Different cultivation methods of microalgae for biotechnological applications

The aim of this Thesis entitled "Different cultivation methods of microalgae for biotechnological applications" is to increase knowledge on the morphophysiological and biochemical aspects of certain microalgae that are widely used in the bioenergy, pharmaceutical and nutraceutical sectors. The research focused on the two microalgae which are known for their use in biotechnology Tisochrysis lutea and Nannochloropsis oculata, in order to improve their growth performance, photosynthetic efficiency and biomass composition. The Thesis is organized and subdivided in chapters as follows: Chapter 2 is a study on the feasibility of co-cultivating T. lutea and N. oculata in a batch system in saline medium. This strategy could aim to obtain distinctive compounds of each alga, such as pigments (chlorophylls and carotenoids) and fatty acids (e.g. DHA and EPA), in a single cultivation process with the concomitant advantage to halve water and nutrient use. Chapter 3 focuses on the effects of two different illumination conditions on mono- and co-cultures of T. lutea and N. oculata. The results of control cultures under white light were compared with those of cultures treated with red-enriched light. In addition to studying the effects on cell growth, photosynthetic pigments and lipid content, biochemical analyses were also performed to highlight any adaptations of the two microalgae in the photosynthetic apparatus in response to the different light conditions. Chapter 4 aims to evaluate the feasibility of cultivating T. lutea in rejected brine from the desalination plant of Almería (Spain). A waste-to-value approach was applied to produce microalgal biomass rich in valuable molecules such as lipids and pigments from an industrial by-product, with the added advantage of increased environmental sustainability associated with reduced freshwater consumption. Chapter 5 concerns a comparative study on cell growth, lipid accumulation, photosynthetic performance and antioxidant activity of T. lutea grow under autotrophic and mixotrophic conditions using glycerol as a carbon source. Furthermore, a semi-continuous culture strategy was proposed in other to maximise the possibility of growth of this alga.