Henok Ashagrie DERIBEW

Résumé de la thèse

B Vitamins are a group of water-soluble vitamins indispensable to humans in small catalytic amounts to maintain normal metabolic and physiological functions. Humans are incapable of synthesizing B- vitamins, which leads to strict dependence on exogenous supplies from diet and the gut microbiota. Even when B-vitamins are present in many foods, their deficiency in the general population is not uncommon. In developing countries, their deficiency can create a range of health concerns mainly associated with dietary insufficiencies arising from malnutrition.

The objective of this research project is to exploit the B-vitamin production capacity of selected bacterial strains for applications in the fight against B-vitamin deficiency. The utilization of bacteria in the fight against B-vitamin deficiency will be explored from both the food and the gut aspect.

Among the B-vitamins, this research work will focus on folate and cobalamin owing to their most pronounced health related impacts in comparison with the other B-vitamins. The role of bacteria will be explored by using Injera as a food model. Injera is an Ethiopian fermented staple food made from Eragrostis tef. The choice of injera as a food model for this project is related to its consumption by  the majority of the population in Ethiopia on a regular basis. This makes injera an excellent vehicle for delivering these vitamins to a large population

In the food aspect, the contribution of injera to the intake of B-vitamins and biofortification of this food through fermentation will be studied. In order to achieve this, the effect of processing techniques on the folate (vitamin B9) and cobalamin (vitamin B12) content of injera will be determined and a quantitative PCR measurement will be carried out to look for strains in the dough with B-vitamins producing capacity. An inoculum will then be prepared from selected B-vitamin producing bacterial strains for use in the preparation of fermented food and its effectiveness in cereal fermentation will be evaluated. In order to find optimum conditions for the inoculum production, a modelling experiment will be carried out to formulate a predictive microbiological model that provides information on the biokinetics of cell growth and B-vitamin production as a factor of temperature, pH, and other fermentation conditions.

In the gut aspect, the capacity of bacteria from the gut to synthesize B-vitamins will be explored. This will be achieved by measuring the folate content of human fecal matter samples to see the link between diet, bacterial synthesis, and incomplete absorption. The folate levels in the fecal matters will be evaluated together with dietary patterns and blood folate levels. The fecal samples will also be incubated to evaluate the folate synthesizing capacity of the bacteria from the gut.