Researchers have uncovered the complex interdependence and orchestration of metabolic reactions, gene regulation, and environmental cues of clostridial metabolism. Ting Lu, an assistant professor of bioengineering at the University of Illinois at Urbana-Champaign led the team in providing new insights for advanced biofuel development.

Lu explained, “This work advances our fundamental understanding of the complex, system-level process of clostridial acetone-butanol-ethanol (ABE) fermentation. Simultaneously, it provides a powerful tool for guiding strain design and protocol optimization, therefore facilitating the development of next-generation biofuels.”

Clostridium Acetobutylicum.  Image Credit: Public Domain from Wikipedia.

Clostridium Acetobutylicum. Image Credit: Public Domain from Wikipedia.

Microbial metabolism is a means by which a microbe uses nutrients and generates energy to live and reproduce. It typically involves complex biochemical processes implemented through the orchestration of metabolic reactions and gene regulation, as well as their interactions with environmental cues. One canonical example is the ABE fermentation by Clostridium acetobutylicum, during which cells convert carbon sources to organic acids that are later re-assimilated to produce solvents as a strategy for cellular survival.

Lu, who is also affiliated with the Department of Physics and Carl R. Woese Institute for Genomic Biology at Illinois set ups the background with, “Clostridium is very much like a factory during fermentation which converts carbon sources into renewable, advanced biofuels that can be directly used to fuel your car. The complexity and systems nature of the process have been largely underappreciated, rendering challenges in understanding and optimizing solvent (ABE) production.”

Chen Liao, a bioengineering graduate student and first author of their study paper said, “In this study, we developed an integrated computational framework for the analysis and exploitation of the solvent metabolism by C. acetobutylicum.”

The paper, “Integrated, Systems Metabolic Picture of Acetone-Butanol-Ethanol Fermentation by Clostridium acetobutylicum,” has been published in the Proceedings of the National Academy of Sciences of the United States of America.

Lu sums the work up, “To our knowledge, this framework elucidates, for the first time, the complex system-level orchestration of metabolic reactions, gene regulation, and environmental cues during clostridial ABE fermentation. It also provides a quantitative tool for generating new hypotheses and for guiding strain design and protocol optimization – invaluable for the development of efficient metabolic engineering strategies, expediting the development of advanced biofuels. More broadly, by using the ABE fermentation as an example, the work further sheds light on systems biology toward an integrated and quantitative understanding of complex microbial physiology.”

Lu sums up academically. In other more mainstream words the team has reached a milestone in bacteria research by providing an activity map that one can expect will have a huge impact over time in producing much more acetone, butanol and ethanol.

For now most ethanol is produced using processes that convert the plant starches to sugars that are then fed to yeasts rather than bacteria. Clostridium acetobutylicum is attractive because of the production split of 3 parts acetone to 6 parts butanol and only one of ethanol. The bacterial process also begins using the plant starches skipping an entire step of converting to sugars.

Research progress is already underway with some modified bacteria showing promise. The Illinois team has reached a milestone providing gene designers a new tool to accelerate the development of better bacteria for commercial applications and likely a much increased supply of renewable fuels that are much closer to “drop in gasoline” replacements.


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