Résumé
Spontaneous fermentation is a process widely used around the world for millennia. Although studies have characterized the microbiota and the impact of fermentation on the nutritional composition of several traditional cereal-based fermented foods, they have not yet studied fermented couscous, a staple food in Senegal, made from a variety of cereals.Thus, this study aims to characterise the microbial composition of such fermented couscous from Senegal and the effect of the fermentation on their nutritional qualities.Forty samples from flours of different cereals (sorghum, maize, millet, and a mix of maize and millet) were collected in Senegal before and after fermentation (flours moistened into small balls, fermented for 8 hours). We analysed microbial diversity and metabolic functionalities using shotgun metagenomic sequencing. We also measured vitamin B9 content, as fermentation can significantly alter its levels.Each flour had a specific microbial diversity, with maize flours exhibiting the lowest diversity. Lactobacillaceae, especially from the genus Weissella, were in high proportions in all flours. Millet flour contained potentially pathogenic bacteria from Enterobacteriaceae family. Surprisingly, besides the expected presence of Lactobacillaceae after fermentation, a low proportion of species from Acinetobacter genera, previously undetected in flours, appeared. We detected only species of yeasts from the Saccharomycetales order in 28% of flour samples.Despite the presence of potential folate-producing microbes, vitamin B9 content decreased during the fermentation. Analysis of functions from metagenomic data will help better understand the metabolic interactions within the traditional microbial food ecosystem and help to know more about their potential nutritional properties.