Towards increased microalgal productivity in photobioreactors

Currently there is much interest to cultivate microalgae for the production of bulk products like lipids for biodiesel or as feedstock for industrial chemical processes. To make the production economically feasible, it is essential to develop cultivation systems in which algae convert the light with a high photosynthetic efficiency, to obtain microalgae with specific production characteristics, to optimize the culture medium, to develop cheap harvesting methods and finally professionals to implement and develop the technology. For the development of better algal cultivation systems, insight is needed on the efficiency of light conversion by these algae. Two concepts of light dilution in photobioreactor design are presented to reflect how potentially higher photosynthetic efficiencies can be achieved. Also, fast screening methods for microalgae are discussed, which can be applied to select strains with better production characteristics, to optimize the medium, to compare cultivation conditions and to investigate the toxic effects of chemicals. Apart from obtaining enhanced algal productivities a low-cost harvesting process is required. For harvesting of bulk products, as preconcentration step, controlled auto-flocculation is worthwhile investigating. Beside these research lines, more and better education for biochemical engineers should be developed to push microalgal biotechnology ahead.