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Microbial electrosynthesis (MES) is a promising technology platform for the production of chemicals and fuels from CO2 and external conducting materials (i.e., electrodes). In this system, electroactive microorganisms, called electrotrophs, serve as biocatalysts for cathodic reaction. While several CO2-fixing microorganisms can reduce CO2 to a variety of organic compounds by utilizing electricity as reducing energy, direct extracellular electron uptake is indispensable to achieve highly energy-efficient reaction. In the work reported here, Rhodobacter sphaeroides, a CO2-fixing chemoautotroph and a potential electroactive bacterium, was adopted to perform a cathodic CO2 reduction reaction via MES. To promote direct electron uptake, the graphite felt cathode was modified with a combination of chitosan and carbodiimide compound. Robust biofilm formation promoted by amide functionality between R. sphaeroides and a graphite felt cathode showed significantly higher faradaic efficiency (98.0%) for coulomb to biomass and succinic acid production than those of the bare (34%) and chitosan-modified graphite cathode (77.8%), respectively. The results suggest that cathode modification using a chitosan/carbodiimide composite may facilitate electron utilization by improving direct contact between an electrode and R. sphaeroides.
Hana Nur Fitriana; Jiye Lee; Sangmin Lee; Myounghoon Moon; Yu Rim Lee; You-Kwan Oh; Myeonghwa Park; Jin-Suk Lee; Jinju Song; Soo Youn Lee. Surface Modification of a Graphite Felt Cathode with Amide-Coupling Enhances the Electron Uptake of Rhodobacter sphaeroides. Applied Sciences 2021, 11, 7585 .
AMA StyleHana Nur Fitriana, Jiye Lee, Sangmin Lee, Myounghoon Moon, Yu Rim Lee, You-Kwan Oh, Myeonghwa Park, Jin-Suk Lee, Jinju Song, Soo Youn Lee. Surface Modification of a Graphite Felt Cathode with Amide-Coupling Enhances the Electron Uptake of Rhodobacter sphaeroides. Applied Sciences. 2021; 11 (16):7585.
Chicago/Turabian StyleHana Nur Fitriana; Jiye Lee; Sangmin Lee; Myounghoon Moon; Yu Rim Lee; You-Kwan Oh; Myeonghwa Park; Jin-Suk Lee; Jinju Song; Soo Youn Lee. 2021. "Surface Modification of a Graphite Felt Cathode with Amide-Coupling Enhances the Electron Uptake of Rhodobacter sphaeroides." Applied Sciences 11, no. 16: 7585.
In the recent climate change regime, industrial demand for renewable materials to replace petroleum-derived polymers continues to rise. Of particular interest is polyhydroxybutyrate (PHB) as a substitute for polypropylene. Accumulating evidence indicates that PHB is highly produced as a carbon storage material in various microorganisms. The effects of growth conditions on PHB production have been widely studied in chemolithotrophs, particularly in Rhodobacter. However, the results on PHB production in Rhodobacter have been somewhat inconsistent due to different strains and experimental conditions, and it is currently unclear how diverse environmental factors are linked with PHB production. Here, we report optimized growth conditions for PHB production and show that the growth conditions are closely related to reactive oxygen species (ROS) regulation. PHB accumulates in cells up to approximately 50% at the highest level under dark-aerobic conditions as opposed to light aerobic/anaerobic conditions. According to the time-course, PHB contents increased at 48 h and then gradually decreased. When observing the effect of temperature and medium composition on PHB production, 30 °C and a carbon/nitrogen ratio of 9:1 or more were found to be most effective. Among PHB biosynthetic genes, PhaA and PhaB are highly correlated with PHB production, whereas PhaC and PhaZ showed little change in overall expression levels. We found that, while the amount of hydrogen peroxide in cells under dark conditions was relatively low compared to the light conditions, peroxidase activities and expression levels of antioxidant-related genes were high. These observations suggest optimal culture conditions for growth and PHB production and the importance of ROS-scavenging signaling with regard to PHB production.
Yu Rim Lee; Hana Nur Fitriana; Soo Youn Lee; Min-Sik Kim; Myounghoon Moon; Won-Heong Lee; Jin-Suk Lee; Sangmin Lee. Molecular Profiling and Optimization Studies for Growth and PHB Production Conditions in Rhodobacter sphaeroides. Energies 2020, 13, 6471 .
AMA StyleYu Rim Lee, Hana Nur Fitriana, Soo Youn Lee, Min-Sik Kim, Myounghoon Moon, Won-Heong Lee, Jin-Suk Lee, Sangmin Lee. Molecular Profiling and Optimization Studies for Growth and PHB Production Conditions in Rhodobacter sphaeroides. Energies. 2020; 13 (23):6471.
Chicago/Turabian StyleYu Rim Lee; Hana Nur Fitriana; Soo Youn Lee; Min-Sik Kim; Myounghoon Moon; Won-Heong Lee; Jin-Suk Lee; Sangmin Lee. 2020. "Molecular Profiling and Optimization Studies for Growth and PHB Production Conditions in Rhodobacter sphaeroides." Energies 13, no. 23: 6471.