Carbon dioxide consumption of the microalga Scenedesmus obtusiusculus under transient inlet CO concentration variations.

The extensive microalgae diversity offers considerable versatility for a wide range of biotechnological applications in environmental and production processes. Microalgal cultivation is based on CO fixation via photosynthesis and, consequently, it is necessary to evaluate, in a short time and reliable way, the effect of the CO gas concentration on the consumption rate and establish the tolerance range of different strains and the amount of inorganic carbon that can be incorporated into biomass in order to establish the potential for industrial scale application. Dynamic experiments allow calculating the short-term microalgal photosynthetic activity of strains in photobioreactors. In this paper, the effect of step-changes in CO concentration fed to a 20L bubble column photobioreactor on the CO consumption rate of Scenedesmus obtusiusculus was evaluated at different operation times. The highest apparent CO consumption rate (336μmolms and 5.6% of CO) was 6530mggd and it decreased to 222mggd when biomass concentration increased of 0.5 to 3.1gL and 5.6% of CO was fed. For low CO concentrations (<3.8%) the pH remained close to the optimal value (7.5 and 8). The CO consumption rates show that S. obtusiusculus was not limited by CO availability for concentrations above of 3.8%. The CO mass balance showed that 90% of the C-CO transferred was used for S. obtusiusculus growth.