Molecular, rheological and physicochemical characterisation of puka gum, an arabinogalactan-protein extracted from the Meryta sinclairii tree

Functional Properties, Rheological Characteristics, Simulated Digestion, and Fermentation by Human Fecal Microbiota of Polysaccharide from Morchella importuna

Morchella importuna polysaccharide (MIP) has been proven to have obvious hypoglycemic effects on mice with type 2 diabetes (T2DM). This study looked at the functional and rheological characteristics of MIP, and investigated the effects of MIP on the human fecal microbiota through in vitro fermentation experiments. The outcomes demonstrate the excellent oil-holding capacity, emulsifying, foaming, and rheological characteristics of MIP. After salivary gastrointestinal digestion, the Mw of MIP decreased from 398.2 kDa and 21.5 kDa to 21.9 kDa and 11.7 kDa. By 16S rRNA sequencing of bacteria fermented in vitro, it was found that MIP did not improve the richness and diversity of intestinal microorganisms, but it may exert an anti-T2DM function by significantly increasing the relative abundance of Firmicutes and promoting Ruminococcaceae_UCG_014, Bacteroides, and Blautia proliferation. Escherichia-Shigella could also be inhibited to improve the intestinal microenvironment. In addition, the fermentation of MIP increased the total short-chain fatty acid (SCFA) concentration from 3.23 mmol/L to 39.12 mmol/L, and the propionic acid content increased significantly. In summary, MIP has excellent processing performance and is expected to exert potential anti-T2DM activity through the human intestinal microbiota, which has broad market prospects.

Use of Raw Peach Gum as a Sustainable Additive for the Development of Water-Sensitive and Biodegradable Thermoplastic Starch Films

In this study, formulations of thermoplastic starch (TPS) with 5, 10, and 15 parts per hundred resin (phr) of raw peach gum (PG) were prepared by melt extrusion followed by injection molding to obtain standard specimens for characterization. In addition, biodegradable films were developed by compression molding. It was determined that TPS with 5 phr and 10 phr of PG presented similar mechanical behavior to pure TPS after the processing. However, results indicated that adding PG in 10 phr slowed down the starch's retrogradation, delaying the TPS structure's stiffening. Moreover, the TPS-PG formulations presented improved solubility, which increased by 24% with 10 and 15 phr of PG compared to that shown for TPS. Additionally, PG enhanced the compostability of TPS, causing the sample to disintegrate in a shorter period. In conclusion, it was determined that raw PG added in 10 phr could be added as a sustainable additive to modify the biodegradation and water sensitivity of TPS without affecting its mechanical behavior after processing and delaying the retrogradation of the TPS structure, increasing its shelf life.

Plant type II arabinogalactan: Structural features and modification to increase functionality

Type II arabinogalactans (AGs) are a highly diverse class of plant polysaccharides generally encountered as the carbohydrate moieties of certain extracellular proteoglycans, the so-called arabinogalactan-proteins (AGPs), which are found on plasma membranes and in cell walls. The basic structure of type II AG is a 1,3-β-D-galactan main chain with 1,6-β-D-galactan side chains. The side chains are further decorated with other sugars such as α-l-arabinose and β-d-glucuronic acid. In addition, AGs with 1,6-β-D-galactan as the main chain, which are designated as 'type II related AG' in this review, can also be found in several plants. Due to their diverse and heterogenous features, the determination of carbohydrate structures of type II and type II related AGs is not easy. On the other hand, these complex AGs are scientifically and commercially attractive materials whose structures can be modified by chemical and biochemical approaches for specific purposes. In the current review, what is known about the chemical structures of type II and type II related AGs from different plant sources is outlined. After that, structural analysis techniques are considered and compared. Finally, structural modifications that enhance or alter functionality are highlighted.

Rheological and microstructural properties of polysaccharide obtained from the gelatinous Tremella fuciformis fungus

The gelatinous feature of Tremella fuciformis polysaccharide (TFP) has attracted growing interest in its application as a thickening agent in the food industry. This study aims to reveal the microstructure and rheological properties of TFP. Results showed that TFP randomly distributed in aqueous solutions in an irregular worm-like morphology and formed a more extensive entangled network and stiffer chains at higher concentration solutions. The further rheological study indicated that the TFP solutions exhibited a shear-thinning behavior. Multiple results of dynamic oscillation tests confirmed the viscoelastic properties of TFP. Frequency sweep data display that TFP solutions exhibit solid-like behavior at high frequencies, showing the oscillatory behavior of entangled polymers. The temperature sweep demonstrated that the rheological behavior of TFP is thermally reversible. These results enriched the understanding of the rheology-microstructure relationship of TFP solution and were beneficial to expanding the application of TFP in food processing.

