Wood-derived dietary fibers promote beneficial human gut microbiota

Woody biomass is a sustainable and virtually unlimited source of hemicellulosic polysaccharides. The predominant hemicelluloses in softwood and hardwood are galactoglucomannan (GGM) and arabinoglucuronoxylan (AGX), respectively. Based on the structure similarity with common dietary fibers, GGM and AGX may be postulated to have prebiotic properties, conferring a health benefit on the host through specific modulation of the gut microbiota. In this study, we evaluated the prebiotic potential of acetylated GGM (AcGGM) and highly acetylated AGX (AcAGX) obtained from Norwegian lignocellulosic feedstocks in vitro. In pure culture, both substrates selectively promoted the growth of Bifidobacterium, Lactobacillus, and Bacteroides species in a manner consistent with the presence of genetic loci for the utilization of β-manno-oligosaccharides/β-mannans and xylo-oligosaccharides/xylans. The prebiotic potential of AcGGM and AcAGX was further assessed in a pH-controlled batch culture fermentation system inoculated with healthy adult human feces. Results were compared with those obtained with a commercial fructo-oligosaccharide (FOS) mixture. Similarly to FOS, both substrates significantly increased (P < 0.05) the Bifidobacterium population. Other bacterial groups enumerated were unaffected with the exception of an increase in the growth of members of the Bacteroides-Prevotella group, Faecalibacterium prausnitzii, and clostridial cluster IX (P < 0.05). Compared to the other substrates, AcGGM promoted butyrogenic fermentation whereas AcAGX was more propiogenic. Although further in vivo confirmation is necessary, these results demonstrate that both AcGGM and AcAGX from lignocellulosic feedstocks can be used to direct the promotion of beneficial bacteria, thus exhibiting a promising prebiotic ability to improve or restore gut health

Monoclonal antibodies indicate low-abundance links between heteroxylan and other glycans of plant cell walls.

The derivation of two sensitive monoclonal antibodies directed to heteroxylan cell wall polysaccharide preparations has allowed the identification of potential inter-linkages between xylan and pectin in potato tuber cell walls and also between xylan and arabinogalactan-proteins in oat grain cell walls. Plant cell walls are complex composites of structurally distinct glycans that are poorly understood in terms of both in muro inter-linkages and developmental functions. Monoclonal antibodies (MAbs) are versatile tools that can detect cell wall glycans with high sensitivity through the specific recognition of oligosaccharide structures. The isolation of two novel MAbs, LM27 and LM28, directed to heteroxylan, subsequent to immunisation with a potato cell wall fraction enriched in rhamnogalacturonan-I (RG-I) oligosaccharides, is described. LM27 binds strongly to heteroxylan preparations from grass cell walls and LM28 binds to a glucuronosyl-containing epitope widely present in heteroxylans. Evidence is presented suggesting that in potato tuber cell walls, some glucuronoxylan may be linked to pectic macromolecules. Evidence is also presented that suggests in oat spelt xylan both the LM27 and LM28 epitopes are linked to arabinogalactan-proteins as tracked by the LM2 arabinogalactan-protein epitope. This work extends knowledge of the potential occurrence of inter-glycan links within plant cell walls and describes molecular tools for the further analysis of such links.This work was supported by the European Union Seventh Framework Programme (FP7 2007-2013) under the WallTraC project (Grant Agreement number 263916). (This article reflects the authors’ views only and the European Union is not liable for any use that may be made of the information contained herein). The work was also supported by the United Kingdom Biotechnology and Biological Research Council (BBSRC, Grant BB/K017489/1). JX acknowledges support from the Chinese Scholarship Council, TAT from a BBSRC studentship and MGR from the Danish Strategic Research Council and The Danish Council for Independent Research, Technology and Production Sciences as part of the GlycAct project (FI 10-093465). We acknowledge kind gifts of enzymes from Harry Gilbert and oligosaccharides from Sanna Koutaniemi. We thank Theodora Tryfona for mass spectrometry analysis.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00425-015-2375-

Pectin at the oil-water interface: Relationship of molecular composition and structure to functionality

The present review examines how macromolecular structure and functional groups of pectin affect its functionality with particular focus on its interfacial activity. We venture into a description of the particularly complex pectin structure and describe the major building blocks and their properties. In the following section, the role of each structural parameter is discussed with particular attention to protein, degree of acetylation and methylation, molecular weight, and branching. Finally, we discuss how modification of the extraction conditions could be tailored to obtain pectin with the desired emulsification properties. It is proposed that pectin with protein content in the range of 3%, with degree of acetylation greater than 10%, molecular weight between 100 and 200 x103 g mol-1 and enriched in RG-I segments is more likely to perform well as an emulsifier. To tailor such a structure, an aqueous extraction protocol with low pH values (between 2.5-3.5) with a strong monoprotic acid (e.g., HCl) and one-step solvent precipitation should be selected. The proposed set of extraction conditions could be used as a first step towards rational design of pectin with desirable interfacial functionality

Secondary lactic acid bacteria fermentation with wood-derived xylooligosaccharides as a tool to expedite sour beer production

acceptedVersio

New insight into fine structure of red wine RGII

National audienc