Valorisation of macroalgal biomasses in eco-sustainable biotechnology

Macroalgae are a grouping of multicellular photosynthesizing organisms, which live in aquatic environments, both marine and inland, and use carbon dioxide, nitrogen and phosphorus for their growth. All these characteristics make algae as an eco-sustainable resource for human beings to exploit. Macroalgae have always been used by humans as a food source, to extract phycocolloids or for other industrial activities, both collecting natural populations and farming. In many parts of the world these organisms grow in an inconsiderate way, creating inconvenience not only to the anthropic activities related to the sea, such as tourism and fishing, but also creating massive phenomena of eutrophication causing serious ecosystem damages. Moreover, some macroalgae are alien and invasive species, supplanting the autochthonous ones, often depriving the local biodiversity. In addition, macroalgal cultivation activities, when managed without the proper expertise and knowledge, can be the cause of ecological damage due to the introduction of alien species and pathogens. In processing protocols of macroalgae and their derivates, it is often necessary the use of solvents and chemicals hazardous to the environment, and research trends look towards the refining of such processes. The aim of the present thesis was to focus on the use in various fields of research, from agriculture to pharmaceuticals, of macroalgae that create large biomass, with particular attention to some Italian transitional environments. Encouraging results were obtained in the extraction of phycocolloids using microwaves, which do not affect the yield and quality of products. Polysaccharide extracts were tested for their antibiofilm, antisurfactant and antifouling activities, acting as inhibitors of microbial growth of pathogens both for human and in aquaculture. Processes for obtaining hydrocarbon were also developed and residual bioactive solutions were tested for the growth of plants of agronomic interest. The growing interest in macroalgae will lead to a greater use of both cultivated algae and biomass collected from dystrophic environments, ensuring a low ecological impact. This can be achieved through a conscious use of biomass, the knowledge of the species and their bioactive molecules, the development of eco-sustainable processes in a biorefinery perspective.