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Engineering acetogenic Clostridia for ethanol and n-butanol production from CO2

Research Scholar

Chih-Chin Chen, Chemical and Biomolecular Engineering (Taiwan)
Shang-Tian Yang
, Faculty Mentor


Chih-Chin Chen is a postdoctoral researcher in Shang-Tian Yang's group in the William G. Lowrie Department of Chemical & Biomolecular Engineering at The Ohio State University, working on “Engineering acetogenic Clostridia for ethanol and n-butanol production from CO2.” Chen received her PhD in microbial genetics from Gonville and Caius College, University of Cambridge in 2010, her master's degree from National Tsing Hua University in 2003 and her bachelor's degree in public health from Taipei Medical University in 2001.

What is the issue or problem addressed in your research?

Butanol is an important industrial solvent and potentially a better transportation fuel than ethanol. Currently, butanol is almost exclusively produced via petrochemical routes. Biobutanol will have a great potential to compete with ethanol as a transportation fuel when its production cost is reduced by using advanced fermentation technologies such as metabolically engineered Clostridia mutants.

Some Clostridia, including C. ljungdahlii and C. carboxidivorans, are capable of producing ethanol and butanol from CO2 and H2. However, the alcohol productivity, yield, and titer from these native strains are low and uneconomical for industrial applications. In contrast, several acetogenic Clostridia can convert CO2 and H2 to acetate with high yield, titer, and productivity comparable to those from glucose as the substrate. A high metabolic flux from CO2 to acetyl-CoA, the immediate precursor for both acetate and ethanol, is the prerequisite for developing a highly productive ethanol and butanol producers.

What methodology did you use in your research?

In this work, we engineered homoacetogens for ethanol and n-butanol production by introducing aldehyde/alcohol dehydrogenase and genes in the acetyl-CoA to butyryl-CoA pathway using modular clostridia plasmids. The fermentation kinetics of these engineered mutants and their ability to produce ethanol and butanol from CO2 and H2 were studied.

What are the purpose/rationale and implications of your research?

This research is concerning the development of metabolically engineered Clostridia bacteria for production of biofuels from CO2 that can benefit US energy industries. Specifically, novel fermentation processes using metabolically engineered mutants will be developed to produce biobutanol, a better biofuel than ethanol, from CO2. The abundant inexpensive renewable bioresources can be used to produce butanol economically by means of the proposed processes, adding value to biorefinery byproducts and simultaneously solving green house gas (CO2) emission problems. Currently, bioethanol is the major biofuel on the market. However, biobutanol has attracted a lot of attention for its potential as a transportation fuel mainly because butanol has many desirable characteristics that make it a better fuel than ethanol. Currently, butanol is almost exclusively produced via petrochemical routes and used mainly in chemical and solvent markets at a price of more than ~$6.75 per gallon and with a worldwide market of ~1.4 billion gallons per year.