Metabolic Engineering Of C. Tyrobutyricum To Improve Biofuel Production By Boosting Reducing Power

Metabolic engineering of Clostridium tyrobutyricum to improve biofuel production by boosting reducing power

Brittany Artale, Chao Ma, and Margaret Liu

Biobutanol (C4 bioenergy) and biobutyric acid (C4 biochemical) can be produced by metabolically engineered Clostridium tyrobutyricum. Rebalancing carbon between C4 products has been applied to generate C. tyrobutyricum-adhE2 that produces biobutanol and butyric acid in previous research. However, the unbalanced redox (NADH) and toxic byproduct from biomass hydrolysate have hindered further improving butanol production. In this study, both medium optimization and metabolic engineering were performed to increase reducing power and detoxify hydrolysate but not adversely affect cell growth. Specifically, five of the ten evaluated medium components have been identified to improve butanol titer by 30%, from 8.5 g/L to 11.5 g/L in serum bottle cultures, and carbon and redox were rebalanced by some components. In addition, one mutant, C. tyrobutyricum-aad, favoring C2 bioenergy (i.e. ethanol) production over butanol was constructed as a negative control. The enzyme enabling a new metabolic pathway to produce NADH is being introduced to C. tyrobutyricum-adhE2, C. tyrobutyricum-aad and wild type strains to further rebalance redox. This study showed that the integration of medium optimization and metabolic engineering is a powerful tool to regulate metabolism and, therefore, improve biobutanol production.

Authors:

Brittany Artale

Department of Chemical Engineering

The University of New Hampshire

Durham, NH 03824

(Email): bax49@wildcats.unh.edu

(Phone): 806-908-5245

Chao Ma

Department of Chemical and Biological Engineering

The University of Alabama

301 7^th Avenue, Hauser Hall R116

Tuscaloosa, AL 35405

(Email): cma3@crimson.ua.edu

(Phone): 205-292-8115

Margaret Liu, PhD

Assistant Professor

Department of Chemical and Biological Engineering

The University of Alabama

301 7^th Avenue, Hauser Hall R116

Tuscaloosa, AL 35405

(Email): mliu@eng.ua.edu

(Phone): 205-348-0868