Suspension culture of microorganisms (Algae and Cyanobacteria) under phototrophic conditions
Global net primary production of biomass has faded dramatically over the past few decades as a consequence of the increasing population and its infrastructure demands. Photosynthetic microorganisms constitute the substructure of the water based food chain and are characterized by a five-to tenfold higher surface area productivity in comparison to traditional terrestrial crops. Based on their larger areal productivity they are an expandable and so far sparsely utilized resource in terms of biotechnology. In addition, extended utilization in a sustainable form decreases anthropogenic carbon dioxide emission. Furthermore, the production of valuable compounds, for example, for pharmaceutical and cosmetically applications without genetic modification, is broadly possible by simple modification of cultivation parameters. For application of these benefits to the preservation of the livelihood of mankind, sustainable (phototrophic) production and utilization paths need to be designed beyond arable land use for food production. The present chapter describes the basics of microalgal biology as well as basic and advanced process design aspects. Industrially relevant open and closed cultivation systems, namely, open ponds and photobioreactors, are elucidated and compared in terms of design, costs, and process stability as well as performance, energy consumption, and potential products. The conclusion gives an overview of prospects and future challenges.