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Microbial lipid production from oleaginous yeasts is a promising process for the sustainable development of the microbial biodiesel industry. However, the feedstock cost poses an economic problem for the production of microbial biodiesel. After lipid extraction, yeast biomass can be used as an organic source for microbial biodiesel production. In this study, volatile fatty acids (VFAs), produced via anaerobic digestion of a lipid-extracted yeast (LEY) residue, were utilized as a carbon source for the yeast Cryptococcus curvatus. The response surface methodology was used to determine the initial pH and inoculum volume for the optimal VFA production. The experimental result for VFA concentration was 4.51 g/L at an initial pH of 9 and an inoculation 25%. The optimization results from the response surface methodology showed that the maximal VFA concentration was 4.58 g/L at an initial pH of 8.40 and an inoculation of 39.49%. This study indicates that VFAs from LEY can be used as a carbon source for microbial biodiesel production, with the potential to significantly reduce feedstock costs.
Gwon Woo Park; Seongsoo Son; Myounghoon Moon; Subin Sin; Kyoungseon Min; Jin-Suk Lee; Ho Nam Chang. Volatile Fatty Acids from Lipid-Extracted Yeast Provide Additional Feedstock for Microbial Lipid Production. Catalysts 2021, 11, 1009 .
AMA StyleGwon Woo Park, Seongsoo Son, Myounghoon Moon, Subin Sin, Kyoungseon Min, Jin-Suk Lee, Ho Nam Chang. Volatile Fatty Acids from Lipid-Extracted Yeast Provide Additional Feedstock for Microbial Lipid Production. Catalysts. 2021; 11 (8):1009.
Chicago/Turabian StyleGwon Woo Park; Seongsoo Son; Myounghoon Moon; Subin Sin; Kyoungseon Min; Jin-Suk Lee; Ho Nam Chang. 2021. "Volatile Fatty Acids from Lipid-Extracted Yeast Provide Additional Feedstock for Microbial Lipid Production." Catalysts 11, no. 8: 1009.
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.
The electrochemical conversion of CO2 can include renewable surplus electricity storage and CO2 utilisation. This review focuses on the microbial CO2 electrobiorefinery based on microbial electrosynthesis (MES) which merges electrochemical and microbial conversion to produce biofuels and higher-value chemicals. In this review, recent developments are discussed about bioelectrochemical conversion of CO2 into biofuels and chemicals in MES via microbial CO2-fixation and electricity utilisation reactions. In addition, this review examines technical approaches to overcome the current limitations of MES including the following: engineering of the biocathode, application of electron mediators, and reactor optimisation, among others. An in-depth discussion of strategies for the CO2 electrobiorefinery is presented, including the integration of the biocathode with inorganic catalysts, screening of novel electroactive microorganisms, and metabolic engineering to improve target productivity from CO2.
Soo Youn Lee; You-Kwan Oh; Sangmin Lee; Hana Nur Fitriana; Myounghoon Moon; Min-Sik Kim; Jiye Lee; Kyoungseon Min; Gwon Woo Park; Joon-Pyo Lee; Jin-Suk Lee. Recent developments and key barriers to microbial CO2 electrobiorefinery. Bioresource Technology 2020, 320, 124350 .
AMA StyleSoo Youn Lee, You-Kwan Oh, Sangmin Lee, Hana Nur Fitriana, Myounghoon Moon, Min-Sik Kim, Jiye Lee, Kyoungseon Min, Gwon Woo Park, Joon-Pyo Lee, Jin-Suk Lee. Recent developments and key barriers to microbial CO2 electrobiorefinery. Bioresource Technology. 2020; 320 ():124350.
Chicago/Turabian StyleSoo Youn Lee; You-Kwan Oh; Sangmin Lee; Hana Nur Fitriana; Myounghoon Moon; Min-Sik Kim; Jiye Lee; Kyoungseon Min; Gwon Woo Park; Joon-Pyo Lee; Jin-Suk Lee. 2020. "Recent developments and key barriers to microbial CO2 electrobiorefinery." Bioresource Technology 320, no. : 124350.
Formate dehydrogenase (FDH) has been considered as a nearly irreversible biocatalyst for catalyzing formate oxidation to CO2 for a long time. However, recent research clearly proved that certain FDHs, mainly NAD+-linked/metal (either W- or Mo-) containing enzymes, are capable of reversibly interconverting CO2 and formate, thereby having a significant role as a non-photosynthetic CO2 utilizing enzyme. We, herein, summarize and discuss not only recently discovered CO2 reduction activities and structure-based enzyme engineering reinforcing the CO2 reduction activity but also applications for a CO2 refinery including electroenzymatic approaches, whole-cell biocatalytic systems, and multi-enzyme cascade reactions in detail. Especially, this review concentrates on as well as comprehensively discusses recent progress. Furthermore, innovative results discussed herein might provide revelaratory insights applicable for constructing a feasible CO2 refinery system that utilizes CO2 as an abundant, cheap, and sustainable feedstock in order to produce value-added fuels and chemicals.
