Abstract
BackgroundClostridium 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.ResultsThis 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 an 18.6% and 60.3% increase in ethanol and the alcohol/acid production ratio, respectively.ConclusionsThis is the first report that citrulline could promote the growth of C. carboxidivorans P7 and increase the level of intracellular ATP, which is of great significance for the use of C. carboxidivorans P7 to synthesize biofuels.
Highlights
Clostridium carboxidivorans P7 is capable of producing ethanol and butanol from inexpensive and non-food feedstock, such as syngas
The results indicated that the addition of citrulline significantly promoted the growth capacity of C. carboxidivorans P7, and the maximum O D600 increased by 18.6% compared with the wild-type strain (Fig. 1A)
The WLP pathway exists in C. carboxidivorans P7, which has been found in most acetic bacteria, such as Acetobacterium woodii [28], Clostridium formicoaceticum [29], Clostridium aceticum [30], Clostridium ljungdahlii [31], and C. autoethanogenum [32]
Summary
Clostridium carboxidivorans P7 is capable of producing ethanol and butanol from inexpensive and non-food feedstock, such as syngas. Clostridium carboxidivorans P7 is one of the strains capable of producing biofuel from syngas [16]. It can synthesize ethanol and n-butanol by capturing C O2, CO, and H2 through WLP (Wood–Ljungdahl pathway) [17, 18]. There is an urgent need to enhance intracellular ATP supply and biomass of C. carboxidivorans P7, so as to promote the biofuels production. The addition of arginine shortened the Clostridium autoethanogenum doubling time, increased the intracellular ATP energy level by fivefold, and weakened the accumulation of by-product acetic acid [15]. Amino acid metabolism has an enormous potential to improve the cell density and intracellular energy level of C. carboxidivorans P7
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