Enhancing carbohydrate productivity in photosynthetic microorganism production: A comparison between cyanobacteria and microalgae and the effect of cultivation systems

Photosynthetic microorganisms have received enormous attention due to their fast growth rate, higher photosynthetic efficiency (PE) and productivity, and high carbohydrates content (up to 50% DW). Microalgae and cyanobacteria are the organisms investigated, but some differences should be discussed between them, regarding carbohydrates composition, light utilization, growth rates, and biomass productivity. The common batch method to evaluate growth capabilities is strongly limited by a number of factors, such as the acclimation of preinoculum and a changing biomass concentration over time, which makes it more difficult to explain the results. Conversely, in a continuous system operated at a steady state, biomass production is constant and is well acclimated to the reactor adapting to environmental conditions. In this chapter, a brief comparison between cyanobacteria and microalgae based on composition, productivity, and PE is completed and the effectiveness of the continuous system as a method to exploit these organisms for carbohydrate production.