Interdisciplinary Graduate Programs Symposium
2014 OSU Molecular Life Sciences
Interdisciplinary Graduate Programs Symposium
|
|
|
|
|
Poster abstracts
Abstract:
Clostridium tyrobutyricum ATCC 25755 is an acidogen with butyrate and acetate as the two main fermentation products from glucose and xylose. In addition to a high butyrate yield, C. tyrobutyricum also has a high butyrate and butanol tolerance, making it an ideal candidate for the industrial production of biofuels such as n-butanol. In a previous study, an adhE2 gene encoding a bifunctional aldehyde/alcohol dehydrogenase from C. acetobutylicum was overexpressed in an ack knock-out strain of C. tyrobutyricum, and the mutant produced 10 g/L butanol and more than 15 g/L acids from glucose. To further improve butanol production, it is desirable to re-utilize the butyrate and acetate and convert them to their corresponding alcohols. In this study, three different plasmids containing ctfAB genes which encode for a CoA-transferase from Clostridium acetobutylicum were constructed. The CoA-transferase catalyzing the formation of acetoacetate by transferring a CoA moiety from acetoacetyl-CoA to either butyrate or acetate was co-expressed with the adhE2 gene. As expected, ctfAB overexpression raised butanol production to 12-14 g/L, with an enhanced butanol yield (from 0.10 g/g to 0.26 g/g glucose) and productivity (from 0.13 g/L•h to 0.35 g/L•h), and reduced butyrate and acetate accumulation by 80% and 57%, respectively. Interestingly, ctfAB overexpression also induced acetone production to a level of 4-7.5 g/L. Batch fermentation kinetics in pH-controlled fermentors with these mutants was further investigated at different pH values, and the results are presented in this study.
Keywords: Butanol, Clostridium tyrobutyricum, CoA-transferase
