Carbon dioxide from alcoholic fermentation as a carbon source for fed-batch cultivation of Arthrospira platensis

World’s production of ethanol has increased dramatically in recent years. Brazil is the world’s largest exporter of bioethanol and second-largest producer after the United States. Considering the increasing demand for this fuel and the fact that alcoholic fermentation is responsible for a CO2 release, on weight basis, almost coincident with ethanol production, it would be interesting to develop a process for CO2 fixation able to turn it into a useful product. Photosynthetic microorganisms can fix CO2 efficiently producing biomass that contains high-value bioactive products and may provide a very promising alternative for the current CO2 mitigation strategies. Nowadays, there are numerous commercial applications of Arthrospira platensis biomass such as the enhancement of the nutritional value of foods and animal feed, bioremediation, and use in cosmetics. The objective of this work was to evaluate the Arthrospira platensis cultivation using CO2 from alcoholic fermentation and either urea or nitrate as nitrogen source at different light intensities (60 ≤ I ≤ 240 μmol photons m-2 s-1). The CO2 source (pure CO2 or from alcoholic fermentation) did not influence the maximum cell concentration (Xm), cell productivity (PX) and nitrogen-to-cell conversion factor (YX/N). On the other hand, the use of urea instead of nitrate led to higher YX/N values. Xm and PX increased when I was increased from 60 to 120-240 μmol photons m-2 s-1. Using CO2 from alcoholic fermentation, the best performance (Xm = 2952 ± 35 mg L-1, PX = 425 ± 5.9 mg L-1 d-1 and YX/N = 15 ± 0.20 mg mg-1) was obtained at I = 120 μmol photons m-2 s-1 with urea. The results obtained in this work demonstrate that urea and CO2 from alcoholic fermentation could be simultaneously used in large-scale cultivations to reduce the environmental impact associated to the release of this greenhouse gas as well as to decrease the production cost of this cyanobacterium.