An in vitro pilot fermentation study on the impact of Chlorella pyrenoidosa on gut microbiome composition and metabolites in healthy and coeliac subjects

The response of a coeliac and healthy microbiota to the green algae Chlorella pyrenoidosa was evaluated using an in vitro continuous, pH controlled gut model system, which simulated the human colon (vessel 1, proximal colon; vessel 2, transverse colon; vessel 3, distal colon). The effect of C. pyrenoidosa on the microbial composition was determined by 16S rRNA gene sequencing and the impact on metabolic activity was measured using 1H-nuclear magnetic resonance (1H-NMR) spectroscopic analysis. Substantial differences in beta diversity and short-chain fatty acids (SCFAs) production were noted between the coeliac and healthy donors at the baseline. The addition of C. pyrenoidosa significantly increased the abundance of the genera Prevotella, Ruminococcus and Faecalibacterium in the healthy donor, while an increase in Faecalibacterium, Bifidobacterium and Megasphaera and a decrease in Enterobacteriaceae were observed in the Coeliac donor. Functionally, the daily addition of C. pyrenoidosa altered SCFAs production in both donors. A significant increase from baseline was seen in butyrate and propionate (P < 0.0001) in the healthy donor, especially in vessel 2 and 3. While acetate was significantly higher in the healthy donor at baseline in vessel 3 (P < 0.001) compared to the coeliac donor, this was markedly decreased after in vitro fermentation with C. pyrenoidosa. This is the first in vitro fermentation study of C. pyrenoidosa and the human microbiota and our results show that C. pyrenoidosa can modulate the gut microbiota composition and its functionality in vitro. Human studies are needed to determine and prove its efficacy if the results can be replicated in vivo.