ABSTRACT Microalgal lipids exhibit physical-chemical characteristics similar to vegetable oils, representing alternative sources of long-chain fatty acids for food supplements. However, separating intracellular lipids from microalgae biomass is still challenging due to downstream processing technology limitations that depend on the particular microalgal species and its cultivation conditions. Thus, this work evaluated a multistep process for lipid extraction from Tetradesmus obliquus biomass instead of conventional single extraction methods to improve the lipid yield. The wet biomass was freeze-dried, the cells of the dried biomass were disrupted in a ball mill, and the milled biomass was suspended in water to obtain solid contents of 5 % and 10 % w v–1. Lipids were extracted from the aqueous suspension using the ethanol polar solvent and the hexane apolar solvent with ethanol:hexane ratios of 1:1, 1:2, and 3:5 v v–1. Tests were also carried out on the deproteinized biomass to evaluate the effect of proteins on emulsion formation since deproteinization can avoid emulsion formation. Thus, lipid downstream processing could be designed without an emulsion removal stage. The biomass was deproteinized before lipid extraction with NaOH at pH 10. The highest lipid content was verified for the 1:2 ethanol:hexane ratio, in which up to 42 % of the total lipids were extracted from the biomass. With the 3:5 ratio, the organic and aqueous phases emulsified due to the presence of lipoproteins, which hindered the lipid extraction process. Under the studied conditions, no increase in lipid extraction yield was observed with increases in the solid content or biomass deproteinization. physicalchemical physical chemical oils longchain long chain supplements However conditions Thus freezedried, freezedried freeze dried, freeze-dried mill 1 v1 v–1 ethanolhexane 11, 11 1, 1:1 12, 12 2, 2 35 3 3: stage 1: ratio 4 lipoproteins v–

RESUMO As microalgas têm sido pesquisadas como fonte sustentável de compostos bioativos para as indústrias alimentícia e farmacêutica. Os objetivos deste trabalho foram extrair, caracterizar ácidos graxos de Scenedesmus obliquus e separar, quantificar e avaliar a capacidade antioxidante de carotenóides e compostos fenólicos desta microalga. As células de microalga foram rompidas usando ultra-som. Determinou-se a composição centesimal das células liofilizadas. Os ácidos graxos do óleo foram convertidos em ésteres metílicos e analisados por cromatografia gasosa (detector de ionização de chama) para obtenção do perfil de ácidos graxos. Acetona, éter de petróleo e hexano foram os solventes aplicados para extrair os carotenóides e o etanol foi utilizado para separar os compostos fenólicos. A atividade antioxidante dos extratos foi determinada pelo método DPPH. A quantidade de ácidos graxos poliinsaturados correspondeu a 47,31% do total para insaturados, com predomínio de ácido linolênico (16,74%) e aproximadamente 9,70% de ômega-6. O teor de carotenóides extraídos foi maior usando hexano. Concentração fenólica total de 1,12 g∙100 g-1 microalga foi encontrada. Altos percentuais de inibição da oxidação foram observados para os extratos de carotenóides (> 88%) e compostos fenólicos (> 72%). Portanto, Scenedesmus obliquus apresenta-se como uma fonte alternativa, natural e sustentável de compostos bioativos.

ABSTRACT Microalgae have been researched as a sustainable source of bioactive compounds for the food and pharmaceutical industries. The objectives of this work were the extraction and the characterization of fatty acids of Scenedesmus obliquus and to separate, quantify, and evaluate the antioxidant capacity of carotenoids and phenolic compounds of this microalga. The microalga cells were disrupted by using ultrasound. The centesimal composition of lyophilized cells was determined. Fatty acids of the oil were converted into methyl esters and analyzed by gas chromatography (flame ionization detector) to obtain the fatty acid profile. Acetone, petroleum ether, and hexane were the solvents applied to extract the carotenoids and ethanol was used to separate the phenolic compounds. The antioxidant activity of the extracts was determined by the DPPH method. The amount of polyunsaturated fatty acids corresponded to 47.31% of the total for unsaturated, with the predominance of linolenic acid (16.74%) and approximately 9.70% of omega-6. The content of extracted carotenoids was higher by using hexane. Total phenolics concentration of 1.12 g 100 g-1 microalga was found. High percentages of oxidation inhibition were observed for the extracts of carotenoids (>88%) and phenolic compounds (>72%). Therefore, Scenedesmus obliquus presents itself as an alternative, natural, and sustainable source of bioactive compounds.