Anemia affects one third of the world's population, mostly caused by insuffisant iron intakes. Anemia and similar mineral deficiency diseases are primarily widespread in developing countries like India, partly resulting from the local diet that is mainly made up of cereal grains and seeds such as rice . In these types of food, iron bioavailability is substantially reduced by the presence of phytic acid (C₆H₁₈O₂₄P₆), which chelates minerals and forms insoluble salts which precludes their absorption in the gastrointestinal tract.

Current research on increasing the bioavailability of iron or zinc involves the bioengineering of crop plants which not only poses challenges in terms of the production of efficient genetically modified crops but also requires extensive research for drawing any conclusions on strain sustainability.

We propose an alternative strategy that focuses on the bioengineering of microorganisms involved in the fermentation of idli, a dish widely used as primary food source throughout much of India. Indeed, the lab model organism Saccharomyces cerevisiae is a strain present in the idli microbiome that naturally produces phytases. Phytases are enzymes that are able to hydrolyze phytic acid even when complexed with minerals, resulting in a greater mineral bioavailability.

However the production of phytases in Saccharomyces cerevisiae is down-regulated by two genes: PHO80, present on chromosome 15 and PHO85, found on chromosome 16. The knockout of these genes would likely increase the yield of phytase production and therefore increase the general bioavailability of minerals in fermentation-based dishes such as idli.

We used the SK1 strain of Saccharomyces cerevisiae, a gift of the INSERM unit U1001.

We transformed the yeasts with a PCR product of the G418R gene coming from the pSB1C3 plasmid surrounded by 2 short homology regions for the precise genes we wanted to excise from the yeast genome. The goal was to use the natural homology replacement mechanism of yeast to introduce a resistance inside the genes PHO80 and PHO85 to knock them out. After transformation and selection with geneticin (figure 4 is assessing that the insertions were successful) we wanted to assess the ability of the yeast to degrade phytic acid under various conditions. To do that, we used a kit to titrate, using colorimetry and OD655, phytic acid we can find in different conditions of growth of ours strains. The kit was allowing us to work directly on food samples and this is what we did, working on mixtures of rice and idli at different times of it's preparation.

In Table 1, we can see the typical data that we obtain after usage of the kit. The values are very low in comparison with what we normally have to observe (for rice is egal to 6 mg.g^-1, and here we observe a concentration of 5 µg.g^-1, 10^-3 less).

At the figure 3, we can see the histogram of the optic density post treatment with the phytic acid kit. Bigger is the free phosphorus agents and higher is the concentration of phytate in the media. As we observe, the difference between rice alone and with micro-organisms is not very high. Moreover there are no real difference between wild type S. cerevisiae and our modified strain.

We studied the differences of growth between the wild type S. cerevisiae and our three strains without pho80, pho85 or both, on YPD. The growth is not a lot affected by the suppression of this two genes, like the figure 4 shows us.