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Polyhydroxyalkanoates (PHA) are a class of biopolymers with interesting material properties and highly beneficial use in certain applications. This is the base for its market presence with a prospective increasing share over a long period. Biotechnological production with prokaryotes is, undoubtedly, the most promising way to go and may remain so for the near future. Regarding the use of substrates, three general strategies can be identified, similar to biorefinery concepts: (1) using sugar or starch as input (first-generation substrates), (2) using lignocellulosic biomass or other liquid and solid organic residues (waste streams) as input (second-generation substrates), and (3) biotechnology with photo- and autotrophic bacteria – using CO2 and sunlight as input (third-generation substrates). With a closer look at cell physiologies, the conversion yields, and the overall technological effort, the specific advantages and disadvantages of each of those strategies are made clear through comparison. This chapter focuses on the critical parameters of a phototrophic PHA production with cyanobacteria and direct output compared with some of the established biotechnological processes. It concludes with a look at the required research and process optimization for the near future and, finally, discusses the scenario of a possible long-term PHA (and PHB) production strategy. |