Myounghoon Moon; Gwon Woo Park; Joon-Pyo Lee; Jin-Suk Lee; Kyoungseon Min. Recent progress in formate dehydrogenase (FDH) as a non-photosynthetic CO2 utilizing enzyme: A short review. Journal of CO2 Utilization 2020, 42, 101353 .
AMA StyleMyounghoon Moon, Gwon Woo Park, Joon-Pyo Lee, Jin-Suk Lee, Kyoungseon Min. Recent progress in formate dehydrogenase (FDH) as a non-photosynthetic CO2 utilizing enzyme: A short review. Journal of CO2 Utilization. 2020; 42 ():101353.
Chicago/Turabian StyleMyounghoon Moon; Gwon Woo Park; Joon-Pyo Lee; Jin-Suk Lee; Kyoungseon Min. 2020. "Recent progress in formate dehydrogenase (FDH) as a non-photosynthetic CO2 utilizing enzyme: A short review." Journal of CO2 Utilization 42, no. : 101353.
Reutealis trisperma, due to its high kernel-oil yield (±50%) and long productivity (±70 years), is considered to be a promising feedstock for biodiesel production. In addition, this plant, which can thrive on marginal lands, is classified as a non-edible oil since it contains a toxin known as eleostearic acid. The present study aimed to optimize the esterification step in biodiesel production from R.trisperma oil catalyzed using sulfonic ion exchange resin Lewatit K2640. The optimization step was performed using a response surface methodology through the incorporation of a central composite design. A kinetic study was performed as well, based on the assumption of a pseudo-homogeneous second-order model. Catalyst loading was found to have the most significant impact on acid value, followed by temperature and methanol-to-oil molar ratio. The optimal conditions for the esterification step were 92 °C temperature, 5.34% catalyst loading, and 5.82:1 methanol-to-oil molar ratio. The acid value and FFA conversion of R.trisperma oil under these conditions were 2.49 mg KOH/g and 91.75%, respectively. The kinetics study revealed that the constructed model could fit the experimental data well with relatively high reliability. The activation energy required for the esterification of R.trisperma oil was 33.2 kJ/mol.
Riky Lim; Deog-Keun Kim; Jin-Suk Lee. Reutealis Trisperma Oil Esterification: Optimization and Kinetic Study. Energies 2020, 13, 1513 .
AMA StyleRiky Lim, Deog-Keun Kim, Jin-Suk Lee. Reutealis Trisperma Oil Esterification: Optimization and Kinetic Study. Energies. 2020; 13 (6):1513.
Chicago/Turabian StyleRiky Lim; Deog-Keun Kim; Jin-Suk Lee. 2020. "Reutealis Trisperma Oil Esterification: Optimization and Kinetic Study." Energies 13, no. 6: 1513.
Due to climate change, recent research interests have increased towards CO2 utilization as a strategy to mitigate the atmospheric CO2 level. Herein, we aimed to explore formate dehydrogenases (FDHs) from chemoautotroph to discover an efficient and O2-tolerant biocatalyst for catalyzing the CO2 reduction to a versatile formate. Through genome-mining and phylogenetic analysis, the FDH from Rhodobacter aestuarii (RaFDH) was newly discovered as a promising O2-tolernat CO2 reductase and was successfully expressed in Escherichia coli. In this study, the optimum conditions and turnover rates of RaFDH were examined for CO2 reduction and formate oxidation. In particular, the RaFDH-driven CO2 reduction far surpassed the formate oxidation with a turnover rate of 48.3 and 15.6 min−1, respectively. The outstanding superiority of RaFDH towards CO2 reduction can be applicable for constructing a feasible electroenzymatic system that produce a versatile formate from CO2 as a cheap, abundant, and renewable resource.
Kyoungseon Min; Yong-Soo Park; Gwon Woo Park; Joon-Pyo Lee; Myounghoon Moon; Chang Hyun Ko; Jin-Suk Lee. Elevated conversion of CO2 to versatile formate by a newly discovered formate dehydrogenase from Rhodobacter aestuarii. Bioresource Technology 2020, 305, 123155 .
AMA StyleKyoungseon Min, Yong-Soo Park, Gwon Woo Park, Joon-Pyo Lee, Myounghoon Moon, Chang Hyun Ko, Jin-Suk Lee. Elevated conversion of CO2 to versatile formate by a newly discovered formate dehydrogenase from Rhodobacter aestuarii. Bioresource Technology. 2020; 305 ():123155.
Chicago/Turabian StyleKyoungseon Min; Yong-Soo Park; Gwon Woo Park; Joon-Pyo Lee; Myounghoon Moon; Chang Hyun Ko; Jin-Suk Lee. 2020. "Elevated conversion of CO2 to versatile formate by a newly discovered formate dehydrogenase from Rhodobacter aestuarii." Bioresource Technology 305, no. : 123155.
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.
