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Valuable Compounds Extraction from Cereal Waste and By-Products
Published in Francisco J. Barba, Elena Roselló-Soto, Mladen Brnčić, Jose M. Lorenzo, Green Extraction and Valorization of By-Products from Food Processing, 2019
Manuel Viuda-Martos, Juana Fernández-López, José Angel Pérez-Álvarez
The hemicellulose in the plants is formed by a very slightly branched structure composed basically of different polysaccharide polymers with a lower degree of polymerization and orientation than the cellulose or lignin may have (Jones et al., 2017). The main function of hemicellulose is to act as a filling agent for cellulose and lignin spaces. In its composition, you can find various sugars mainly glucose, xylose, galactose, arabinose, and mannose (Reddy and Yang, 2005). The main hemicellulose present in cereals and its by-products is arabinoxylan. Arabinoxylan is a hemicellulose comprising of backbone chains of β-(1-4)-linked d-xylopyranosyl residues to which α-l-arabinofuranose units are linked as side chains. Depending on the source from which the arabinoxylans are produced, there will be a significant variation in both the relative quantity as well as the distribution sequence of these structural elements. The main source of arabinoxylans is the bran of various cereals, such as rye, barley, oats, wheat, rice, sorghum, and millet (Izydorczyk and Dexter, 2008).
Structure and Biosynthesis of Hemicelluloses
Published in Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel, Hemicelluloses and Lignin in Biorefineries, 2017
Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel
Hemicelluloses can be divided into four major groups. Their schematic structures are shown in Figures 4.2. and 4.3Xyloglucans have a glucose backbone and xylose-containing branches; they are the predominant hemicelluloses in many primary cell walls.Xylans, which are the most abundant hemicelluloses, include Glucuronoxylans with a xylose backbone and glucuronic acid branches; they are found in the secondary cell walls of dicots.Arabinoxylans with a xylose backbone and arabinose branches; they are found in endosperm walls of cereals.Glucuronoarabinoxylans (GAXs) with a xylose backbone and branches of arabinose and glucuronic acid; they are found in primary walls of commelinid monocots.Mannans include: Pure mannans with a mannose backbone.Glucomannans with a mannose/glucose backbone.Galactomannans with a mannose backbone and galactose branches.Galactoglucomannans with a mannose/glucose backbone and galactose branches.In addition to being well-defined stored reserve material, mannan-based polysaccharides are also found as ubiquitous components of plant cell walls.5–7β-1,3;1,4-glucans, also called mixed-linkage glucans, have interspaced single β-1,3-linkages; they are highly prevalent in grasses.
Guided dietary fibre intake as a means of directing short-chain fatty acid production by the gut microbiota
Published in Journal of the Royal Society of New Zealand, 2020
Much of the dietary fibre in Western diets is derived from intact cereal grain fibres, including wheat bran (which contains arabinoxylans). Jefferson and Adolphus (2019) systematically reviewed the effects of intact cereal grain fibres on the gut microbiota of healthy adults based on the results of 40 studies. In general, increasing the amount of intact cereal grain fibres consumed per day resulted in increased concentrations of SCFAs in the faeces. Resistant starches and AXOS (produced in bread by including endoxylanase enzyme) tend to raise butyrate concentrations in faeces, although whether these increases are biologically meaningful is not clear. For example, a human trial compared the effects of consuming 25 grams of non-starch polysaccharides (NSP) or 25 grams of NSP plus 22 grams of resistant starch (high amylose starches, RS2) per day during a 4-week period in 46 healthy adults. Faecal butyrate concentrations varied among the participants at baseline (3.5–32.6 mmol/kg). In general, acetate, butyrate and total SCFA concentrations were higher when participants consumed RS compared with baseline and NSP diet (average butyrate increase 2.7 mmol/kg), but individual responses varied (McOrist et al. 2011). Similarly, a human trial with 40 healthy adults assessed the impact of consumption of breads containing AXOS. Consumption of AXOS-enriched breads led to increased faecal butyrate, also with an average increase of 2.7 mmol/kg (Walton et al. 2012).