Production of bioproducts for food application from microalgae of the genus Dunaliella (Chlorophyta).

Abstract

Using microalgae to yield bioproducts that could be used for food addresses one of the most significant problems associated with population increase: unsustainable food production. In this sense, species of the genus Dunaliella, which are halophilic flagellated unicellular microalgae belonging to the phylum Chlorophyta, can produce high-quality and large amounts of bioproducts with industrial relevance, such as protein, glycerol, and pigments. However, the high-cost cultivation medium precludes large-scale of Dunaliella species for biomass production, limiting biomass production to a laboratory scale. Productivity improvement can mitigate the costs and environmental impacts associated with cultivation medium. Although there are studies on optimal conditions to increase productivity, some gaps remain, such as economic and environmental impacts associated with Dunaliella spp. cultivation, which jeopardize customers’ acceptability. In this context, this research aims to (1) analyze and identify the potential of Dunaliella spp. to produce bioproducts with industrial relevance and the conditions and pathways for their accumulation, (2) assess the market for these bioproducts; (3) improve biomass and bioproduct productivity by using different cultivation medium composition; (4) identify the bottleneck in artificial cultivation medium and how to overcome the economic aspects; (5) analyze and predict different scenarios for bioproduct production and the environmental impacts associated with the artificial medium. This thesis comprises six articles (two review articles, three experimental articles, and a life cycle assessment) to address the target objectives. The conducted studies demonstrated that (1) the global marketing for Dunaliella spp. biomass is promising, especially for food applications; (2) Dunaliella spp. can produce high-quality protein, pigments, and glycerol depending on the species, salinity, and nutrient bioavailability (mainly nitrogen), which directly impact on Dunaliella spp. composition; (3) increasing salt concentration benefits glycerol yield, while nitrogen limitation was crucial to accumulate beta-carotene; (4) sodium chloride and magnesium sulfate are two of artificial medium’s components more expensive and impactful (especially to human health and climate changes); (5) replacing sodium chloride with sea salt reduced the costs; (6) increasing biomass, glycerol, and beta carotene productivity minimized the costs and environmental damage associated with artificial cultivation medium; and (7) Dunaliella spp. cultivation to yield bioproducts can be a vector to reduce carbon dioxide emissions, reducing carbon footprint and collaborating to the green economy. It is possible to conclude with the research conducted that the most promising scenario, economically and environmentally wise, to yield bioproducts depends mainly on the productivity and species: Dunaliella tertiolecta presents better adaptation capacity and biomass and glycerol yield at higher salt concentrations, whereas Dunaliella salina shows great potential to produce high-quality beta-carotene under nitrogen-limited conditions, despite of being more restrict concerning the medium composition.