An investigation of the prebiotic potential and gut health benefits of Irish seaweeds

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Collins, Kenneth G.
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University College Cork
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Seaweeds are an excellent source of biologically active secondary metabolites. Compounds from seaweeds have exhibited a wide range of therapeutic activities and seaweeds have now been proposed as a new source of prebiotics. Firstly, the bifidogenic potential of 15 Irish seaweeds was assessed using in vitro anaerobic fermentations. This investigation suggests that different Bifidobacterium species can utilise seaweed carbohydrates as their sole carbon source for growth, with the greatest bifidogenic activity exhibited by Fucus serratus. Following this, the prebiotic potential of F. serratus was investigated using a faecal fermentation approach. An extract was prepared using a hot-acid extraction followed by ethanol precipitation, size-exclusion dialysis and a simulated gastric digestion. While not all the expected prebiotic markers were met, an increase in the production of SCFA, especially propionate, is a positive outcome for promoting overall gut health and in combating obesity through enhancing satiety. Two similarly processed extracts from the seaweed Laminaria digitata were prepared to study the effect of depolymerisation with hydrogen peroxide on prebiotic potential. Depolymerisation significantly increased propionate production and reduced butyrate production. Modulation of polysaccharide chain length can bring about different fermentation profiles from the same seaweed raw material and starting faecal microbiota. The prebiotic potential of the red seaweed Chondrus crispus was also investigated, however, only a minimal stimulatory effect on the ex vivo microbial population was observed and limited changes in SCFA production. Finally, polyphenol rich extracts from Fucus vesiculosus, F. serratus F. spiralis, Ascophyllum nodosum and Pelvetia canaliculata demonstrated potent activity against Listeria monocytogenes. Greatest activity was observed with F. vesiculosus extracts, which showed activity against several strains of Listeria. Overall this thesis shows that seaweed polysaccharides, especially those from brown seaweeds have great prebiotic potential but the definitive prebiotic test will be to transition to in vivo trials in animals and eventually humans.
Seaweed , Prebiotic , Bifidobacterium , Short-chain fatty acids , Antimicrobial , Depolymerisation , Hot-acid extraction , Microbiota , Dietary fiber
Collins, K. G. 2017. An investigation of the prebiotic potential and gut health benefits of Irish seaweeds. PhD Thesis, University College Cork.
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