Triggering solventogenesis by extracellular electrons: shifting carbon flow to butanol production by an electroactive Clostridium sp. in bioelectrochemical system
- Triggering solventogenesis by extracellular electrons: shifting carbon flow to butanol production by an electroactive Clostridium sp. in bioelectrochemical system
- 최옥경; 우한민; 엄영순
- Bioelectrochemical system; Clostridium; electroactive; solventogenesis
- Issue Date
- International Biotechnology Symposium and Exhibition
- The extracellular electron transfer from a cathode to microbes generates the reducing power in microorganisms under the bioelectrochemical system (BES). Here, we showed an electroactive Clostridium strain could directly use electrons from the cathode without any mediator. The electroactive Clostridium strain was cultivated in the cathode compartment poised at -160 mV vs. Ag/AgCl with P2 medium including 20 g/L glucose. The current was spontaneously increased according to the microbial growth and the current was 1,000 times higher in biofilm than in planktonic cells. The fact that the current was not shown in the supernatant suggested the direct electron transfer from the cathode to electroactive biofilms. The microscopy image showed the matrix of extracellular polysaccharide, pilus-like filaments and biofilm cells on the surface of cathode. Without electricity, the product of the Clostridium strain from glucose was mainly butyric acid. Even though the strain has butanol-synthesis pathway, only small amount of butanol was generated from glucose. We found the electron supplement by a cathode increased the ratio of NADH/NAD+ and triggered the solventogenesis. Finally, the butanol production was increased up to 2.5 times and its productivity was enhanced 2.1 times in BES. This study showed the shift of electrons to intensive NADH-consumption compound using direct electron transfer from the cathode to microorganisms and it could apply for electrofuel fermentation using electroactive Clostridium strain by electrochemically introduced reducing equivalent.
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