Biofuels Production projects
Improving Clostridial Fermentation Performance by Signaling Molecules
Extracellular signaling small molecules (SSMs) are commonly used by bacteria to access information about both the intracellular physiological status and extracellular environment. These small molecules are critical in controlling complex biological processes including morphological differentiation, multicellularity, biofilm formation, virulence, motility, stress response, substrate usage, and secondary metabolite production. Despite the importance of SSMs In bacterial physiology and behavior, little is known about SSMs in clostridia. Although genomic analysis indicates the presence of SSMs in this genus, little work has been done to experimentally investigate these molecules. In order to improve the performance of clostridial ABE fermentation, it is crucial to unveil the identity and function of hidden SSMs in relevant Clostridium species. The governing hypothesis of this proposal is that SSMs can be used to manipulate clostridial fermentations by controlling cell density, cellular development, substrate usage, solvent production, and solvent tolerance. This project will use comprehensive approaches: activity-based profiling and targeted genome mining to unveil SSMs of clostridia, with the goal of improving ABE fermentation performance. In addition, common bacterial pheromones, especially those involved in morphological differentiation and the initiation of secondary metabolite production, will be applied to clostridial cultures to probe the possible beneficial effects of heterogenous SSMs on ABE fermentation.
The production of ABE (acetone, butanol, ethanol) by the anaerobic bacteria Clostridium is a promising process capable of converting various renewable substrates into high-value fuels. We hypothesize that some secondary metabolites produced by Clostridium regulate processes related to solvent production, and that large-scale fermentations may be improved by manipulating these small molecules. We have established a gene knockout system in Clostridium acetobutylicum and disrupted a polyketide synthase gene which was upregulated just prior to entering the solventogenic phase. Preliminary results have also been obtained in identifying quorum sensing cyclic peptides and relevant UV active secondary metabolites from C. saccharoperbutylacetonicum strain N1-4. In addition, semi-continuous fermentations have been performed and the role of clostridial signaling in inducing ABE production has been suggested. While most efforts on improving large-scale fermentations have focused on optimizing fermentation conditions and solvent separation, our project underlines the importance of microbial signaling to complement these approaches.