were obtained for oat DL irrespective of whether its β-D-glucans were hydrolyzed or not. This is probably because lipids dominate the oat DL A-W interfaces. The knowledge generated provides a fundamental basis for specifically modifying the composition of the aqueous phase in wheat, rye, and oat doughs to improve the quality of mixed cereal breads.Hide Abstract
At a high dose even partially degraded beta-glucan with decreased solubility significantly reduced the glycaemic response to bread.
Rieder, A., Knutsen, S. H., Fernandez, A. S. & Ballance, S. (2019). Food & Function, 10(3), 1529-1539.
Cereal beta-glucan can reduce post-prandial glycaemic responses, which makes it an interesting ingredient to improve the health impact of bread, a staple food with a high glycaemic index (GI). Here we compare the ability of different wheat-based breads prepared with oat bran concentrate and barley flour and a Norwegian type of soft wrap (lompe) for their ability to reduce glycaemic responses in healthy adults. Both breads with the highest beta-glucan content (3.8 g per serving) significantly reduced peak blood glucose rise (PBGR), incremental area under the blood glucose curve (iAUC) and GI compared to wheat control regardless of beta-glucan Mw and solubility. At a medium dose of 1.7 g per serving breads with beta-glucan of high MW and solubility significantly lowered iAUC, but not GI or PBGR compared to white bread. In contrast to previous studies, no significant correlation between viscosity after in vitro digestion and any of the glycaemia variables was found. However, the amount of soluble beta-glucan per serving was inversely correlated with GI. Lompe had a similar medium GI (63) than the high dose beta-glucan breads (56 and 64). However, while “lompe” had significantly lower amounts of rapidly digestible starch, no differences in in vitro starch digestion were found between the different breads. Instead, increased local viscosity at the intestinal border (e.g. soluble beta-glucan interacting with the mucus layer), dilution of nutrients (higher water content and serving size) and/or reduced gastric emptying are proposed as potential explanations for the lower glycaemic responses to high dose beta-glucan breads.Hide Abstract
Molecular characterization of water-extractable arabinoxylan from wheat bran and its effect on the heat-induced polymerization of gluten and steamed bread quality.
Wang, P., Hou, C., Zhao, X., Tian, M., Gu, Z. & Yang, R. (2018). Food Hydrocolloids, 87, 570-581.
Enhanced bread quality by water-extractable arabinoxylan (WEAX) depends on its inherent structural features. To clarify the underlying mechanism, the current study prepared WEAX with varied structures via graded ethanol precipitation from wheat bran, and their effects on the steamed bread quality in relation to the heat-induced physicochemical changes of dough components were evaluated. The results showed that WEAX with a lower molecular weight (Mw), higher branched degree and ferulic acid content possessed a superior improved effect on the steamed bread quality. The gelatinization of starch was partially inhibited by WEAX, with a more distinct effect by the lower Mw and higher branched WEAX. However, WEAX suppressed the short-term retrogradation of starch, especially for the higher Mw and lower branched WEAX. Both of the heat-induced polymerization degree and rate of gluten were reduced by WEAX, and these reductions were more evident by the lower Mw and higher branched WEAX. The partial inhibition of gluten polymerization by WEAX contributed substantially to the enlarged loaf volume and softer textural property of steamed bread. The current study can provide a theoretical basis for the exploitation of WEAX as a nutritious and technofunctional dough improver.Hide Abstract
Cell wall changes during the formation of aerenchyma in sugarcane roots.
Leite, D. C. C., Grandis, A., Tavares, E. Q. P., Piovezani, A. R., Pattathil, S., Avci, U., Rossini, A., Cambler, A., De Souza, A. P., Hahn, M. G. & Buckeridge, M. S. (2017). Annals of Botany, 120(5), 693-708.
Background and Aims: Aerenchyma develops in different plant organs and leads to the formation of intercellular spaces that can be used by the plant to transport volatile substances. Little is known about the role of cell walls in this process, although the mechanism of aerenchyma formation is known to involve programmed cell death and some cell wall modifications. We assessed the role that cell wall-related mechanisms might play in the formation of aerenchyma in sugarcane roots. Methods: Sections of roots (5 cm) were subjected to microtomography analysis. These roots were divided into 1-cm segments and subjected to cell wall fractionation. We performed analyses of monosaccharides, oligosaccharides and lignin and glycome profiling. Sections were visualized by immunofluorescence and immunogold labelling using selected monoclonal antibodies against polysaccharide epitopes according to the glycome profiles. Key Results: During aerenchyma formation, gas spaces occupied up to 40 % of the cortex cross-section within the first 5 cm of the root. As some of the cortex cells underwent dissolution of the middle lamellae, leading to cell separation, cell expansion took place along with cell death. Mixed-linkage β-glucan was degraded along with some homogalacturonan and galactan, culminating in the formation of cell wall composites made of xyloglucan, arabinoxylans, cellulose and possibly lignin. Conclusion: The composites formed seem to play a role in the physical–chemical properties of the gas chambers, providing mechanical resistance to forces acting upon the root and at the same time decreasing permeability to gases.Hide Abstract
Dallabernardina, P., Schuhmacher, F., Seeberger, P. H. & Pfrengle, F. (2017). Chemistry-A European Journal, 23(13), 3191-3196.
