EFEITOS DA CAFEÍNA NO CRESCIMENTO E NA COMPOSIÇÃO QUÍMICA DE MICROALGAS.

This study aimed to evaluate the removal of caffeine and its effects on growth and chemical composition of microalgae. The strains Spirulina platensis and Scenedesmus obliquus were cultivated for 40 days in medium with 20 (C20) and 40 mg.L-1 (C40) of caffeine (Stage 1). Caffeine photodegradation was evaluated for 20 days in microalgae culture media without the presence of strains. Scale-up cultivations (Stage 2) were performed with S. platensis and caffeine at the same concentrations. The chemical composition of the biomasses was evaluated at the end of the cultivations in both stages. The microalgae showed ability to grow in C20 and C40, with S. platensis being the most resistant strain. Furthermore, S. obliquus was able to remove 13.66% of the initial concentration of caffeine in C20, while S. platensis showed a greater growth in Stage 2 compared to Stage 1, which resulted in higher removal efficiency in the second stage (25.64% for C20; 13.33% for C40) than in the first stage (0.18% for C20; 12.31% for C40). There was no photodegradation observed in 20 days. Caffeine induced the accumulation of proteins in the biomasses, with values up to 57% (S. obliquus, C20). The high values of proteins demonstrate the possibility of using these biomasses to generate products such as biomethane and biofertilizers. The microalgae were able to grow in high concentrations of caffeine, showing promising for its removal and use of the generated biomasses, requiring further studies in order to improve the removal efficiencies during the microalgal bioremediation processes. [ABSTRACT FROM AUTHOR]