Potential prebiotic properties of exopolysaccharides produced by a novel Lactobacillus strain, Lactobacillus pentosus YY-112

Exopolysaccharides (EPSs) derived from Lactobacilli have important physiological effects and are commonly used as new prebiotics. We identified and studied a new Lactobacillus strain, YY-112, isolated from waxberry (Myrica rubra). This strain, identified as Lactobacillus pentosus, tolerates acids, bile salts, and artificial digestive fluids. The EPS derived from this strain weighed 5.9 × 10⁴ Da and contained glucose, mannose, glucosamine, galactose, and rhamnose at 62.69 : 85.85 : 2.46 : 2.92 : 1.00 molar ratios. We found that the EPS from this strain increased the ratio of Bacteroidetes to Firmicutes and decreased the relative abundance of Proteobacteria, especially Escherichia-Shigella, when added to a simulated gastrointestinal system in vitro. After analysing the short-chain fatty acids, we found that this EPS promoted the production of acetic acid, propionic acid, and butyric acid, and reduced the ratio of acetic acid to propionic acid. We conclude that Lactobacillus pentosus YY-112 is a potential probiotic strain with EPS that is beneficial for the intestinal microbiota and short-chain fatty acid production.

Plants arabinogalactans: From structures to physico-chemical and biological properties

Arabinogalactans (AGs) are plant heteropolysaccharides with complex structures occasionally attached to proteins (AGPs). AGs in cell matrix of different parts of plant are freely available or chemically bound to pectin rhamnogalactan. Type I with predominantly β-d-(1 → 4)-galactan and type II with β-d-(1 → 3) and/or (1 → 6)-galactan structural backbones construct the two main groups of AGs. In the current review, the chemical structure of AGs is firstly discussed focusing on non-traditional plant sources and not including well known industrial gums. After that, processes for their extraction and purification are considered and finally their techno-functional and biological properties are highlighted. The role of AG structure and function on health advantages such as anti-tumor, antioxidant, anti-ulcer- anti-diabetic and other activites and also the immunomodulatory effects on in-vivo model systems are overviewed.

Effects of concentrations, temperature, pH and co-solutes on the rheological properties of mucilage from Dioscorea opposita Thunb. and its antioxidant activity

The mucilage from Dioscorea opposita (DOM) dispersions presented shear-thinning behaviour that well fitted to the Power Law model. The effects of different concentrations (2%-10% w/v), temperatures (25-80 °C), pH (3.0-9.0), freeze-thaw conditions (thawed at 25 °C and 4 °C), co-salts (KCl and CaCl₂) and co-sugars (sucrose, fructose and mannose) on the rheological properties were investigated. Generally, higher concentrations, neutral pH, Ca²⁺ and sugars increased the viscosity of DOM, while increasing temperature (25-65 °C) had opposite effects. The results suggested that cross-linked networks exist in DOM, and viscosity changes may be related to the ionisation of carboxyl groups, structural changes and enhancement/reduction of molecular interactions. Particularly, Ca²⁺ could interact with uronic acids of two or more polysaccharide molecules, modify the network-structure through cross-linking with carboxyl groups, and enhance the stronger carboxylate-cation²⁺-carboxylate interactions. Therefore, DOM is suitable for food applications as thickening or gelling agents in aqueous solutions.

Purification, structure and conformation characterization of a novel glucogalactan from Anoectochilus roxburghii

Anoectochilus roxburghii (AR) has been used in food, medicine and ornamental industries for a long time. Anion exchange resin was proposed to purify the sub-fraction of water-extracted AR polysaccharide (ARPP-70), and a homogeneous polysaccharide ARPP-70a was obtained. The structural features of ARPP-70a were characterized using gas chromatography-mass spectrometry (GC-MS), nuclear magnetic resonance (NMR) spectroscopy, and high performance size exclusion chromatograph coupled with multi-angle laser light scattering (HPSEC-MALLS). The relative weight average molecular weight for ARPP-70a was determined to be 14.8 kDa, and the molar ratio of glucose to galactose was 1.0:3.2. The structure of ARPP-70a was elucidated to be glucogalactan, with backbone comprising β-1,4-linked Galp and some α-1,4-linked Glcp. The conformation characteristics of ARPP-70a were supposed to exist as a random coil chain in 0.1 M NaNO₃ solution. Moreover, in vitro antioxidant activity assays revealed ARPP-70a exhibited appreciable antioxidant potential. To the best of our knowledge, this is the first study to obtain this type of glucogalactan, and provide systematic information on its structural and conformational properties. This study improved the understanding of the physicochemical characteristics of AR polysaccharide, which is beneficial for its further application in food and medicinal industry.

Polysaccharides from New Zealand Native Plants: A Review of Their Structure, Properties, and Potential Applications

Water-soluble, non-starch polysaccharides from plants are used commercially in a wide range of food and non-food applications. The increasing range of applications for natural polysaccharides means that there is growing demand for plant-derived polysaccharides with different functionalities. The geographical isolation of New Zealand and its unique flora presents opportunities to discover new polysaccharides with novel properties for a range of applications. This review brings together data published since the year 2000 on the composition and structure of exudate gums, mucilages, and storage polysaccharides extracted from New Zealand endemic land plants. The structures and properties of these polysaccharides are compared with the structures of similar polysaccharides from other plants. The current commercial use of these polysaccharides is reviewed and their potential for further exploitation discussed.