CO 2 from alcoholic fermentation for continuous cultivation of Arthrospira ( Spirulina ) platensis in tubular photobioreactor using urea as nitrogen source

Carbon dioxide released from alcoholic fermentation accounts for 33% of the whole CO 2 involved in the use of ethanol as fuel derived from glucose. As Arthrospira platensis can uptake this greenhouse gas, this study evaluates the use of the CO 2 released from alcoholic fermentation for the production of Arthrospira platensis. For this purpose, this cyanobacterium was cultivated in continuous process using urea as nitrogen source, either using CO 2 from alcoholic fermentation, without any treatment, or using pure CO 2 from cylinder. The experiments were carried out at 120 μmol photons m −2 s −1 in tubular photobioreactor at different dilution rates (0.2 ≤ D ≤ 0.8 d −1 ). Using CO 2 from alcoholic fermentation, maximum steady‐state cell concentration (2661 ± 71 mg L −1 ) was achieved at D = 0.2 d −1 , whereas higher dilution rate (0.6 d −1 ) was needed to maximize cell productivity (839 mg L −1 d −1 ). This value was 10% lower than the one obtained with pure CO 2 , and there was no significant difference in the biomass protein content. With D = 0.8 d −1 , it was possible to obtain 56% ± 1.5% and 50% ± 1.2% of protein in the dry biomass, using pure CO 2 and CO 2 from alcoholic fermentation, respectively. These results demonstrate that the use of such cost free CO 2 from alcoholic fermentation as carbon source, associated with low cost nitrogen source, may be a promising way to reduce costs of continuous cultivation of photosynthetic microorganisms, contributing at the same time to mitigate the greenhouse effect. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011