Ralstonia eutropha H16 in progress: Applications beside PHAs and establishment as production platform by advanced genetic tools

Abstract

Ralstonia eutropha strain H16 is a Gram-negative non-pathogenic betaproteobacterium ubiquitously found in soils and has been the subject of intensive research for more than 50 years. Due to its remarkable metabolically versatility, it utilizes a broad range of renewable heterotrophic resources. The substrate utilization range can be further extended by metabolic engineering as genetic tools are available. It has become the best studied "Knallgas" bacterium capable of chemolithoautotrophic growth with hydrogen as the electron donor and carbon dioxide as the carbon source. It also serves as a model organism to study the metabolism of poly(β-hydroxybutyrate), a polyester which is accumulated within the cells for storage of both carbon and energy. Thermoplastic and biodegradable properties of this polyhydroxyalkanoate (PHA) have attracted much biotechnical interest as a replacement for fossil resource-based plastics. The first applications of R. eutropha aimed at chemolithoautotrophic production of single cell protein (SCP) for food and feed and the synthesis of various PHAs. The complete annotated genome is available allowing systematic biology approaches together with data provided by available omics studies. Besides PHAs, novel biopolymers of 2-hydroxyalkanoates and polythioesters or cyanophycin as well as chemicals such as alcohols, alkanes, alkenes, and further interesting value added chemicals significantly recently extended the range of products synthesized by R. eutropha. High cell density cultivations can be performed without too much effort and the available repertoire of genetic tools is rapidly growing. Altogether, this qualifies R. eutropha strain H16 to become a production platform strain for a large spectrum of products.

Keywords: Ralstonia eutropha H16; genetic tools; metabolic engineering; production platform; value added chemicals.