RESUMOUm dos materiais alternativos mais investigados atualmente para a produção de biodiesel são as microalgas. O presente trabalho teve como objetivo a avaliação do método de transesterificação enzimática in situ da microalga Desmodesmus sp. em solvente orgânico, acompanhando a reação através do monitoramento on-line com sonda de infravermelho e cromatografia gasosa. Dois ensaios foram realizados em condições distintas para efeito comparativo. Baseado nos resultados obtidos por espectroscopia e cromatografia, bem como nas propriedades calculadas a partir do perfil cromatográfico, pode-se concluir que é possível à produção de biodiesel in situ a partir de biomassa de microalgas, reduzindo a etapa de extração de óleo. Palavras-chave:Microalga. Desmodesmus sp. Biodiesel. Transesterificação in situ. Espectroscopia de infravermelho. Cromatografia gasosa. ABSTRACTOne of the most investigated alternative materials for the production of biodiesel is microalgae. The present work had the objective of evaluating the in situ enzymatic transesterification method using the microalga Desmodesmus sp. in organic solvent, following the reaction through online monitoring with infrared spectroscopy and gas chromatography. Two experiments were carried out under different conditions for comparative effect. Based on the results obtained by spectroscopy and chromatography, as well as the properties calculated from the chromatographic profile, it can be concluded that it is possible to produce in situ biodiesel from microalgae biomass, eliminating the oil extraction step.

Introduction: Mixotrophic microalgae systems have great potential for bioenergy production and wastewater treatment. Anaerobic-treated wastewater supplemented with carbon can improve biomass yield and quality, as it presents low carbon content. Alternative carbon sources in microalgae cultivation, such as glycerol, are essential for minimizing the economic and environmental impacts caused by biomass production, and improving the profile of fatty acids. This study aimed to increase biomass production and the lipid content with glycerol as the carbon source for microalgae cultivation from sanitary wastewater. Materials and Methods: The microalgae behavior in the wastewater was pilot tested using glycerol supplementation at 7.5, 10.5, and 12.5 g L-1. Results: In all the experiments with sanitary wastewater, the microalgae production presented Chlorella sp. as the predominant species. The best biomass (3.78 ± 1.12 g L-1) and lipid (35.67 ± 0.80%) yields were found at 12.5 and 10.5 g L-1 of glycerol, respectively. Conclusion: The microalgae produced more lipids with glycerol supplementation. An attractive profile for biodiesel was found regarding the fatty acids in the biomass.