Utilização de microalgas na biotecnologia, com ênfase para biodiesel e análise de imunoparâmetros em camarões marinhos

Abstract

Microalgae are unicellular organisms capable of using solar energy and carbon dioxide with high photosynthesis efficiency to produce biomass, and are easy to cultivate. Due to these characteristics, they have been the object of research, especially in the fields of aquaculture and biotechnology. This thesis, consisting of four chapters, had as its first objective to evaluate the efficiency of different extraction methods of biomass oil from cultures of microalga Chlorella vulgaris. Four of these methods were ultrasound-assisted (cold) and one by heating. After determining the best method for lipid extraction, we evaluated the influence of salinity of the culture medium in biomass recovery and oil yield for ten microalgae cultivated in Guillard f/2 medium. Next, the influence of different amounts of sodium nitrate was evaluated in the culture medium for biomass recovery and oil yield for four microalgae. Lastly, biomass recovery and oil yield was determined for C. vulgaris cultivated outdoors, and the main fatty acids present in the oil for biodiesel production were identified. Also, the performance and certain immunoparameters of marine shrimp Litopenaeus vannamei were evaluated following inclusion of biomass obtained from outdoor microalgae culture in the diet, before and after the oil extraction process. Lipid extraction using the Bligh and Dyer method showed the highest yield (52.49±3.37%) among the ultrasound-assisted methods. Of the ten microalgae cultivated under different salinities, six saw their oil yields increase when salinity was reduced from 35 to 25; the highest increase (eight-fold) was observed in Tetraselmis sp., whereas oil yield increased in three species when salinity was raised from 25 to 35, with a threefold increase for C. vulgaris. The higher amounts of sodium nitrate in cultivation media resulted in increased biomass recovery from microalgae Nannochloropsis oculata and C. vulgaris, whereas the reduction in the quantity of this nutrient resulted in higher oil yields for all microalgae, especially for the species described above. Finally, it was observed that certain growth performance parameters of marine shrimp were vastly superior in the experiment using inclusion of natural C. vulgaris biomass in replacement of defatted biomass, although 0.5% inclusion of the latter also showed satisfactory results. With regard to immunoparameters, inclusion of natural or defatted biomass of C. vulgaris in the diet of shrimps, regardless of amount used, increased the concentration of total proteins and reduced phenoloxidase activity in animal serum.