Development of a Highly Efficient Gene Delivery System for Syngas Fermenting Clostridia

Gabriele Philipps, Sebastian de Vries, Christian Janke, Nicole Schnaß and Stefan Jennewein

Department of Industrial Biotechnology, Fraunhofer Institute for Molecular Biology and Applied Ecology, Aachen, Germany

Several microorganisms belonging to the genus Clostridia can convert synthesis gas (syngas), a mixture of carbon monoxide, carbon dioxide and hydrogen, into more complex organic molecules, including biomass, acetate and ethanol. The conversion of syngas into ethanol is particularly relevant in the context of biofuel production, and several start-up companies are already pursuing this technology. The commercial development of syngas-based ethanol fermentation processes is challenging because additional energy is needed to purify the resulting alcohols by distillation. Based on the known metabolic capabilities of different Clostridium strains, we can already envision the production of several other chemicals and biofuels, most representing high-value products that cannot be synthesized via established chemical routes such as the Fischer-Tropsch process.

However, for the establishment of these biosynthetic pathways (beyond syngas based ethanol production) metabolic engineering approaches involving complex pathways become necessary. Up to today the metabolic engineering of Costridia in general and of syngas fermenting Clostridia strains in particular proved rather challenging.

We developed a highly efficient gene delivery system capable for introducing complex (large) gene clusters encoding entire biosynthetic pathways into syngas fermenting Clostidia such as C. ljungdahlii and C. autoethanogenum. This development will not only deliver syngas-based fermentation systems for chemicals and biofuels but will also foster the development of further Clostridia fermentation processes using other feed stocks such as cellulose (e.g. by Clostridia cellulolyticum).