Structural analysis of a polysaccharide fromChlorella kessleri by means of gas chromatography—mass spectrometry of its saccharide alditols

Physicochemical characterization, digestion profile and gut microbiota regulation activity of intracellular polysaccharides from Chlorella zofingiensis

A number of studies have shown that the polysaccharides from microalgae exhibit diverse biological activities, however, little is known about their digestibility and impact on human gut microbiota. In this study, a simulating digestion and fermentation system were established to investigate the digestibility and fermentation of intracellular polysaccharides from Chlorella zofingiensis (CZIP-S3). The results indicated that CZIP-S3 is a macromolecular polysaccharide composed of mannose, glucose, galactose and rhamnose, consisting of a main chain and two branched repeating units. CZIP-S3 could not be digested in the upper gastrointestinal tract. However, CZIP-S3 could be metabolized into smaller molecules by the gut microbiota. The pH values continuously decrease during fermentation, whereas, the amount of short-chain fatty acids steadily increase. Furthermore, CZIP-S3 could modulate the composition of gut microbiota, via lowering the ratio of Firmicutes/Bacteroidetes and increasing the relative abundance of Bacteroides, Bifidobacterium and Akkermansia. The data suggested that CZIP-S3 could potentially be used as an ingredient for functional foods or prebiotics to improve human health by promoting the relative abundances of beneficial bacteria.

Extract Methods, Molecular Characteristics, and Bioactivities of Polysaccharide from Alfalfa (Medicago sativa L.)

The polysaccharide isolated from alfalfa was considered to be a kind of macromolecule with some biological activities; however, its molecular structure and effects on immune cells are still unclear. The objectives of this study were to explore the extraction and purifying methods of alfalfa (Medicago sativa L.) polysaccharide (APS) and decipher its composition and molecular characteristics, as well as its activation to lymphocytes. The crude polysaccharides isolated from alfalfa by water extraction and alcohol precipitation methods were purified by semipermeable membrane dialysis. Five batches of alfalfa samples were obtained from five farms (one composite sample per farm) and three replicates were conducted for each sample in determination. The results from ion chromatography (IC) analysis showed that the APS was composed of fucose, arabinose, galactose, glucose, xylose, mannose, galactose, galacturonic acid (GalA), and glucuronic acid (GlcA) with a molar ratio of 2.6:8.0:4.7:21.3:3.2:1.0:74.2:14.9. The weight-average molecular weight (Mw), number-average molecular weight (Mn), and Z-average molecular weight (Mz) of APS were calculated to be 3.30 × 10⁶, 4.06 × 10⁵, and 1.43 × 10⁸ g/mol, respectively, according to the analysis by gel permeation chromatography-refractive index-multiangle laser light scattering (GPC-RI-MALS). The findings of electron ionization mass spectrometry (EI-MS) suggest that APS consists of seven linkage residues, namely 1,5-Araf, galactose (T-D-Glc), glucose (T-D-Gal), 1,4-Gal-Ac, 1,4-Glc, 1,6-Gal, and 1,3,4-GalA, with molar proportions of 10.30%, 4.02%, 10.28%, 52.29%, 17.02%, 3.52%, and 2.57%, respectively. Additionally, APS markedly increased B-cell proliferation and IgM secretion in a dose- and time-dependent manner but not the proliferation and cytokine (IL-2, -4, and IFN-γ) expression of T cells. Taken together, the present results suggest that APS are macromolecular polymers with a molar mass (indicated by Mw) of 3.3 × 10⁶ g/mol and may be a potential candidate as an immunopotentiating pharmaceutical agent or functional food.

