Among the evaluated materials two hybrids brown midrib bmr sorghum biomass were tested compared to three conventional sorghum biomass hybrids. The lignocellulosic composition of the raw biomass of each genotype, and after acid and alkaline pretreatments was determined for future investigations of improved ethanol yields.
The lignocellulosic composition of the biomass of the bmr hybrid B and B stood out, presenting significantly lower lignin contents 4. The results showed that the acid treatment followed by the alkaline treatment showed the best performance after the enzymatic hydrolysis, supported by the Scanning Electron Microscopy SEM , Fourier Transform Infrared Analysis FTIR , Thermal analysis TG and crystallinity index analyzes that demonstrated the desired structural modification.
Cellulosic ethanol production for the evaluated hybrids ranged from 6, to 11, liters per hectare per cycle of days. This may take some time to load.
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B mur3 has a defective xyloglucan-specific galactosyl transferase for the xylosyl residue nearer the reducing end, and lack of the Gal residue at this position eliminates fucosylation as well, leaving only XXXG and XLXG. In leaves, galactosylation at the second position is greatly enhanced Madson et al. Xyloglucan nomenclature is given in Table 1. Determination of xyloglucan oligomer sequence by electrospray-ionization ESI mass spectrometry.
Masses diagnostic of additions of one and two galactose units and one fucose unit are detected in the oligomers from xyloglucan from wild-type Arabidopsis A , whereas mur3 has only a single galactose addition B. A collection of trapped ions can be fragmented further to gain information on the positions of individual sugars in the oligomer. See Table 1 for xyloglucan nomenclature.
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In addition to characterizing alterations to xyloglucan oligomeric structures of the mur2 and mur3 mutants, this method also revealed acetylation of Gal residues of xyloglucans Lerouxel et al. Matrix-assisted laser-desorption ionization mass spectrometry to analyse acetylation patterns on xyloglucan.source url
The polymeric ions are differentially accelerated in the mass spectrometer, and molecular masses as great as kDa are detected by the time interval between laser bombardment and contact with the mass spectrometer anode. The asterisk indicates the respective acetylated xyloglucan fragments. Rapid structural phenotyping of plant cell wall mutants by enzymatic oligosaccharide fingerprinting.
GAXs are the principal cross-linking glycans of grasses and other commelinid monocots, but are found with quite varied degrees of substitution in primary and secondary walls of all angiosperms Carpita and Gibeaut, Several mutants have been characterized for which xylan synthesis and side group substitution are impaired. These findings and others led York and O'Neill to propose a two-step model whereby the short xylan chains seen in irx9 are stitched together after cleavage of the tetrasaccharide, leaving a single tetrasaccharide at the reducing end of the elongated polymer.
Curiously, transcript profiling and heterologous expression of the family 47 retaining glycosyl transferase homologous to IRX10 indicate that these may, in fact, be xylosyl transferases involved in chain lengthening Jensen et al. This observation needs to be reconciled with studies of heterologous expression and in vitro xylan synthase reactions show that both IRX9 and IRX14 are required for xylan synthesis Lee et al.
Characterization of the Cellulosic Cell Wall - Semantic Scholar
Whereas Xyl residues are attached at the O -6 of the glucosyl residues of the xyloglucan backbone, the GlcA side groups are attached at the O -2 of the xylan backbone, respectively, creating greater steric hindrance to hydrolysis of the xylan chain close to the branch point residues. Acetylation of the xylosyl residues places an additional constraint on enzymatic hydrolysis.
Nevertheless, a toolkit of several types of xylan-modifying enzymes has permitted hydrolysis of the xylan backbone in different ways depending on the side group substitution, each giving characteristic profiles. These digestion profiles reveal alterations in side group substitution patterns resulting from mutation. PACE after xylanase digestion showed that mutants of two additional family GT8 members, called gux1 and gux2 , were particularly deficient in xylan oligosaccharides containing GlcA and Me-GlcA, and a double mutant was essentially devoid of all GlcA side groups Mortimer et al.
Bromley et al. In contrast, analysis of gux2 showed that GUX1 has a strong preference to substitute for evenly spaced xylosyl residues, with a majority spaced at DP8 or longer. A growing repertory of xylanase enzymes with differing substituent specificities is already a valuable resource to characterize additional mutants. Li et al. The advantage of this system is the high throughput afforded by the well plate format capability.
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Capillary electrophoresis CE reverals substitution patterns of glucuronoxylans. A charged fluorescent dye is coupled to the reducing end of uronide or neutral oligosaccharides to give electrophoretic mobility and a sensitive means of detection.
In this example, Arabidopsis secondary wall glucuronoxylans were digested into a ladder of oligosaccharides with a xylanase that requires a GlcA side group residue for activity. Quantitation of the fluorescence of each oligomer gives the relative abundance of each oligomer. CE showed that two xylan-specific GlcA transferases had distinctly different patterns of decoration.
GUX1 and GUX2 glucuronyltransferases decorate distinct domains of glucuronoxylan with different substitution patterns. The Plant Journal 74, — Elucidation of the GlcA Me-GlcA side group substitution patterns required de-acetylation of the xylans. However, acetylation represents a substantial amount of the side group substitution of GAX and glucuronoxylans.
Four Arabidopsis reduced wall acetylation genes are expressed during secondary wall formation Lee et al. A quadruple mutant was required to demonstrate significant lowering of acetylation of xylans as determined by 1 H-NMR of xylo-oligosaccharides produced by xylanase. Although these data suggest a redundancy of function, combinatorial double and triple mutants of these four genes suggest that, like GUX1 and GUX2, each might produce a different spacing of acetates along the backbone, and the level of acetylation by one enzyme might vary depending on the activities of the other three Manabe et al.
Partly acetylated Me -GlcA xylo-oligomers of DP3—6 and up to six acetate substitutions resulted from GH10 endoxylanase digestion, and these were quantified by MALDI-TOF; PCA showed different combinations of double mutants could vary from the wild type, and a triple mutant gave an unexpected increased acetylation of certain oligomers and decreased acetylated of others Manabe et al. Using two xylanases with differing activities in the gux1gux2 mutant [without Me -GlcA residues], Busse-Wiche et al.
The complexity of side group substitution of monosaccharides, polysaccharides, and acetylation of uronic acid-rich polysaccharides and their methyl esters represents a major challenge for structural characterization Ralet et al. Mass spectrometry for pectin structure analysis.
Carbohydrate Research , —, Copyright , with permission from Elsevier.