(664b) Improve Biobutanol Production By Integrated Carbon and Redox Rebalance in Clostridium Tyrobutyricum

Biobutanol is a promising renewable alternative to gasoline because of its high energy content and compatibility with existing engines. The acidogenic Clostridium tyrobutyricum, with high butanol tolerance, has been metabolically engineered to produce a high level biobutanol. In this study the wild type C. tyrobutyricum was used as a model host to evaluate the effect of rebalancing carbon and redox on butanol production. The metabolic cell engineering was performed to introduce carbon redistribution gene, i.e. aldehyde/alcohol dehydrogenase (adhE2), and overexpress the redox rebalance genes, i.e. NAD⁺-dependent pyruvate dehydrogenase (pdh) and formate dehydrogenase (fdh), using double vector expression system. The serum bottle cultures showed that butanol titer was increased to 2.7 g/L by C. tyrobutyricum-adhE2/fdh and 2.1 g/L by C. tyrobutyricum-adhE2/pdh from 1.0 g/L by C. tyrobutyricum-adhE2. These results demonstrated that the boost of NADH could improve butanol production. To achieve high butanol production, the single vector expression system is being constructed to engineer the high butyrate producing C. tyrobutyricum strain. The finding in this study also indicated that the butanol could be improved by rebalancing redox via metabolic process engineering.