(516a) Discovery and Manipulation of a Native Polyketides Influencing ABE Production in Clostridium Acetobutylicum. 

The production of ABE (acetone, butanol, ethanol) by the anaerobic bacteria Clostridium is a bioprocess capable of converting various renewable substrates into high value solvents and fuels. Clostridium acetobutylicum ATCC 824 has long served as a model organism for clostridial ABE production, with an extensive body of literature ranging from fundamental cellular biology to industrial-scale fermentation. Despite the abundance of knowledge concerning this organism, the series of cellular events responsible for the dramatic and somewhat mysterious transition from acid- to solvent- production (deemed the â??metabolic switchâ?) remain unclear. Towards addressing this phenomena, we investigated a polyketide synthase (PKS) gene from C. acetobutylicum ATCC 824, which has previously been shown to be upregulated directly preceding the metabolic switch in ABE fermentation of this organism. Through targeted gene knockouts, HRMS-guided comparative metabolomics, and extensive structural characterization, we identified a previously undiscovered family of three polyketides synthesized by the PKS gene product. Batch fermentations of PKS-modified strains revealed that while the polyketides are not essential for the metabolic switch (and hence, ABE production), the presence or absence of these compounds could influence both the solvent titers and productivities of C. acetobutylicum. Through this work, we hope to highlight the potentially significant role of secondary metabolites in clostridial fermentations, and provide a relatively unexplored strategy for manipulating these industrially-relevant organisms.