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Universidade do Algarve (2019)

Phycobiliproteins accumulation in a cyanobacterium isolated from an extreme environment

Castelo, Antonio Vargas

Titre : Phycobiliproteins accumulation in a cyanobacterium isolated from an extreme environment

Auteur : Castelo, Antonio Vargas

Université de soutenance : Universidade do Algarve

Grade : Mestrado em Biologia Marinha 2019

Résumé
Cyanobacteria are photosynthetic microorganisms that can be found in different environments. This type of microorganisms has been gaining attention because of its bio-technological potential. Cyanobacteria have been shown to produce secondary metabolites including vitamins, toxins and pharmaceutical compounds. Some of them have displayed antiviral, antibacterial, antifungal and anticancer activity. Moreover, cyanobacteria have also been used as source of alternative energy or as fertilizers. All this, confirm the commercial interest of such microorganisms. Chroococcidiopsis sp. is a cyanobacterium originally isolated from Atacama Desert in Chile (phylogeny under study). Atacama Desert is characterized by extreme environmental conditions and it is considered the most arid desert in the world ; with similar conditions to Mars. Under such environment, and in order to protect from the high UV radiation and the desiccation, Chroococcidiopsis sp. has developed adaptive strategies to survive under these harsh conditions. In this sense, Chroococcidiopsis sp. was found to live inside calcite rocks, therefore being characterized as an endolithic cyanobacterium. Microorganisms found under extreme environments with high desiccation and high UV radiation are known to produce substances such as scytonemin, mycosporine, exopolysaccharides (EPS), phycobiliproteins and carotenoids to protect from the damage caused by this environment. Accordingly, and in order to evaluate the biotechnological potential of this novel strain as a phycobiliproteins producer, its growth and phycobiliproteins content will be analyzed under certain growth conditions such as light, nutrients and salt effect, under laboratory conditions, with special emphasis in phycobiliproteins, which have been already proven to have commercial applications. According to the main results, the accumulation of phycobiliproteins in batch culture under light effect was much higher when was used a light intensity of 50 μmol photons·m-2·s-1, reaching approximately values of 45 mg·g-1 for phycocyanin, 120 mg·g-1 for allophycocyanin and 80 mg·g-1 for phycoerythrin. To corroborate this result, it was analyzed in a semi-continuous experiment, which showed the same result but lower results were obtained. Moreover, the use of fertilizer showed better result when it was added to the medium of culture, in which 80 mg·g-1 of phycobiliproteins were obtained during the experiment. To obtain a better knowledge of this strain, this strain was submitted under different concentrations of salt. In spite of it, this species was only able to grow under 0.2 M of NaCl. However, the higher phycobiliproteins accumulation was produced when it was cultured under 0.4 M of NaCl, in which 14 mg·g-1 of phycocyanin, 25 mg·g-1 of phycoerythrin and 35 mg·g-1 of allophycocyanin was produced at the end of the experimente.

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