In vitro fermentability of xylo-oligosaccharide and xylo-polysaccharide fractions with different molecular weights by human faecal bacteria

Xylo-oligosaccharides and xylo-polysaccharides (XOS, XPS) produced by autohydrolysis of the fibre from oil palm empty fruit bunches (OPEFB) were purified using gel filtration chromatography to separate the XOS and XPS from the crude autohydrolysis liquor. Six mixed fractions of refined XOS and XPS with average degree of polymerisation (avDP) of 4-64 were obtained. These were characterised in terms of their composition and size by HPLC, MALDI-ToF-MS (selected fractions) and carbohydrate gel electrophoresis (PACE). They were assessed in batch culture fermentations using faecal inocula to determine their ability to modulate the human faecal microbiota in vitro by measuring the bacterial growth, organic acid production and the XOS assimilation profile. The gut microbiota was able to utilise all the substrates and there was a link between the XOS/XPS degree of polymerisation with the fermentation properties. In general, XOS/XPS preparations of lower avDP promote better Bifidobacterium growth and organic acid production

Development and characterisation of protein films derived from dried distillers’ grains with solubles and in-process samples

Polymer films were developed utilising proteins extracted from wheat distillers’ dried grains with solubles (DDGS) and in-process samples (wet solids), both by-products of bioethanol production process. Structural characterisation of DDGS and wet solids films indicated a change in the secondary structure of the proteins, reflecting the impact of DDGS production process such as effect of enzyme on protein properties and consequently on the film properties; whereas the developed films exhibited a rough surface with voids. Determination of moisture sensitivity indicated that DDGS films exhibited more hydrophilicity than wet solids films, with the same trend being observed for their water solubility and water uptake. The moisture content and solubility of DDGS films ranged from 10.2-14.2 % and 32.3-41.8 % respectively whereas those for wet solids’ film ranged from 18.9-19.8 % and 23.8-24.2 % respectively. The mechanical properties of DDGS and wet solids (ranging from 0.27-0.32 MPa) were comparatively lower than commercial wheat gluten film (0.6 MPa). The poor mechanical properties and high water vapour permeability of DDGS and the wet solids films limit their application as biodegradable packaging materials. However, based on their hydrophilicity, the developed films have potential applications in agriculture and horticulture as controlled release matrices and soil conditioners

Evaluation of the prebiotic potential of arabinoxylans extracted from wheat distillers’ dried grains with solubles (DDGS) and in-process samples

Distillers’ dried grains with solubles (DDGS) is a low value agro-industrial by-product, rich in arabinoxylans (AX), which is produced by commercial distillery and bioethanol plants. In a first approach, we investigated the prebiotic potential of four fractions comprising arabinoxylan oligosaccharides (AXOS) and xylo-oligosaccharides (XOS) obtained by enzymatic hydrolysis of AX fractions derived from DDGS and wet solids (in-process sample of DDGS production process)s. Anaerobic batch cultures at in controlled pH conditions were used to test the prebiotic activity of the samples. Results did not show significant differences between the enzymatic treatments used and all AXOS/XOS were extensively fermented after 24 h. In addition, significant increases (P<0.05) in Bifidobacterium and total SCFAs were observed after 24 h of fermentation. Finally, DDGS-derived hydrolysates were separated on an anionic semi-preparative column to prepare AXOS/XOS fractions with degree of polymerisation (DP) greater than 3. Bifidogenic activity and an increase of SCFAs were again observed after 24 h of fermentation, although this time the selectivity was higher and the fermentation slower, suggesting that the fermentation of this substrate could take place (at least partially) in the distal part of the colon with highly desirable beneficial effect

Extractability and characteristics of proteins deriving from wheat DDGS

Wheat Distillers’ Dried Grains with Solubles (DDGS) and in-process samples were used for protein extraction. Prolamins were the predominant protein components in the samples. The absence of extractable α- and γ-gliadins in DDGS indicated protein aggregation during the drum drying processing stage. Prolamin extraction was performed using 70% (v/v) ethanol or alkaline-ethanol solution in the presence of reducing agent. DDGS extracts had relatively low protein contents (14-44.9%, w/w), regardless of the condition applied. The wet solids were the most suitable raw material for protein extraction, with recovery yields of ~ 55% (w/w) and protein content of ~58% (w/w) in 70% (v/v) ethanol. Protein extracts from wet solids were significantly rich in glutamic acid and proline. Mass balance calculations demonstrated the high carbohydrate content (~ 50%, w/w) of solid residues. Overall, the feasibility of utilising in-process samples of DDGS for protein extraction with commercial potential was demonstrated

Modified expression of ZmMYB167 in Brachypodium distachyon and Zea mays leads to increased cell wall lignin and phenolic content

