Evaluation of the Antibacterial and Prebiotic Potential of Ascophyllum nodosum and Its Extracts Using Selected Bacterial Members of the Pig Gastrointestinal Microbiota

Abstract

<i>Ascophyllum nodosum</i> and its extracts are promising antibacterial and prebiotic dietary supplements for pigs. The objectives of this study were to evaluate the effects of the increasing concentrations of: (1) two whole biomass samples of <i>A. nodosum</i> with different harvest seasons, February (ANWB-F) and November (ANWB-N), in a weaned pig faecal batch fermentation assay, and (2) <i>A. nodosum</i> extracts produced using four different extraction conditions of a hydrothermal-assisted extraction methodology (ANE1-4) and conventional extraction methods with water (ANWE) and ethanol (ANEE) as solvent in individual pure culture growth assays using a panel of beneficial and pathogenic bacterial strains. In the batch fermentation assay, ANWB-F reduced <i>Bifidobacterium</i> spp. counts (<i>p</i> < 0.05) while ANWB-N increased total bacterial counts and reduced <i>Bifidobacterium</i> spp. and <i>Enterobacteriaceae</i> counts (<i>p</i> < 0.05). Of the ANE1-4, produced from ANWB-F, ANWE and ANEE that were evaluated in the pure culture growth assays, the most interesting extracts were the ANE1 that reduced <i>Salmonella</i> Typhimurium, enterotoxigenic <i>Escherichia coli</i> and <i>B. thermophilum</i> counts and the ANE4 that stimulated <i>B. thermophilum</i> growth (<i>p</i> < 0.05). In conclusion, the extraction method and conditions influenced the bioactivities of the <i>A. nodosum</i> extracts with ANE1 and ANE4 exhibiting distinct antibacterial and prebiotic properties in vitro, respectively, that merit further exploration.