CO2 from Alcoholic Fermentation for Continuous Cultivation of Arthrospira (Spirulina) platensis in Tubular Photobioreactor Using Urea as Nitrogen Source

摘要

Carbon dioxide released from alcoholic fermentation accounts for 33% of the whole CO2 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 CO2 released from alcoholic fermentation for the production of Arthrospira platensis. For this purpose, this cyanobacte-rium was cultivated in continuous process using urea as nitrogen source, either using CO2 from alcoholic fermentation, without any treatment, or using pure CO2 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 CO2 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 CO2, 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 CO2 and CO2 from alcoholic fermentation, respectively. These results demonstrate that the use of such cost free CO2 from alcoholic fermentation as carbon source, associated with low cost nitrogen source, may be a promising way to reduce costs of continuous cultivation of photo-synthetic microorganisms, contributing at the same time to mitigate the greenhouse effect.