The thick mucus layer of the gut provides a barrier to infiltration of the underlying epithelia by both the normal microbiota and enteric pathogens. Some members of the microbiota utilise mucin glycoproteins as a nutrient source, but a detailed understanding of the mechanisms used to breakdown these complex macromolecules is lacking. Here we describe the discovery and characterisation of endo-acting enzymes from prominent mucin-degrading bacteria that target the polyLacNAc structures within oligosaccharide side chains of both animal and human mucins. These O-glycanases are part of the large and diverse glycoside hydrolase 16 (GH16) family and are often lipoproteins, indicating that they are surface located and thus likely involved in the initial step in mucin breakdown. These data provide a significant advance in our knowledge of the mechanism of mucin breakdown by the normal microbiota. Furthermore, we also demonstrate the potential use of these enzymes as tools to explore changes in O-glycan structure in a number of intestinal disease states.

No abstract

Seaweeds are an underutilised nutritional resource that could not only compliment the current western diet but potentially bring additional health benefits over and above their nutritional value. There are four groups of seaweed algae; green algae (Chlorophyceae), red algae (Rhodophycae), blue-green algae (Cyanophyceae) and brown algae (Phaeophyceae). Seaweeds are rich in bioactive components including polysaccharides and polyphenols. Polysaccharides content, such as fucoidan, laminarin, as well as alginate is generally high in brown seaweeds which are also a source of polyphenols such as phenolic acids, flavonoids, phlorotannin, stilbenes and lignans. These components have been shown to reduce the activity of digestive enzymes, modulating enzymes such as α-amylase, α-glucosidase, pepsin and lipase. This review discusses the effect of several of these components on the digestive processes within the gastrointestinal tract; focusing on the effect of alginate on pancreatic lipase activity and its potential health benefits. Concluding that there is evidence to suggest alginate has the potential to be used as an obesity treatment, however, further in vivo research is required and an effective delivery method for alginate must be designed.

We formulated and characterised two alginate blends for the encapsulation of stevia extract (SE) via ionic gelation through an extrusion technique. Calcium chloride in SE and calcium chloride solutions were assessed as crosslinkers to overcome phenolic losses by diffusion and increase encapsulation efficiency (EE). Regardless of the blend, all stevia-loaded beads exhibited high EE (62.7-101.0%). The size of the beads decreased as EE increased. Fourier transform infrared analysis showed increased hydrogen bonding between SE and alginates, confirming the successful incorporation of SE within the matrix. Untargeted metabolomics profiling identified 479 free and encapsulated polyphenolic compounds. Flavonoids (catechin and luteolin equivalents) were predominant in SE whereas tyrosols and 5-pentadecylresorcinol equivalents were predominant in all bead formulations. Three-common discriminant compounds were exclusive to each blend and were inversely affected by the crosslinking conditions. Both alginate blends have been shown to be feasible as carrier systems of stevia extracts independent of crosslinking conditions.