The mixed-linkage (1→3),(1→4)-d-glucan (MLG) specific glycosyl hydrolase lichenase is an important biochemical tool for the structural characterization of MLGs. It holds potential for application in the brewery, animal feed, and biofuel industries. Several defined MLG oligosaccharides obtained by automated glycan assembly are used to analyze the substrate specificities of Bacillus subtilis lichenase. Two glucose building blocks (BBs), equipped with a temporary fluorenylmethyloxycarbonyl chloride (Fmoc) protecting group in the C-3 or C-4 position, served to assemble different oligosaccharides by using an automated oligosaccharide synthesizer. Light-induced cleavage of the glycan products from the solid support followed by global deprotection provided seven MLG oligosaccharides of different length and connectivity. After incubation of the MLG oligosaccharides with lichenase, the digestion products were analyzed by HPLC-MS. These digestion experiments provided insights into the enzyme's active site that is in line with other recent evidence suggesting that the substrate specificity of lichenases has to be reconsidered. These results demonstrate that synthetic MLG oligosaccharides are useful tools to analyze mixed-linkage β-glucanases.Hide Abstract
Baek, S. C., Ho, T. H., Lee, H. W., Jung, W. K., Gang, H. S., Kang, L. W. & Kim, H. (2017). Applied Microbiology and Biotechnology, 101(10), 4073-4083.
β-1,3-1,4-Glucanase (BGlc8H) from Paenibacillus sp. X4 was mutated by error-prone PCR or truncated using termination primers to improve its enzyme properties. The crystal structure of BGlc8H was determined at a resolution of 1.8 Å to study the possible roles of mutated residues and truncated regions of the enzyme. In mutation experiments, three clones of EP 2-6, 2-10, and 5-28 were finally selected that exhibited higher specific activities than the wild type when measured using their crude extracts. Enzyme variants of BG2-6, BG2-10, and BG5-28 were mutated at two, two, and six amino acid residues, respectively. These enzymes were purified homogeneously by Hi-Trap Q and CHT-II chromatography. Specific activity of BG5-28 was 2.11-fold higher than that of wild-type BGwt, whereas those of BG2-6 and BG2-10 were 0.93- and 1.19-fold that of the wild type, respectively. The optimum pH values and temperatures of the variants were nearly the same as those of BGwt (pH 5.0 and 40°C, respectively). However, the half-life of the enzyme activity and catalytic efficiency (kcat/Km) of BG5-28 were 1.92- and 2.12-fold greater than those of BGwt at 40°C, respectively. The catalytic efficiency of BG5-28 increased to 3.09-fold that of BGwt at 60°C. These increases in the thermostability and catalytic efficiency of BG5-28 might be useful for the hydrolysis of β-glucans to produce fermentable sugars. Of the six mutated residues of BG5-28, five residues were present in mature BGlc8H protein, and two of them were located in the core scaffold of BGlc8H and the remaining three residues were in the substrate-binding pocket forming loop regions. In truncation experiments, three forms of C-terminal truncated BGlc8H were made, which comprised 360, 286, and 215 amino acid residues instead of the 409 residues of the wild type. No enzyme activity was observed for these truncated enzymes, suggesting the complete scaffold of the α6/α6-double-barrel structure is essential for enzyme activity.Hide Abstract
Grundy, M. M. L-., Quint, J., Rieder, A., Balance, S., Dreiss, C. A., Butterworth, P. J. & Ellis, P. R. (2017). Carbohydrate Polymers, 387-397.
Oat mixed-linkage β-glucan has been shown to lower fasting blood cholesterol concentrations due notably to an increase in digesta viscosity in the proximal gut. To exert its action, the polysaccharide has to be released from the food matrix and hydrated. The dissolution kinetics of β-glucan from three oat materials, varying in their structure, composition and degree of processing, was investigated by incubating the oats at 37°C over multiple time points (up to 72 h). The samples were analysed for β-glucan content, weight-average molecular weight and rheological behaviour. Regardless of the materials studied and the processing applied, the solubilisation of β-glucan was not complete. Mechanical and hydrothermal processing led to differences in the viscosity flow curves of the recovered solutions, with the presence of particulates having a marked effect. This study revealed that the structure and processing methods applied to oat materials resulted in varied and complex rheological properties, especially when particulates are present.Hide Abstract
Grundy, M. M. L., Quint, J., Rieder, A., Ballance, S., Dreiss, C. A., Butterworth, P. J. & Ellis, P. R. (2017). Carbohydrate Polymers, 166, 387-397.
