Microalgasfuente de compuestos de interés comercial

Abstract

Microalgae have generated a special interest in recent years because of the extraordinary potential they present. Their fast and easy growth and the ability they have to convert solar energy into biomass have led to the development of different cultivation techniques in order to obtain numerous and varied products of commercial interest. During photosynthesis, using only light and nutrients, microalgae can produce high added-value metabolites such as lipids, proteins, carotenoids, carbohydrates and hydrocarbons. The generated amounts of these metabolic products are closely related to environmental conditions, in particular, to the amount and intensity of light, temperature, pH, salinity and nutrient availability. Therefore, al! these factors have a great influence on the biochemical composition of microalgae and, eventually, on biomass production. These high value products present a wide range of applications in food, cosmetics, pharmaceutical industry, as well as in the manufacture of biopolymers. Among these compounds are those studied in this Doctoral Thesis, which were carotenoids, carbohydrates (exopolysaccharides) and hydrocarbons. From a commercial point of view, carotenoids are the most interesting photosynthetic pigments far their use as feed additives, especially as color enhancers. Of all known carotenoids, -carotene, lutein, zeaxanthin and astaxanthin are most commonly used for commercial purposes. On the other hand, the production of hydrocarbons and polysaccharides from microalgae and other plants is becoming a field of interest related to the generation of chemicals and polymers derived from renewable resources. The primary components of the major commercial polymers are derived from sugars (polyesters) and hydrocarbons (polyolefins), which are produced by certain algae. The interest in these compounds lies on their broad spectrum of application in the industry, in the current strong dependence on the availability of fossil resources, as well as on the sustainability of the production of bio-derived chemicals and polymers. This Doctoral Thesis is focused on the ability of certain microalgae to accumulate compounds with high added value, such as the aforementioned carotenoids, carbohydrates and hydrocarbons. Several microalgae isolated from Ria Tinto (Huelva) were studied, from which the one with the best productivity was selected for further experiments and identified as Coccomyxa onubensis. And other two races (A and B) of a microalga from a totally different environment environments with high temperatures, irradiance, dissolved metals, acid pH and lack of essential nutrients, which increases its metabolic response to the biosynthesis of antioxidant molecules, including carotenoids (P-carotene, zeaxanthin, astaxanthin and lutein), B. braunii is characterized by its slow growth and, at the same time, by being able to synthesize and accumulate large amounts of compounds as interesting as exo-polysaccharides and hydrocarbons. Thus, in the case of C. onubensis, the effect of difierent factors, such as temperatura and ultraviolet radiation A and 8, on the growth and production of carotenoids was studied. In the case of B. braunii, the optimization of the culture medium was carried out as a first approach, and commercial fertilizers were subsequently used to reduce costs and to see if it was possible to increase growth and carbohydrates and hydrocarbons productivity. The results obtained in this Thesis have contributed to obtain higher productivities of biomass and metabolites far both microalgal species.