Efeitos de diferentes condições físicas e efluentes agrícolas sobre o cultivo de microalgas da família Scenedesmaceae como subsídio à aplicação biotecnológica.

• Autor(a) principal: Costa, Adriano Goldner
• Data de Publicação: 2018
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/10042
• topic: Biofuels; Bioremediation; Effluents; Light; Microalgae; Temperature; Efluentes; Luz; Microalgas; Temperatura; Agronomia; Biocombustíveis; Biorremediação; Microalga x Cultivo; 57

Microalgae cultivation presents several applications of economic and environmental interest, such as obtaining compounds for human and animal food supplementation, waste water treatment and, more recently, the biofuels production. Studies with the light and temperature manipulation, as well as the use of agricultural effluents as alternative cultivation mediums, can make possible the increase of the microalgal biomass, reducing the production costs. In this study, the effects of different temperature conditions (25ºC, 30ºC and 35ºC) and luminosity (without shading, 50% shading and 70% shading) on the Desmodesmus communis growth and biomass were evaluated. Different agricultural effluents concentrations (residual hydroponic solution of lettuce culture and biodigested swine residue) were also tested as alternative means for the Scenedesmus acuminatus cultivation, in order to evaluate its biotechnological potential, to minimize productive costs and to mitigate environmental impacts. Three treatments with different concentrations of each effluent (20%, 30% and 40% of the hydroponic residue, and 10%, 15% and 20% of the swine effluent) and a control with ASM1 synthetic medium were established. Growth analyzes, dry biomass, a and b chlorophyll, total carotenoids, water soluble protein content, total carbohydrates and lipids, fatty acid methyl esters profile, and nutrient removal percentage and electrical conductivity reduction of the mediums were performed. In the experiments with different temperatures and shading, D. communis showed great tolerance to the variations tested (25-35ºC and up to 50% shading), showing no significant differences between growth parameters, dry biomass and a chlorophyll. However, under shading 70% the microalga presented significant limitation on maximum cell yield, dry mass and chlorophyll. In the tests with the use of residual hydroponic solution and biodigested swine effluent, S. acuminatus acted as an efficient bioremediation agent, significantly reducing the nitrogen and phosphorus concentrations of these residues (68,5-99,8%). The 40% hydroponic effluent culture was characterized by a microalgal biomass rich in proteins (44,2%), a and b chlorophyll (9799 µg.L-1 and 2730 µg.L-1 , respectively), carotenoids (4826 µg.L-1 ), besides fatty acids of great nutritional value, such as linolenic acid (19,5%), suggesting its use as a human and animal food supplement. The microalgae cultivation in swine effluent after biodigestion showed low efficiency in terms of productivity and useful biomass, being unviable to algal growth in concentrations higher than 10% residue. For the two evaluated effluents, the fatty acid methyl esters total content presented low yield (20,1-64,3 mg.g-1 ), which compromises their application in the industry for the biodiesel production. On the other hand, the high carbohydrate content in crops with 20% and 30% hydroponic effluent (44,1 and 34,4%, respectively), suggest its use in the bioethanol production. Based on the results, it was concluded that D. communis showed to be tolerant to variations in light and temperature, showing potential to be cultivated on a larger scale, and S. acuminatus showed high efficiency in the bioremediation of the tested agricultural effluents. In addition, in the cultures with residual hydroponic solution, it was possible to produce a microalgal biomass with great biotechnological potential.