C4 Biofuel and High Value Biochemical Production Using Metabolically Engineered Clostridia

C4 biofuel and high value biochemical production using metabolically engineered clostridia

 

Morgan Bakies, Chao Ma and X Margaret Liu

In a world devoted to finding sources of clean energy, a sustainable, environmentally friendly fuel for motor vehicles is extremely important. Some clostridia, naturally occurring prokaryotes, have the potential to economically produce high energy biofuel in the form of butanol and/or high value biochemical such as butyric acid.  The goal of this research was to investigate the production of C4 bioproducts (butanol and butyric acid) using multiple clostridial strains including wild type and metabolically engineered mutants of C. tyrobutyricum.  First, the effect of the carbon and nitrogen sources in RCM and customized CGM media on cell growth and C4 production was evaluated.  Second, mini fermentations using serum bottles were performed to compare the C4 productivity from multiple engineered clostridia.  The wild type C. tyrobutyricum specializes in the synthesis of butyrate in an acidic environment, producing 1.9 g/L of butyric acid. The C. tyrobutyricum with knocked out ack gene (acetate kinase) raised butyric acid production to 7.7 g/L in serum bottle. The overexpression of aad gene (alcohol/aldehyde dehydrogenase) in C. tyrobutyricum ACKKO/pMAD 72 produced 3.2g/L of butanol and 6.3g/L of butyric acid.  Finally, this successful clostridial strain produced 33 g/L of butanol at pH 6.5 in the customized CGM medium. Further process development, for example pH and carbon source optimization, would metabolically shift carbon and energy flux to economically produce butanol and butyric acid.   

Contact information for abstract submission

Chao Ma: cma3@crimson.ua.edu

Margaret Liu: mliu@eng.ua.edu

The Department of Chemical and Biological Engineering

The University of Alabama

Tuscaloosa, AL 35405

(Phone): 205-348-0868