Effects of fermented Aphanizomenon flos-aquae on the caecal microbiome of mice fed a high-sucrose and low-dietary fibre diet

Aphanizomenon flos-aquae, a freshwater cyanobacterium harvested from Upper Klamath Lake, Oregon, USA, is employed as a functional food material. Aphanizomenon flos-aquae can be fermented with Lactobacillus plantarum and Lactococcus lactis subsp. lactis. Here, to determine the dietary effects of A. flos-aquae (AFA) and fermented A. flos-aquae (F-AFA) on the mouse gut microbiome, high-sucrose diet containing no dietary fibre (NF), 5% AFA or 5% F-AFA was administered to ICR mice for 14 days. Compared with those in mice fed the NF, lower body weight gains and epididymal fat pad tissue weights were observed in mice fed the diet containing F-AFA. After feeding, the caecal microbiome was analysed by 16S rRNA (V4) gene amplicon sequencing using the Illumina MiSeq system. Sequences were clustered into operational taxonomic units, with a 97% identity cutoff, using the QIIME2 workflow script and SILVA database. The caecal microbiome alpha diversity was high in mice fed the F-AFA diet. The abundances of Muribaculum- and Alistipes inops-like bacteria belonging to the phylum Bacteroidetes and Ruminococcaceae UCG-014-like bacteria belonging to phylum Firmicutes were higher in the F-AFA group than in the AFA group. Isolation of typical F-AFA-susceptible gut indigenous bacteria and functional studies of the isolates in the presence of F-AFA are warranted to validate the current findings.