Heterotrophic growth of green microalgae Desmodesmus subspicatus in ethanol distillation wastewater (vinasse) and lipid extraction with supercritical CO2

BACKGROUND: Single-cell lipids are obtained frommicroorganisms, including some species of microalgae, which under specific growth conditions are able to accumulate lipids in their biomass. Some species of Desmodesmus, a chlorophyceae microalgae, are considered potential sources of lipids and different cultivation systems, including heterotrophic growth inwastewater, have been proposed. This study evaluated the effect of temperature on heterotrophic growth and lipid productivity of Desmodesmus subspicatus in sugarcane processing wastewater and lipid extraction by supercritical carbon dioxide (SC-CO2). RESULTS: Results indicated lipid production by Desmodesmus subspicatus in the temperature range 15 and 40 degrees C, with the highest lipid productivity (similar to 1100 mg L-1 day(-1)) at 20 degrees C. Lipid extraction yield with SC-CO2 increased from 23 to 45% by increasing pressure from 20 to 30 MPa at 60 degrees C A cell disruption pretreatment (sonication) increased the lipid extraction yield by approximately 17%. Fatty acids profiles of the extracted lipids indicated major fractions of palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1), linoleic acid (18:2), arachidic acid (20:0) and arachidonic acid (20:4). These characteristics are interesting from the viewpoint of biodiesel production. CONCLUSION: Results suggest the feasibility of the heterotrophic production of Desmodesmus subspicatus biomass intended for lipid accumulation using vinasse, followed by SC-CO2 lipid extraction. (C) 2016 Society of Chemical Industry