Oat β-glucan has been shown to play a positive role in influencing lipid and cholesterol metabolism. However, the mechanisms behind these beneficial effects are not fully understood. The purpose of the current work was to investigate some of the possible mechanisms behind the cholesterol lowering effect of oat β-glucan, and how processing of oat modulates lipolysis. β-Glucan release, and the rate and extent of lipolysis measured in the presence of different sources of oat β-glucan, were investigated during gastrointestinal digestion. Only a fraction of the original β-glucan content was released during digestion. Oat flakes and flour appeared to have a more significant effect on lipolysis than purified β-glucan. These findings show that the positive action of β-glucan is likely to involve complex processes and interactions with the food matrix. This work also highlights the importance of considering the structure and physicochemical properties of foods, and not just the nutrient content.Hide Abstract
De Souza, A. P., Kamei, C. L. A., Torres, A. F., Pattathil, S., Hahn, M. G., Trindade, L. M. & Buckeridge, M. S. (2015). Journal of Experimental Botany, 66(14), 4351-4365.
The production of bioenergy from grasses has been developing quickly during the last decade, with Miscanthus being among the most important choices for production of bioethanol. However, one of the key barriers to producing bioethanol is the lack of information about cell wall structure. Cell walls are thought to display compositional differences that lead to emergence of a very high level of complexity, resulting in great diversity in cell wall architectures. In this work, a set of different techniques was used to access the complexity of cell walls of different genotypes of Miscanthus sinensis in order to understand how they interfere with saccharification efficiency. Three genotypes of M. sinensis displaying different patterns of correlation between lignin content and saccharification efficiency were subjected to cell wall analysis by quantitative/qualitative analytical techniques such as monosaccharide composition, oligosaccharide profiling, and glycome profiling. When saccharification efficiency was correlated negatively with lignin, the structural features of arabinoxylan and xyloglucan were found to contribute positively to hydrolysis. In the absence of such correlation, different types of pectins, and some mannans contributed to saccharification efficiency. Different genotypes of M. sinensis were shown to display distinct interactions among their cell wall components, which seem to influence cell wall hydrolysis.Hide Abstract
Källman, A., Bertoft, E., Koch, K., Sun, C., Åman, P. & Andersson, R. (2015). International Journal of Biological Macromolecules, 81, 730-735.
Barley spikes of the cultivars/breeding lines Gustav, Karmosé and SLU 7 were harvested at 9, 12 and 24 days after flowering in order to study starch structure in developing barley endosperm. Kernel dry weight, starch content and amylose content increased during development. Structural analysis was performed on whole starch and included the chain-length distribution of the whole starches and their β-limit dextrins. Karmosé, possessing the amo1 mutation, had higher amylose content and a lower proportion of long chains (DP ≥38) in the amylopectin component than SLU 7 and Gustav. Structural differences during endosperm development were seen as a decrease in molar proportion of chains of DP 22–37 in whole starch. In β-limit dextrins, the proportion of Bfp-chains (DP 4–7) increased and the proportion of BSmajor-chains (DP 15–27) decreased during development, suggesting more frequent activity of starch branching enzymes at later stages of maturation, resulting in amylopectin with denser structure.Hide Abstract
Gamel, T. H., Abdel-Aal, E. S. M., Ames, N. P., Duss, R., & Tosh, S. M. (2014). Journal of Cereal Science, 59(1), 33-40.
The viscosity of the soluble fibre, β-glucan, has been shown to influence its ability to lower serum cholesterol and postprandial blood glucose levels. The impact of various amylases, proteases and lipase on the solubility and resulting viscosity of β-glucan extracted from oat bran cereals with a range of β-glucan concentrations and molecular weights was investigated. Addition of enzymes increased the final viscosity of high molecular weight β-glucan in cereals by facilitating the release of β-glucan from the food matrix. For cereals with partially depolymerized β-glucan, the addition of digestive enzymes decreased the final viscosity by eliminating the contribution of starch and protein to viscosity. Final viscosity varied depending on enzyme combinations including pancreatin, salivary and microbial α-amylases, microbial protease, porcine protease, trypsin and α-chymotrypsin. Addition of lipase did not significantly affect viscosity or solubility of β-glucan extracted from oat crackers. Addition of lichenase showed that β-glucan was the major contributor of viscosity to the system, with negligible interference from other components. The viscosity of the optimized protocol was compared to physiological results previously obtained. The viscosity of β-glucan extracted with pancreatin plus microbial α-amylase (pH 6.9) was predictive of LDL-cholesterol reduction (R2 = 0.847) and glycemic response (R2 = 0.883).Hide Abstract
Rieder, A., Grimmer, S., Aachmann, F. L., Westereng, B., Kolset, S. O. & Knutsen, S. H. (2013). Carbohydrate Polymers, 92(2), 2075-2083.
