Microalgal biorefinery: effect of sugarcane vinasse cooling on the heterotrophic growth and biodiesel production by Phormidium autumnale

Abstract

Abstract The use of microalgae in the wastewater treatment has been studied due to efficiency of nutrients removal and waste valuation for obtaining a biomass with economic interest. Filamentous Phormidium autumnale is recognized as a robust species normally found in extreme environments due to its tolerance to limiting conditions. Vinasse is the main wastewater in the sugarcane processing with a high polluting impact, originally obtained at high temperatures from output of alcoholic distillation, and requires the cooling for biological treatment. Microalgal biodiesel with adequate properties could be made possible from the use of agro-industrial by-products, according a “biorefinery” concept. It is important to evaluate the effect of this gradual cooling of the culture medium on the kinetic parameters of growth and removal of carbon and nitrogen from vinasse, as well as, fatty acid profile in microalgal biomass with estimate the properties of a potential biodiesel. Results indicated maximum specific growth rates around 0.05 h− 1 and maximum carbon and nitrogen removals of 30 and 38%, respectively, after 72 hours. Fatty acid profile indicated palmitic acid (C16:0) with the highest occurrence (28% mass/mass), followed by linoleic acid (C18:2), stearic acid (18:0) and eicosapentaenoic acid (C20:5). Results indicate that the cyanobacterium Phormidium autumnale is tolerant to temperature variations and presents potential use in this vinasse wastewater for biomass and biodiesel production.