Isolation, characterization and evaluation of pollutants tolerance in microalgae

Algae can be classified into "macroalgae", i.e. multicellular photosynthetic organisms prevalently found in water, and "microalgae", i.e. microscopic unicellular photosynthetic microorganisms, ubiquitous in our planet. Microalgae are distributed both between eukaryotic microorganisms, whose cellular structure is more similar to that of the cells of terrestrial plants, and prokaryotic microorganisms, i.e. bacteria (cyanobacteria). Algae are found in almost all the terrestrial environments on our planet, both above and below the soil surface. Microalgae can be found in both marine and freshwater environments. They possess a photosynthetic mechanism, and they are able to convert sunlight energy and inorganic compounds into organic matter (energy supply) by means of the photosynthetic process, analogously to plant species. For all these reasons, they can be considered the world's largest group of primary producers in the world in terms of biomass. The use of microalgae is recognized to be an efficient and eco-friendly strategy for the removal of contaminants from wastewater. Due to their versatility, microalgae can grow in a broad spectrum of wastewaters, including those from agricultural, animal, municipal, and industrial sources, while converting nutrients, such as nitrogen and phosphorus, into useful products. Currently, despite microalgae are starting to be exploited at large scale for the treatment of agricultural and municipal wastewaters, novel applications for specific types of wastewater, such as from petrochemical sources, are still in their early stages. Thus, further work should be performed to optimize microalgal technology in light of its application to industrial contexts. Currently, there is also an increasing interest in making these technologies even more economically and environmentally sustainable by using microalgal biomass, obtained during wastewater remediation processes, to produce novel bioplastic materials, potentially replacing petroleum-based counterparts and reducing the adverse impact of human activities and manufacturing on the environment. The present thesis aimed at i) isolating and characterizing new native microalgal strains from aquatic environments in the regional territory, and ii) elucidating their possible role in the treatment of heavy metal and common pollutant contaminations by means of phycoremediation. The resistance patterns of a panel of 7 microalgal strains of both marine and freshwater origin towards five metals was evaluated; four newly isolated Chlorella sp. microalgal strains from the Lake Massaciuccoli were isolated as well and investigated for their resistance patterns towards common pollutants (antibiotics, herbicides, ibuprofen), metals and olive oil mill wastewater. Moreover, the complete characterization of the Chlorella-like native strain SEC_Li_ChL_1 was performed by means of an integrated multidisciplinary approach involving molecular, morphological and metabolical analyses. Finally, the characterization of two bacterial strains strictly associated to the phycosphere of strain SEC_Li_ChL_1 was performed, in order to evaluate their possible role in the implementation of the growth and in the pollutant tolerance ability of the microalgal strain.