Ralstonia eutropha Strain H16 as Model Organism for PHA Metabolism and for Biotechnological Production of Technically Interesting Biopolymers

The Gram-negative, facultative chemolithoautotrophic bacterium Ralstonia eutropha has been intensively investigated for almost 50 years. Today it is the best studied ‘Knallgas’ bacterium and producer of poly(3-hydroxybutyric acid). This polyester provides the basis for renewable resource-based biodegradable plastic materials and has attracted much biotechnological interest. The polymer is accumulated in large amounts in the cell and can be used for various applications ranging from replacement of fossil resource-based bulk plastics to high-value special purpose polymers. To further enhance productivity and to allow tailormade poly(hydroxyalkanoic acids) (PHA) with different monomer compositions by metabolic engineering, the knowledge of metabolic pathways and of the biochemical properties of the enzymes involved is essential. Furthermore, proteins covering the PHA granule surface, which are referred to as phasins, and fusions of these phasins to other proteins are promising candidates for various protein technologies. The recently published genome sequence of strain H16 allows researchers to take a closer look at the genetic potential of this versatile bacterium. R. eutropha is, however, not limited to PHAs and to PHA-related polymers like poly(mercaptoalkanoic acids) as it can also be employed for production of a range of other interesting polymers including polyamides like cyanophycin.