The structure of galactoglucomannan impacts the degradation under alkaline conditions

Abstract

Galactoglucomannan (GGM) from spruce was studied with respect to the degradation behavior in alkaline solution. Three reference systems including galactomannan from locust bean gum, glucomannan from konjac and the linear water-soluble carboxymethyl cellulose were studied with focus on molecular weight, sugar composition, degradation products, as well as formed oligomers, to identify relative structural changes in GGM. Initially all mannan polysaccharides showed a fast decrease in the molecular weight, which became stable in the later stage. The degradation of the mannan polysaccharides could be described by a function corresponding to the sum of two first order reactions; one slow that was ascribed to peeling, and one fast that was connected with hydrolysis. The galactose side group was stable under conditions used in this study (150 min, 90°C, 0.5 M NaOH). This could suggest that, apart from the covalent connection to C6 in mannose, the galactose substitutions also interact non-covalently with the backbone to stabilize the structure against degradation. Additionally, the combination of different backbone sugars seems to affect the stability of the polysaccharides. For carboxymethyl cellulose the degradation was linear over time which further suggests that the structure and sugar composition play an important role for the alkaline degradation. Molecular dynamics simulations gave details about the conformational behavior of GGM oligomers in water solution, as well as interaction between the oligomers and hydroxide ions.

Centrifugal fractionation of softwood extracts improves the biorefinery workflow and yields functional emulsifiers

“…The signals were tentatively identified based on existing data. [59][60][61] In general, the structure of lignin in CUP is consistent with the previously published HSQC spectrum of milled wood lignin. 61 The signals for the main carbohydrates in GGM were also found, and the result of NMR analysis was comparable to that of the quantitative analysis of monosaccharides.…”

On the interaction of softwood hemicellulose with cellulose surfaces in relation to molecular structure and physicochemical properties of hemicellulose

“…The proton NMR resonances in the anomeric region were assigned based on HSQC and confirmed by comparison with literature. 18,19,[59][60][61] The spectra recorded for both samples are similar confirming the similarity of the two samples. Hence, the SP is used as a template to describe assignments of the peaks.…”

Wood hemicelluloses exert distinct biomechanical contributions to cellulose fibrillar networks

“…The distribution between C 2 and C 3 acetylation on extracted hemicelluloses were estimated by 2D heteronuclear single quantum coherence NMR (HSQC NMR) spectroscopy. Approximately 10 mg of sample was dissolved in 700 µl D 2 O and analyzed by the HSQC method for 85 scans 85 . The C 2 and C 3 distribution were estimated form integrating the respective peaks 13,85 .…”

“…Approximately 10 mg of sample was dissolved in 700 µl D 2 O and analyzed by the HSQC method for 85 scans 85 . The C 2 and C 3 distribution were estimated form integrating the respective peaks 13,85 .…”