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

•2% alginate and laminaran increased the count of caecal Bacteroidetes in ICR mice.•Bacteroidetes acidifaciens was considered alginate-susceptible indigenous bacteria (SIB) of the gut.•Bacteroides intestinalis was considered laminaran-SIB.•Isolated B. acidifaciens fermented alginate and mainly produced succinate.•Isolated B. intestinalis fermented laminaran and mainly produced lactate.