Study on the oligosaccharides composition of the water-soluble fraction of marine mucilage by electrospray tandem mass spectrometry

Insights into the bacterial community structure of marine mucilage by metabarcoding

This prospective study was aimed to explore the bacterial diversity of marine mucilage developed in the Marmara Sea and the North Aegean Sea by metabarcoding. For this purpose, mucilage samples were collected from five different sampling locations, and the bacterial community structure was analyzed by 16S rRNA gene amplicon sequencing. The results highlighted a diverse bacterial community dominated by Proteobacteria and Bacteroidetes species. A negative and significant correlation between pH level and Campylobacterales, Clostridiales, and Vibronales abundances was detected, while a strong positive correlation was determined between total phosphorus (TP) and Campylobacterales. Results revealed that the bacterial community in the mucilage samples was predominated by particle-attached species preferring high-nutrient concentrations. This is the first study evaluating the bacterial diversity in a mucilage outbreak using a metabarcoding approach. Its results may contribute to this growing area of research and provide a database for further studies.

Starch-digesting product analysis based on the hydrophilic interaction liquid chromatography coupled mass spectrometry method to evaluate the inhibition of flavonoids on pancreatic α-amylase

An accurate hydrophilic interaction liquid chromatography coupled mass spectrometry (HILIC-MS) method is presented to characterize starch digestion by α-amylase and measure the inhibition properties of flavonoids against α-amylase in vitro. Eleven products were found as 1 → 4 linkage glucose oligosaccharides with different degrees of polymerization (DPs) from 2 to 12. The products with DPs of 2, 3, 6, 7, and 9 had higher yields. The product with DP of 9 had the highest yields, which first increased and then decreased with the reaction time. Pelargonidin has the best inhibition activity on all enzyme products. The 3'-hydroxyl of B-ring enhanced the inhibition activity of flavonol and flavone but weakened that of anthocyanin. The C-ring 3-hydroxyl increased the inhibition effect of flavonol on maltose but decreased that on the products with higher DPs than flavone. The HILIC-MS method can provide more detailed information on enzyme products for the study of flavonoids inhibiting α-amylase.

Chemical composition, nutritive value and health benefits of edible clam Meretrix casta (Chemnitz) from West Coast of India

The present study was undertaken with a view to determine the nutraceutical value of the commonly consumed edible clam, Meretrix casta (Chemnitz), based on the identification of its organic chemical constituents particularly lipids and carbohydrates. Electrospray ionization tandem mass analysis of the bivalve indicated maltodextrins to be the major carbohydrate constituent. Triacylglycerols (TAGs) (0.88%, dry weight) were rich in C14:0, C16:0 to C18:0 (6-11%) saturated and monounsaturated palmitoleic (C16:1n9c; 11.76%) and oleic fatty acids (C18:1n9c; 14.53%). Though the clams contained PUFAs which are known to be beneficial in lowering the risk of cardiovascular diseases, they were devoid of docosahexaenoic acid (C22:6n3). Maltodextrins being less digestible than glucose beneficially affects the host by selectively stimulating the growth of gut microflora particularly Lactobacillus and Bifidobacteria. These microflora inhibit colonization of pathogens by producing butyrate. The profile of sterols (1.67%, dry wt.) showed it to be a complex mixture of C26, C27, C29 and C30. To our knowledge no reports are available in the literature on the identification of maltodextrins and of positional distribution of PUFA's at the sn2 position of TAGs in M. casta. The results of this study demonstrated the positive attributes of the bivalve for human consumption.

Dynamic exchanges between DOM and POM pools in coastal and inland aquatic ecosystems: A review

Dynamic exchanges between dissolved organic matter (DOM) and particulate organic matter (POM) plays a critical role in organic carbon cycling in coastal and inland aquatic ecosystems, interactions with aquatic organisms, mobility and bioavailability of pollutants, among many other ecological and geochemical phenomena. Although DOM-POM exchange processes have been widely studied from different aspects, little to no effort has been made to date to provide a comprehensive, mechanistic, and micro-spatial schema for understanding various exchange processes occurring in different aquatic ecosystems in a unified way. The phenomena occurring between DOM and POM were explained here with the homogeneous and heterogeneous mechanisms. In the homogeneous mechanism, the participating components are only organic matter (OM) constituents themselves with aggregation and dissolution involved, whereas OM is associated with other components such as minerals and particulate colloids in the heterogeneous counterpart. Besides the generally concerned processes of aggregation/dissolution and adsorption/desorption, other ecological factors such as sunlight and organisms can also participate in DOM-POM exchanges through altering the chemical nature of OM. Despite the limitation of current analytical technologies, many unknown and/or unquantified processes need to be identified to unravel the complicated exchanges of OM between its dissolved and particulate states. Based on the review of several previous mathematical models, we proposed a unified conceptual model to describe all major dynamic exchange mechanisms on the basis of exergy theory. More knowledge of dynamic DOM-POM exchanges is warranted to overcome the potential problems arising from a simple division of OM into dissolved versus particulate states and to further develop more sophisticated mathematic models.

Self-assembly of polysaccharides gives rise to distinct mechanical signatures in marine gels

Marine-gel biopolymers were recently visualized at the molecular level using atomic force microscopy (AFM) to reveal fine fibril-forming networks with low to high degrees of cross-linking. In this work, we use force spectroscopy to quantify the intra- and intermolecular forces within the marine-gel network. Combining force measurements, AFM imaging, and the known chemical composition of marine gels allows us to identify the microscopic origins of distinct mechanical responses. At the single-fibril level, we uncover force-extension curves that resemble those of individual polysaccharide fibrils. They exhibit entropic elasticity followed by extensions associated with chair-to-boat transitions specific to the type of polysaccharide at high forces. Surprisingly, a low degree of cross-linking leads to sawtooth patterns that we attribute to the unraveling of polysaccharide entanglements. At a high degree of cross-linking, we observe force plateaus that arise from unzipping, as well as unwinding, of helical bundles. Finally, the complex 3D network structure gives rise to force staircases of increasing height that correspond to the hierarchical peeling of fibrils away from the junction zones. In addition, we show that these diverse mechanical responses also arise in reconstituted polysaccharide gels, which highlights their dominant role in the mechanical architecture of marine gels.

Separation efficiencies in hydrophilic interaction chromatography

Hydrophilic interaction chromatography (HILIC) is important for the separation of highly polar substances including biologically active compounds, such as pharmaceutical drugs, neurotransmitters, nucleosides, nucleotides, amino acids, peptides, proteins, oligosaccharides, carbohydrates, etc. In the HILIC mode separation, aqueous organic solvents are used as mobile phases on more polar stationary phases that consist of bare silica, and silica phases modified with amino, amide, zwitterionic functional group, polyols including saccharides and other polar groups. This review discusses the column efficiency of HILIC materials in relation to solute and stationary phase structures, as well as comparisons between particle-packed and monolithic columns. In addition, a literature review consisting of 2006-2007 data is included, as a follow up to the excellent review by Hemström and Irgum.