Detection and isolation of low molecular weight alginate- and laminaran-susceptible gut indigenous bacteria from ICR mice.

Alginate and laminaran are the main water-soluble polysaccharides in edible brown algae such as arame Eisenia bicyclis. To determine the alginate- and/or laminaran-susceptible indigenous bacteria (SIB) in the gut, the caecal microbiomes of ICR mice fed a diet containing 2% low molecular weight (LMW ≒50 kDa) alginate or laminaran were analysed by 16S rRNA gene (V4) amplicon sequencing. At the phylum level abundances, compared to those in mice fed a no-fibre diet, Firmicutes was lower and Bacteroidetes was higher in both LMW alginate- or laminaran-fed mouse groups. At the operational taxonomic unit level, Bacteroides acidifaciens- and Bacteroides intestinalis-like bacteria were considered alginate- and laminaran-SIB, respectively. B. acidifaciens PS-4 isolated from the ICR mice fermented LMW alginate and laminaran and mainly produced succinate. B. intestinalis ALB-11 also isolated from these mice fermented laminaran and mainly produced lactate. These SIB might exert interactive effects with edible brown algal consumption and affect host health.