Abstract
Folate (vitamin B9) and cobalamin (vitamin B12) deficiencies have significant health implications, particularly in low- and lower-middle-income countries where diets rely on starchy staple foods that offer folate but lack cobalamin. Inadequate intake of animal-sourced foods, the primary cobalamin sources, is also a concern in developed countries due to shifting dietary patterns towards plant-based diets. Certain bacteria can synthesize these vitamins in food fermentation and the human gut, yet their roles in cereal-based fermented foods and their folate-producing potential in the gut remain underexplored. Therefore, this thesis aimed to explore the potential contributions of bacteria in addressing folate and cobalamin deficiencies. First, the folate and cobalamin content of injera, a traditional Ethiopian cereal-based fermented staple food prepared from teff through backslopping fermentation, was explored, and shown that injera can provide 5% to 23% of the recommended folate intake for women of reproductive age. However, cobalamin found in injera was biologically inactive in humans. Fermentation was dominated by lactic acid bacteria and, with specific species correlating with folate and cobalamin levels. Second, the feasibility of increasing folate and cobalamin content in injera was explored using folate- and cobalamin-producing bacterial strains. Applying these strains individually significantly increased folate and cobalamin levels in injera dough over multiple backslopping rounds, meeting recommended cobalamin intake and providing up to 29% of folate for women of reproductive age. However, when used together, the strains were less efficient. The evolution of microorganisms, including those present before inoculation, potentially influenced vitamin production. Finally, the influence of diet and gut microbiota on the folate status of reproductive-age women (n=10) was assessed. Participants consumed the folate-enriched injera and a rice-based low-folate diet for 3 days in a crossover design. Regular consumption of folate-enriched injera covered 70.1% of the recommended folate intake. During the period of the low-folate diet, folate concentrations in excess of dietary intake were observed, indicating a significant contribution of microbially synthesized folate. In vitro measurements of folate concentration in fecal matter illustrated varying folate production and consumption capabilities of the gut microbiota among individuals and across different dietary folate intake periods. This study highlighted the complex relationship between microorganisms and their potential roles in improving the folate and cobalamin status of individuals.