Molecular insights into transcriptional regulation for the optimisation of butanol-producing clostridia.

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In the early 20th century, industrial production of acetone and butanol relied on large scale microbial fermentations carried out by solvent producing members of the genus Clostridium. Today this classical 'AB fermentation' process is no longer economically viable. Thus, it is important to improve the organisms' performance through metabolic engineering, aiming at increasing butanol titres, yields and productivity. However, decisive breakthroughs are yet to be made in order to establish a sustainable production of biofuels and chemicals through this route. The strain Clostridium acetobutylicum is of particular interest for genetic engineering, but a better understanding of the organisms' physiology, in particular the mechanisms that govern timing and extent of solvent formation is required. Bacterial communication mechanisms play a crucial role in butanol and acetone formation and novel transcriptional regulators of the RRNPP family have been identified as being an important part of this system. The overall objective of this project is to investigate the molecular basis of the transcriptional regulator's mode of action in order to engineer high performance butanol producing strains using structural biology, protein engineering, biochemistry, microbiology and genetic engineering techniques. Inactivation of this regulator almost completely abolishes the formation of both acetone and butanol. The protein appears to be inactive when cells are actively growing but adopts an active state when the bacteria enter stationary phase and begin to produce solvents. A detailed understanding of the underlying molecular mechanism will greatly facilitate successful engineering of improved solvent producing strains. In addition, as homologues of this regulator are also present in all species of the genus Clostridium, including its pathogenic members, novel insights into how organisms operate that cause diarrhoea, tetanus and botulism will also be gained.