Polysaccharide and phlorotannin-enriched extracts of the brown seaweed Ecklonia radiata influence human gut microbiota and fermentation in vitro

This study aimed to understand the prebiotic potential and contribution of four extract fractions from the brown seaweed Ecklonia radiata. Four seaweed fractions were tested for their digestibility and prebiotic effects using an in vitro anaerobic fermentation system containing human faecal inocula. After 24 h fermentation, three seaweed fractions, except the phlorotannin-enriched fraction (PF), significantly increased (P < 0.05) total short chain fatty acid (SCFA) production (68.9–97.3 μmol mL⁻¹) compared to the negative controls comprising either of a blank (36.3 μmol mL⁻¹) or cellulose (39.7 μmol mL⁻¹). The low molecular weight (MW) polysaccharide-enriched fraction (LPF) stimulated the growth of beneficial bacteria including Bifidobacterium, Lactobacillus, and Clostridium coccoides. The high MW polysaccharide-enriched fraction (HPF) showed the greatest potential for improving gut health as this fraction was not digestible by enzymes present in the small intestine, and induced significantly higher butyric acid production (8.2 μmol mL⁻¹) than the positive control, inulin (2.3 μmol mL⁻¹). These findings further demonstrate that E. radiata-derived polysaccharides have the potential to be used as dietary supplements with gut health benefits, worthy of further in vivo studies.