Carbonaceous and nitrogenous disinfection by-product formation from algal organic matter

Seasonal algal blooms in drinking water sources release intracellular and extracellular algal organic matter (AOM) in significant concentrations into the water. This organic matter provides precursors for disinfection by-products (DBPs) formed when the water is subsequently chlorinated at the final disinfection stage of the potable water treatment process. This paper presents results of AOM characterisation from five algal species (three cyanobacteria, one diatom and one green) alongside the measurement of the DBP formation potential from the AOM of six algal species (an additional diatom). The character was explored in terms of hydrophilicity, charge and protein and carbohydrate content. 18 DBPs were measured following chlorination of the AOM samples: the four trihalomethanes (THMs), nine haloacetic acids (HAAs), four haloacetonitriles (HANs) and one halonitromethane (HNM). The AOM was found to be mainly hydrophilic (52 and 81%) in nature. Yields of up to 92.4 μg mg^-1 C carbonaceous DBPs were measured, with few consistent trends between DBP formation propensity and either the specific ultraviolet absorbance (SUVA) or the chemical characteristics. The AOM from diatomaceous algae formed significant amounts of nitrogenous DBPs (up to 1.7 μg mg^-1 C). The weak trends in DBPFP may be attributable to the hydrophilic nature of AOM, which also makes it more challenging to remove by conventional water treatment processes.

Algae as nutritional and functional food sources: revisiting our understanding

Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.

Structural, thermal, and anti-inflammatory properties of a novel pectic polysaccharide from alfalfa (Medicago sativa L.) stem

A pectic polysaccharide (APPS) was purified from the cold alkali extract of alfalfa stem and characterized to be a rhamnogalacturonan I (RG-I) type pectin with the molecular weight of 2.38 × 10(3) kDa and a radius of 123 nm. The primary structural analysis indicated that APPS composed of a →2)-α-l-Rhap-(1→4)-α-d-GalpA-(1→ backbone with 12% branching point at C-4 of Rhap forming side chains by l-arabinosyl and d-galactosyl oligosaccharide units. Transmission electron microscopy (TEM) analysis revealed a primary linear-shaped structure with a few branches in its assembly microstructures. The thermal decomposition evaluation revealed the stability of APPS with an apparent activation energy (Ea) of 226.5 kJ/mol and a pre-exponential factor (A) of 2.10 × 10(25)/s, whereas its primary degradation occurred in the temperature range from 215.6 to 328.0 °C. In addition, APPS showed significant anti-inflammatory effect against mRNA expressions of the pro-inflammatory cytokine genes, especially for IL-1β, suggesting its potential utilization in functional foods and dietary supplement products.

A novel alkaline hemicellulosic heteroxylan isolated from alfalfa (Medicago sativa L.) stem and its thermal and anti-inflammatory properties

A novel hemicellulosic polysaccharide (ACAP) was purified from the cold alkali extraction of alfalfa stems and characterized as a heteroxylan with a weight-average molecular weight of 7.94 × 10(3) kDa and a radius of 58 nm. Structural analysis indicated that ACAP consisted of a 1,4-linked β-D-Xylp backbone with 4-O-MeGlcpA and T-L-Araf substitutions at O-2 and O-3 positions, respectively. Transmission electron microscopy (TEM) examination revealed the entangled chain morphology of ACAP molecules. The evaluation of thermal degradation property revealed a primary decomposition temperature range of 238.8-314.0 °C with an apparent activation energy (Ea) and a pre-exponential factor (A) of 220.0 kJ/mol and 2.81 × 10(24)/s, respectively. ACAP also showed significant inhibitory activities on IL-1β, IL-6, and COX-2 gene expressions in cultured RAW 264.7 mouse macrophage cells. These results suggested the potential utilization of ACAP in functional foods and dietary supplement products.

Derivatization of carbohydrates for GC and GC-MS analyses

GC and GC-MS are excellent techniques for the analysis of carbohydrates; nevertheless the preparation of adequate derivatives is necessary. The different functional groups that can be found and the diversity of samples require specific methods. This review aims to collect the most important methodologies currently used, either published as new procedures or as new applications, for the analysis of carbohydrates. A high diversity of compounds with diverse functionalities has been selected: neutral carbohydrates (saccharides and polyalcohols), sugar acids, amino and iminosugars, polysaccharides, glycosides, glycoconjugates, anhydrosugars, difructose anhydrides and products resulting of Maillard reaction (osuloses, Amadori compounds). Chiral analysis has also been considered, describing the use of diastereomers and derivatives to be eluted on chiral stationary phases.