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Renewable source biofuels are a promising alternative to fossil fuel and can be economic and environmentally viable when associated with effluent gas and wastewater treatment. This work proposes the study of lipid accumulation and microalgae cultivation using vinasse which is a residue from sugarcane bioethanol production. Besides being a largely produced effluent that requires bioremediation, vinasse is a carbon and nutrient rich source that could be advantageous as microalgae cultivation medium. Therefore, the objective of this research is to cultivate the microalgae strain Desmodesmus sp. in different types of undiluted vinasse medium (raw, raw recycled and biodigested) in a photobioreactor system. Cultivation was performed under different conditions varying: I) bubble agitation; II) temperature; III) light incidence; IV) flux of atmospheric air supplemented with CO2. Biomass concentration was measured by cell density, lipid accumulation was measured gravimetrically after solvent extraction, and vinasse biochemical composition was determined usingTOC-VCSN Shimadzu® analyzer. The levels of dissolved O2 and CO2 were monitored using O2 and CO2 electrodes, respectively. Raw vinasse with relative biomass concentration of 1.5 g L-1 showed to be preferred medium for high lipid accumulations and carbon consumption. The maximum lipid content of 24.48% wasobtained under heterotrophic, aerobic (0.05 VVM) growth conditions, at a temperature of 26 °C, without magnetic agitation and CO2 presence. However, for effluent treatment, better results were obtained under mixotrophic, aerobic (0.05 VVM) and bubble agitated growth conditions, at 26 °C of temperature. Recorded carbon reduction was 46.35%. As vinasse consists of an organic carbon and nutrient source, cultivation cultures are susceptible to contamination by other microorganisms. Therefore, further study is necessary to the use of Desmodesmus sp. microalga for either biodiesel production or bioremediation.

Microalgal biomass have a potential to be used as feedstock for biodiesel production because of high photosynthetic rates, high biomass production, faster growth in comparison to traditional feedstocks and to not be competitive with food production. In this paper, the growth and lipid content of three microalgae strains, namely Chorella vulgaris, Desmodesmus sp. and Desmodesmus brasiliensis, were studied during 9 days of mixotrophic cultivation. The laboratory scale experiments were carried out in BG-11 media enriched with 10 g/L glucose at initial medium pH of 7.5, temperature of 26 ± 4 °C and light flux of 62 µE m-2 s-1. The highest biomass concentration of 3.82 mg/mL was found in the Desmodesmus brasiliensis, followed with 3.64 mg/mL of Desmodesmus sp. and 3.32 mg/mL of Chorella vulgaris strain. However, the Desmodesmus brasiliensis had the lowest lipid content of 6%, followed with 13.2% of Chorella vulgaris, whereas the Desmodesmus sp. strain produced the highest lipids (19.45%).