Bioprospection studies of marine microalgae for biotechnological applications.
Supervisors: José J Fdez Castro, Nathália Carneiro (U La Laguna)
Dinoflagellates are single-celled eukaryotic microalgae that have arisen attention as a rich and vast source of bioactive metabolites with great biological and chemical importance. These natural products are a result of ecological interactions, in which these substances have evolved as a mechanism of adaptation to the environmental conditions the organisms are placed in. Thus, it converts them into attractive targets for bioprospecting as a potential resource for biopharmaceutical applications. Aiming to investigate the biotechnological potential of dinoflagellates and discover new bioactive molecules, a collection of extracts was prepared for a screening for biological activities and evaluation of the chemical profile variability, through a fermentation study with two different culture media. Eight strains, distributed in four genera, were cultivated at laboratory scale. The biotechnological potential of the extracts was investigated through a screening for antiparasitic activity against three kinetoplastid parasites and two amoeba strains, antiproliferative activity against six cancer cell lines, and antimicrobial activity against pathogenic bacteria and fungi. The chemical profile of all extracts was performed on the HPLC-UV/DAD, showing qualitative and quantitative differences that reflect the biological activities results. Aiming to reduce the chemical complexity observed in the chromatograms, principal component analysis (PCA) was used to find linear combinations of the main variables that explained most of the data variability. Through the results of both biological and chemometric experiments, Amphidinium carterae, grown in Guillard-K medium, was seen as the most promising extract, being selected to a study on optimization of culture conditions. Two kinds of extracts were prepared for both biomass and culture medium. The 35-days culture cell extract showed preeminent bioactive results and was then selected to a large-scale culture for a bio-guided fractionation designed for obtaining bioactive enriched fractions and compounds, posteriorly analysed by NMR spectroscopy. After a given degree of purification, the fractions lost their bioactive potential. Even so, two compounds were isolated and are still in process of chemical elucidation analyses. Apparently, the synergism among its compounds is largely responsible for the antiamoebic and antiproliferative activities of A. carterae extracts. However, as a great advantage, synergetic effects have been rising attention for pharmaceutical applications. Few substances have been isolated from dinoflagellates, especially because of its complex chemical structures. Therefore, this study shows the high capability to obtain natural products from microalgae with ample pharmacological applications, in which more investigations must be developed to better understand these bioactive responses, particularly with a synergetic action. This work is grounded on the blue technology field that is concerned with the valorisation and exploitation of marine organisms to create new assets for sustainable growth based on the bioeconomy. In this manner, the implementation of dinoflagellates’ cultivation ensures a substantial action for generating a sustainable supply of bioactive molecules. This study brings faithful reasons that microalgae have unique ecological characteristics, being a promising inexhaustible source of natural products that can be bioprospecting exploited without harming the marine environment.