Avaliação da produção de biomassa de microalgas em meios alternativos e sua utilização como bioestimulante vegetal

Abstract

The cultivation of microalgae in the world has gained prominence due to its potential as a versatile and susteinable source of biomass, in addiction to its applications in various sectors, such as food, energy, health and environment. The search for low-cost cultivation of theses micro-organisms is the subject of several scientific studies. The use od reuse water in order to reduce the cost of production is a viable option. In this study, costs related to species nutrition were reduced by 90% when use reuse water supplemented with NPK for microalgae cultivation. In this thesis, four micralgae were cultivated in reuse water whith NPK: Chlorella vulgaris, Scenedesmus ecornis, Spirulina platensis and Spirulina labyrinthiformis. The biomass concentration of Chlorella vulgaris is increased from 0,28 g/L (in WC) to 0,55g/L (in reuse water). The biomass concentration of Spirulina platensis also increased from 0,52g/L (in Zarrouk) to 0,92 g/L (in reuse water). Scenedesmus ecornis showed a reduction in biomass concentration. Spirulina labyrinthiformis maintainded an equal concentration in the two media used. For a greater yield of the compounds, serials in the biomass were made to order. Phycocyanin, in the case of Spirulina platensis and Spirulina labyrinthiformis, reached a concentration of 98,5% and 101,06%, respectevely. There was no increase in the production of neutral lipds in any of the microalgae. The concentration of carotenoids varies according to the species. Ecotoxicological tests were carried out to determine whether the cultivation in reuse water could cause changes in the cells or if it allowed residues in the biomass to the point of causing toxicity when released into the environment. Spirulina labyrinthiformis showed toxic behavior in lettuce seeds. For further tests, Spirulina platensis was chosen to be used in all experiments of these thesis. At the end of the compound extraction stage, experiments were carried out in a incubator whith residual biomass of Spirulina platensis to evaluate the biostimulant potential in tomato seeds. Stimulating behavior was presented in the biomass when used in the germination of tomato seeds.