Citrulline deiminase pathway provides ATP and boosts growth of Clostridium carboxidivorans P7

Abstract

Abstract
Background Clostridium carboxidivorans P7 is capable of producing ethanol and butanol from inexpensive and non-food feedstock such as syngas. Achieving improved ethanol and butanol production in the strain for industrial application depends on the energetics and biomass, especially ATP availability. Results This study found that exogenous addition of citrulline promoted accumulation of ATP, increased specific growth rate, and reduced the doubling time of C. carboxidivorans P7. In heterotrophic fermentation experiments, the addition of citrulline increased intracellular ATP by 3.39-fold, significantly enhancing the production of total alcohol (ethanol + butanol) by 20%. Moreover, in the syngas fermentation experiments, the addition of citrulline improved the level of intracellular ATP and the biomass by 80.5% and 31.6%, respectively, resulting in a 18.6% and 60.3%, increased in ethanol and the alcohol/acid production ratio, respectively. Conclusions This is the first report that citrulline could promote the growth of C. carboxidivorans P7 and increased the level of intracellular ATP, which is of great significance for the use of C. carboxidivorans P7 to synthesize biofuels.