One of the challenges to enable targeted modification of lignocellulosic biomass from grasses for improved biofuel and biochemical production lies within our limited understanding of the transcriptional control of secondary cell wall biosynthesis. Here, we investigated the role of the maize MYB transcription factor ZmMYB167 in secondary cell wall biosynthesis and how modified ZmMYB167 expression in two distinct grass model species affects plant biomass and growth phenotypes. Heterologous expression of ZmMYB167 in the C3 model system Brachypodium led to mild dwarf phenotypes, increased lignin (~7% to 13%) and S-lignin monomer (~11% to 16%) content, elevated concentrations of cell wall-bound p-coumaric acid (~15% to 24%) and reduced biomass sugar release (~20%) compared to controls. Overexpression of ZmMYB167 in the C4 model system Zea mays increased lignin (~4% to 13%), p-coumaric acid (~8% to 52%) and ferulic acid (~13% to 38%) content but did not affect plant growth and development nor biomass recalcitrance. Taken together, modifying ZmMYB167 expression represents a target to alter lignin and phenolic content in grasses. The ZmMYB167 expression-induced discrepancies in plant phenotypic and biomass properties between the two grass model systems highlight the challenges and opportunities for MYB transcription factor-based genetic engineering approaches of grass biomass

Oat bran, but not its isolated bioactive β-glucans or polyphenols, have a bifidogenic effect in an in vitro fermentation model of the gut microbiota

Wholegrain oats are known to modulate the human gut microbiota and have prebiotic properties (increase the growth of some health-promoting bacterial genera within the colon). Research to date mainly attributes these effects to the fibre content; however, oat is also a rich dietary source of polyphenols, which may contribute to the positive modulation of gut microbiota. In vitro anaerobic batch-culture experiments were performed over 24 h to evaluate the impact of two different doses (1 and 3 % (w/v)) of oat bran, matched concentrations of β-glucan extract or polyphenol mix, on the human faecal microbiota composition using 16S RNA gene sequencing and SCFA analysis. Supplementation with oats increased the abundance of Proteobacteria (P <0·01) at 10 h, Bacteroidetes (P <0·05) at 24 h and concentrations of acetic and propionic acid increased at 10 and 24 h compared with the NC. Fermentation of the 1 % (w/v) oat bran resulted in significant increase in SCFA production at 24 h (86 (sd 27) v. 28 (sd 5) mm; P <0·05) and a bifidogenic effect, increasing the relative abundance of Bifidobacterium unassigned at 10 h and Bifidobacterium adolescentis (P <0·05) at 10 and 24 h compared with NC. Considering the β-glucan treatment induced an increase in the phylum Bacteroidetes at 24 h, it explains the Bacteriodetes effects of oats as a food matrix. The polyphenol mix induced an increase in Enterobacteriaceae family at 24 h. In conclusion, in this study, we found that oats increased bifidobacteria, acetic acid and propionic acid, and this is mediated by the synergy of all oat compounds within the complex food matrix, rather than its main bioactive β-glucan or polyphenols. Thus, oats as a whole food led to the greatest impact on the microbiota

Changes in the arabinoxylan fraction of wheat grain during 1 alcohol production

Laboratory produced DDGS samples were compared with commercial samples from a distillery and a biofuel plant. Changes in structure, solubility and content of arabinoxylan (AX) was determined. The distillation process results in a relative increase of AX content compared to the starting material. The heating and drying processes involved in the production of DDGS lead to an increased solubility and viscosity of water-extractable AX. Production of DDGS results in structural changes to the AX. There is a decrease in 2-and 3-linked arabinose oligosaccharides, that contributes to around a 50% reduction in arabinosylation in DDGS compared with the starting grains. The current study shows that laboratory-scale DDGS provide an accurate representation of the commercial scale and that the AX composition of DDGS is consistently uniform irrespective of starting material. The uniformity of DDGS and thin stillage makes them a good potential source of AX for production of prebiotics or other novel products

Determination of the prebiotic activity of wheat arabinogalactan peptide (AGP) using batch culture fermentation

Purpose To test the prebiotic activity of wheat arabinogalactan-peptide (AGP), which is a soluble dietary fibre composed of arabinogalactan polysaccharide linked to a 15-residue peptide, which accounts for up to 0.4% of the dry weight of wheat flour. Methods The prebiotic activity of AGP prepared from white wheat flour was tested using in-vitro fermentation by colonic bacteria in automated pH controlled anaerobic stirred batch cultures and compared to fructooligosaccharide (FOS) and wheat flour arabinoxylan (AX). Bacterial populations were measured using fluorescence in-situ hybridisation (flow-FISH) and short-chain fatty acid (SCFA) concentrations were measured using HPLC. Results Fermentation of AGP resulted in a significant bifidogenic activity and increased concentrations of SCFAs, mainly acetate after 24 h of fermentation. Conclusions These results were comparable to those obtained with AX and confirm the prebiotic potential of AGP. Furthermore, fermentation of a mixture of AGP and AX was faster compared to the single substrates and more similar to FOS, indicating that combinations of fermentable carbohydrates with different structures are potentially more effective as prebiotics than single substrates