Résumé
Like in many developing countries, the traditional Ethiopian diet relies mainly on starchy staple foods and often lacks sufficient animal-sourced foods which are crucial for cobalamin intake. Furthermore, the concentration of folate in traditionally prepared injera, an Ethiopian cereal-based fermented staple food, is highly variable and injera contains biologically inactive corrinoids. This study aimed to improve the cobalamin and folate content of injera by using cobalamin-producing Propionibacterium freudenreichii and folate-producing Lactiplantibacillus plantarum strains, both individually and combined. Since injera is fermented using backslopping, we also assessed the ability of these strains to produce cobalamin and folate consistently across successive fermentation batches. Changes in the microbial ecosystem were monitored using real-time PCR. The theoretical contribution of the injera prepared using the selected strains to the cobalamin and folate intake of children and women of reproductive age was also calculated. Results showed that using the selected bacterial strains individually increased cobalamin (up to 19.2 μg/100 g of dry matter) and folate (up to 180.2 μg/100 g of dry matter) levels in the injera dough over several backslopping fermentation batches. Regular consumption of the injera with enhanced vitamin content produced using each strain alone would be capable of fulfilling the entire recommended nutrient intake for cobalamin and up to 29 % of the recommended intake for folate for children and women of reproductive age. However, when the strains were used together, the production of both vitamins was reduced. The presence of certain common endogenous bacterial species and genera exhibited significant variability, highlighting the complex response of the native microbiota to the different inoculation strategies employed. Future experiments should consider selecting a microbial consortium comprising non-competing microorganisms to ensure the simultaneous production of cobalamin and folate in fermented foods.