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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.
The green microalga Haematococcus pluvialis accumulates astaxanthin, a potent antioxidant pigment, as a defense mechanism against environmental stresses. In this study, we investigated the technical feasibility of a stress-based method for inducing astaxanthin biosynthesis in H. pluvialis using electric stimulation in a two-chamber bioelectrochemical system. When a cathodic (reduction) current of 3 mA (voltage: 2 V) was applied to H. pluvialis cells for two days, considerable lysis and breakage of algal cells were observed, possibly owing to the formation of excess reactive oxygen species at the cathode. Conversely, in the absence of cell breakage, the application of anodic (oxidation) current effectively stimulated astaxanthin biosynthesis at a voltage range of 2–6 V, whereas the same could not be induced in the untreated control. At an optimal voltage of 4 V (anodic current: 30 mA), the astaxanthin content in the cells electro-treated for 2 h was 36.9% higher than that in untreated cells. Our findings suggest that electric treatment can be used to improve astaxanthin production in H. pluvialis culture if bioelectrochemical parameters, such as electric strength and duration, are regulated properly.
Hana-Nur Fitriana; Soo-Youn Lee; Sun-A Choi; Ji-Ye Lee; Bo-Lam Kim; Jin-Suk Lee; You-Kwan Oh. Electric Stimulation of Astaxanthin Biosynthesis in Haematococcus pluvialis. Applied Sciences 2021, 11, 3348 .
AMA StyleHana-Nur Fitriana, Soo-Youn Lee, Sun-A Choi, Ji-Ye Lee, Bo-Lam Kim, Jin-Suk Lee, You-Kwan Oh. Electric Stimulation of Astaxanthin Biosynthesis in Haematococcus pluvialis. Applied Sciences. 2021; 11 (8):3348.
Chicago/Turabian StyleHana-Nur Fitriana; Soo-Youn Lee; Sun-A Choi; Ji-Ye Lee; Bo-Lam Kim; Jin-Suk Lee; You-Kwan Oh. 2021. "Electric Stimulation of Astaxanthin Biosynthesis in Haematococcus pluvialis." Applied Sciences 11, no. 8: 3348.
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.
Haematococcus pluvialis accumulates astaxanthin, which is a high-value antioxidant, during the red cyst stage of its lifecycle. The development of a rigid cell wall in the cysts hinders the recovery of astaxanthin. We investigated morphological changes and cell disruption of mature H. pluvialis cyst cells while using high-pressure homogenization for astaxanthin extraction. When treated with French-press-cell (pressure, 10,000–30,000 psi; passage, 1–3), the intact cyst cells were significantly broken or fully ruptured, releasing cytoplasmic components, thereby facilitating the separation of astaxanthin by ethyl acetate. Fluorescence microscopy observations using three different fluorescent dyes revealed that a greater degree of cell breakage caused greater external dispersion of astaxanthin, chlorophyll, lipids, proteins, and carbohydrates. The mechanical treatment resulted in a high cell disruption rate of up to 91% based on microscopic cell typing and Coulter methods. After the ethyl acetate extraction, the astaxanthin concentration significantly increased by 15.2 mg/L in proportion to the increase in cell disruption rate, which indicates that cell disruption is a critical factor for solvent-based astaxanthin recovery. Furthermore, this study recommends a synergistic combination of the fast instrumental particle-volume-distribution analysis and microscope-based morphologic phenotyping for the development of practical H. pluvialis biorefinery processes that co-produce various biological products, including lipids, proteins, carbohydrates, chlorophyll, and astaxanthin.
Ramasamy Praveenkumar; Jiye Lee; Durairaj Vijayan; Soo Youn Lee; Kyubock Lee; Sang Jun Sim; Min Eui Hong; Young-Eun Kim; You-Kwan Oh. Morphological Change and Cell Disruption of Haematococcus pluvialis Cyst during High-Pressure Homogenization for Astaxanthin Recovery. Applied Sciences 2020, 10, 513 .
AMA StyleRamasamy Praveenkumar, Jiye Lee, Durairaj Vijayan, Soo Youn Lee, Kyubock Lee, Sang Jun Sim, Min Eui Hong, Young-Eun Kim, You-Kwan Oh. Morphological Change and Cell Disruption of Haematococcus pluvialis Cyst during High-Pressure Homogenization for Astaxanthin Recovery. Applied Sciences. 2020; 10 (2):513.
Chicago/Turabian StyleRamasamy Praveenkumar; Jiye Lee; Durairaj Vijayan; Soo Youn Lee; Kyubock Lee; Sang Jun Sim; Min Eui Hong; Young-Eun Kim; You-Kwan Oh. 2020. "Morphological Change and Cell Disruption of Haematococcus pluvialis Cyst during High-Pressure Homogenization for Astaxanthin Recovery." Applied Sciences 10, no. 2: 513.
This work studied Gram-positive and weak electricigen Corynebacterium glutamicum for its ability to transfer electrons and to produce bioelectricity in microbial fuel cells (MFCs). The electrochemical and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) results revealed that C. glutamicum had the potential to mediate electron transfer to an electrode by emitting its own extracellular electron shuttles such as flavins. To enhance the current collection from C. glutamicum, a carbon cloth anode was modified with ferrocene-branched chitosan hydrogel (redox-hydrogel). The maximum current density of the ferrocene-branched chitosan redox hydrogel anode with C. glutamicum was drastically increased to 120 µA cm−2 relative to a bare carbon cloth electrode with C. glutamicum (261 nA cm−2). The power density and polarization curves for the MFC operation with the redox-hydrogel-modified anode showed that C. glutamicum effectively generated bioelectricity by means of the redox-hydrogel anode. The results suggest that, in such an electro-fermentation process, ferrocene-branched chitosan hydrogel grafted onto an anode surface would also facilitate both electron transfer from C. glutamicum to the anode and bioelectricity generation.
Soo Youn Lee; Jiho Min; Sangmin Lee; Hana Nur Fitriana; Min-Sik Kim; Gwon Woo Park; Jin-Suk Lee. Bioelectricity Generation by Corynebacterium glutamicum with Redox-Hydrogel-Modified Carbon Electrode. Applied Sciences 2019, 9, 4251 .
AMA StyleSoo Youn Lee, Jiho Min, Sangmin Lee, Hana Nur Fitriana, Min-Sik Kim, Gwon Woo Park, Jin-Suk Lee. Bioelectricity Generation by Corynebacterium glutamicum with Redox-Hydrogel-Modified Carbon Electrode. Applied Sciences. 2019; 9 (20):4251.
Chicago/Turabian StyleSoo Youn Lee; Jiho Min; Sangmin Lee; Hana Nur Fitriana; Min-Sik Kim; Gwon Woo Park; Jin-Suk Lee. 2019. "Bioelectricity Generation by Corynebacterium glutamicum with Redox-Hydrogel-Modified Carbon Electrode." Applied Sciences 9, no. 20: 4251.