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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]

The recent detection of emerging contaminants in soils, waters and effluents, which can have adverse effects on organisms and the environment, has triggered numerous studies aimed at the removal and degradation of these contaminants. Microalgae are an alternative treatment for removing contaminants and, with the remaining biomass, by-products can be produced. The objective of the present work was to evaluate the cellular composition of microalgae after cultivation in synthetic media containing different mixtures of drugs. Chlorella homosphaera and Scenedesmus obliquus were grown in 250 ml erlenmeyer flasks, placed on a shaking table with temperature control and photoperiod, for 20 days. Five experiments were performed with the drugs caffeine, acetylsalicylic acid (ASA), diazepam, paracetamol and fluoxetine, along with 2 control experiments. At the end of the 20 days, the culture was centrifuged to separate the biomass and prepare the extract for quantification of carbohydrates and proteins by spectrophotometric methods. Chlorella showed higher quantification of carbohydrates in the experiment containing diazepam, caffeine and ASA (37%), in contrast to the experiment containing fluoxetine, caffeine and ASA (20.58%) and the experiment with the 5 drugs (20.69%). Scenedesmus, on the other hand, had expressive values of protein, the highest quantification being found in the experiment containing fluoxetine (82.72%) and the lowest value in the assay with the 5 drugs (54.85%). Cultivation in the presence of drugs altered the biochemical composition of microalgae, making it possible to manufacture products such as biofuels, for example. For use in other matrices, it is necessary to investigate the biomass toxicity. [ABSTRACT FROM AUTHOR]