Estudio de elementos esenciales y tóxicos en microalgasuso de Chlorella sorokiniana en la preparación de alimentos funcionales

Résumé

Microalgae have a great interest because their combine photosynthetic activity with nutritional requirements and biotechnological potentiality, which together to a simple cellular structure and high growth rate allow multiply several times the number of cells in a short period of time, accumulating valuable metabolites. They are easy manipulated microorganisms in the laboratoiy and can be used as vegetal models for metabolic pathways research. This combination of vegetal cell with fast growing microorganism has promoted their use the choice of them for the different aims of this PhD Thesis. In recent years, there is a special interest in foods that are not only nutritious but also provide a beneficial health effect. In this way has emerged functional food production based on recent technologic approximations with high added value, well characterized with defined toxicological, nutritional and metabolic profiles. Recently, it has been highlighted the potential of algae as functional substances source and particularly selenium compounds, element with high therapeutic properties in cancer prevention, cardiovascular diseases, immune systems, and neurological impairments. New analytical technologies, particularly speciation approaches based on HPLC-ICP-MS couplings and fast extraction techniques for chemical species together to confirmatory approaches for chemical substances based on HPLC-MS-MS or tandem mass spectroscopic techniques (QqQ y QqTOF), are open new alternatives for unknown compounds characterization. In addition, the development of metallomic techniques based on multidimensional chromatographic (SEC/HPLC) and ICP-MS detection allows the identification of metallobiomolecules combined with ESI-Qq-TOF-MS, which are very powerful and innovative tools for biotechnological developments. Present study considers the possible use of microalgae Chlorella sorokiniana for human and animal consumption, considering the possible bioaccumulation of iodine and selenium and the chemical forms of these element produced by the algae, as well as the associated metabolism to control the production of bioactive species and formation of undesirable toxic substances as well as the global process yielding to get optimum conditions of production. Parallel to analytical study was optimized the biotechnological process at laboratory scale, to establish tolerance limits of these essential elements for the algae, the distribution profile of the element among cell macromolecules, together to improvement of biotechnological strategies for element accumulation enhancement. Due to the easy incorporation of selenium by the microalgae and high content of selenomethionine this algae is a promising candidate to produce a functional food enriched in this element. In order to results to establish selenium bioavailability, an in vitro approach was used to access microalgae selenium bioaccessibility using algae enriched in this element by simulation of gastrointestinal digestion. Further, in vivo exposure experiences to enriched microalgae were performed on mice Mus musculus. For this purpose it has been applied a metallomic approach to cytosolic extracts from organs and serum of Mus musculus, in order to identify expression changes of metallobiomelecules associated to a diet rich in selenium. On the other hand, because it is a unicellular organism, Chlorella has a simple metabolism that allows simple exposure assays to toxic elements, which can be extrapolated to more complex organisms. This fact converts the microalgae in a veiy suitable bioindicator in toxicity studies, environmental pollution, and antagonist effects and interactions between contaminants and protective substances. The final conclusion is that selenium can protect against mercury toxicity on the basis algae exposure experiments to methylmercury and selenomethionine, with special attention in the effect of selenomethionine chirality on the reduction of organic mercury toxicity.