Even if carbohydrate preparations from plant/fungal sources have a high degree of purity, observed immune-stimulation may be caused by minute sample contaminations. Using the example of different β-glucans we present a range of analytical tools crucial for validation of possible immune-stimulatory effects. Two yeast (MacroGard and Zymosan) and one cereal β-glucan (CBG40) increased IL-8 secretion by HT-29 cells considerably. Degradation of the β-glucan samples with β-glucan specific enzymes did hardly influence the effect of Zymosan and CBG40 but significantly decreased the effect of MacroGard. Stimulation of IL-8 secretion by CBG40 and Zymosan was hence not due to their β-glucan content. Instead, the effect of the CBG40 sample was due to low levels of LPS despite the inability of the known LPS inhibitor Polymyxin B to supress its stimulatory effect. We conclude that targeted enzymatic degradation of samples is a powerful validation tool to investigate carbohydrate specific immune-modulation.Hide Abstract
Ryu, J. H., Lee, S., You, S., Shim, J. H. & Yoo, S. H. (2012). Carbohydrate Polymers, 89(4), 1238-1243.
In order to understand the relationship between chemical structure and physical properties of cereal β-glucans, the β-glucans with identical Mw (98.4–99.2 kDa) and Rg (21.1–22.0 nm) were isolated from chal and gwangan barley, and ohl oat, and their linkage structure, flow behavior, and thermal properties were investigated. Previously, we established a purification method of 3-O-cellobiosyl-glucose (DP3) and 3-O-cellotriosyl-glucose (DP4) ( Yoo, Lee, Chang, Lee, & Yoo, 2007) and applied these authentic standards to quantify the ratio of β-(1,4)/(1,3) linkages in cereal β-glucans. β-Glucans isolated from two barley cultivars had greater proportion of DP3 than did the oat, and within barley cultivars chal barley β-glucan had significantly larger amount of DP3 over gwangan cultivar. Thus, chal barley β-glucan had the greatest molar ratio (2.53) of DP3 to DP4, and ohl oat had the lowest (1.51). While all the β-glucan solutions showed strong shear thinning behavior, ohl oat β-glucan with higher proportion of DP4 exhibited the highest viscosity among the β-glucan samples. After 3 freeze-thaw cycles of 3% (w/v) β-glucan samples, chal barley β-glucan had lower onset (To) and peak (Tp) temperatures (28.3 and 36.7°C, respectively) than those of gwangan barley (33.6 and 39.9°C) and ohl oat (37.9 and 46.9°C) did, and the heat scan profiles were thermoreversible. The To and Tp of inter-chain associations decreased as the DP3:DP4 ratio of the β-glucan increased. From this study, it was suggested that cellotetraosyl units and longer β-(1,4)-linked segments would be a major contributor for improving solution viscosity and gel formation of cereal β-glucans.Hide Abstract
Identification of quantitative trait loci affecting hemicellulose characteristics based on cell wall composition in a wild and cultivated rice species.
Zhang, S. J., Song, X. Q., Yu, B. S., Zhang, B. C., Sun, C. Q., Knox, J. P. & Zhou, Y. H. (2012). Molecular Plant, 5(1), 162-175.
Cell wall hemicellulosic polysaccharides are structurally complex and diverse. Knowledge about the synthesis of cell wall hemicelluloses and their biological roles is limited. Quantitative trait loci (QTL) mapping is a helpful tool for the dissection of complex phenotypes for gene identification. In this study, we exploited the natural variation in cell wall monosaccharide levels between a common wild rice, Yuanj, and an elite indica cultivar, Teqing, and performed QTL mapping with their introgression lines (ILs). Chemical analyses conducted on the culms of Yuanj and Teqing showed that the major alterations are found in glucose and xylose levels, which are correlated with specific hemicellulosic polymers. Glycosidic linkage examination revealed that, in Yuanj, an increase in glucose content results from a higher level of mixed linkage β-glucan (MLG), whereas a reduction in xylose content reflects a low level of xylan backbone and a varied arabinoxylan (AX) structure. Seventeen QTLs for monosaccharides have been identified through composition analysis of the culm residues of 95 core ILs. Four major QTLs affecting xylose and glucose levels are responsible for 19 and 21% of the phenotypic variance, respectively. This study provides a unique resource for the genetic dissection of rice cell wall formation and remodeling in the vegetative organs.Hide Abstract