Tyrosinase (E.C. 1.14.18. 1) is a type of Cu-containing oxidoreductase which has bifunctional activity for various phenolic substrates: ortho-hydroxylation of monophenols to diphenols (a cresolase activity) and oxidation of diphenols to quinones (a catecholase activity). Based on the broad substrate spectrum, tyrosinase has been used in bioremediation of phenolic pollutants, constructing biosensors for identifying phenolic compounds, and L-DOPA synthesis. Furthermore, not only tyrosinase has been used to produce useful polyphenol derivatives, but also it is recently revealed that the promiscuous activity of tyrosinase is closely related with delignification in the biorefinery. Accordingly, tyrosinase might be a potential biocatalyst for industrial applications (e.g., electroenzymatic L-DOPA production, but its long-term stability and reusability should be further explored. In this review, we emphasize the versatility of tyrosinase, which includes conventional applications, and suggest new perspectives as an industrial biocatalyst (e.g., electroenzymatic L-DOPA production). Especially, this review focuses on and comprehensively discusses recent innovative studies.
Kyoungseon Min; Gwon Woo Park; Young Je Yoo; Jin-Suk Lee. A perspective on the biotechnological applications of the versatile tyrosinase. Bioresource Technology 2019, 289, 121730 .
AMA StyleKyoungseon Min, Gwon Woo Park, Young Je Yoo, Jin-Suk Lee. A perspective on the biotechnological applications of the versatile tyrosinase. Bioresource Technology. 2019; 289 ():121730.
Chicago/Turabian StyleKyoungseon Min; Gwon Woo Park; Young Je Yoo; Jin-Suk Lee. 2019. "A perspective on the biotechnological applications of the versatile tyrosinase." Bioresource Technology 289, no. : 121730.
Energy-saving, high-efficiency cell disruption is a critical step for recovery of thermolabile antioxidant astaxanthin from Haematococcus pluvialis cyst cells of rigid cell-wall structure. In this study, as room-temperature green solvents, 10 types of 1-ethyl-3-methylimidazolium ([Emim])-based ionic liquids (ILs) were compared and evaluated for their abilities to disrupt H. pluvialis cyst cells for astaxanthin/lipid extraction. Among the 10 ILs tested, 3 [Emim]-based ILs with HSO4, CH3SO3, and (CF3SO2)2N anions were selected based on astaxanthin/lipid extraction performance and synthesis cost. When pretreated with IL/water mixtures, intact cyst cells were significantly torn, broken or shown to release cytoplasmic components, thereby facilitating subsequent separation of astaxanthin/lipid by hexane. However, excess IL pretreatments at high temperature/IL dosages and longer incubation times significantly deteriorated lipid and/or astaxanthin. Under optimized mild conditions (6.7% (v/v) IL in water solution, 30°C, 60 min), almost complete astaxanthin recoveries (>99%) along with moderate lipid extractions (∼82%) could be obtained.
Sun-A Choi; You-Kwan Oh; Jiye Lee; Sang Jun Sim; Min Eui Hong; Ji-Yeon Park; Min-Sik Kim; Seung Wook Kim; Jin-Suk Lee. High-efficiency cell disruption and astaxanthin recovery from Haematococcus pluvialis cyst cells using room-temperature imidazolium-based ionic liquid/water mixtures. Bioresource Technology 2018, 274, 120 -126.
AMA StyleSun-A Choi, You-Kwan Oh, Jiye Lee, Sang Jun Sim, Min Eui Hong, Ji-Yeon Park, Min-Sik Kim, Seung Wook Kim, Jin-Suk Lee. High-efficiency cell disruption and astaxanthin recovery from Haematococcus pluvialis cyst cells using room-temperature imidazolium-based ionic liquid/water mixtures. Bioresource Technology. 2018; 274 ():120-126.
Chicago/Turabian StyleSun-A Choi; You-Kwan Oh; Jiye Lee; Sang Jun Sim; Min Eui Hong; Ji-Yeon Park; Min-Sik Kim; Seung Wook Kim; Jin-Suk Lee. 2018. "High-efficiency cell disruption and astaxanthin recovery from Haematococcus pluvialis cyst cells using room-temperature imidazolium-based ionic liquid/water mixtures." Bioresource Technology 274, no. : 120-126.
The surface area and pore size distribution of Eucalyptus samples that were pretreated by different methods were determined by the Brunauer⁻Emmett⁻Teller (BET) technique. Three methods were applied to prepare cellulosic biomass samples for the BET measurements, air, freeze, and critical point drying (CPD). The air and freeze drying caused a severe collapse of the biomass pore structures, but the CPD effectively preserved the biomass morphology. The surface area of the CPD prepared Eucalyptus samples were determined to be 58⁻161 m²/g, whereas the air and freeze dried samples were 0.5⁻1.3 and 1.0⁻2.4 m²/g, respectively. The average pore diameter of the CPD prepared Eucalyptus samples were 61⁻70 Å. The CPD preserved the Eucalyptus sample morphology by replacing water with a non-polar solvent, CO₂ fluid, which prevented hydrogen bond reformation in the cellulose.
Kyu-Young Kang; Kyung-Ran Hwang; Ji-Yeon Park; Joon-Pyo Lee; Jun-Seok Kim; Jin-Suk Lee. Critical Point Drying: An Effective Drying Method for Direct Measurement of the Surface Area of a Pretreated Cellulosic Biomass. Polymers 2018, 10, 676 .
AMA StyleKyu-Young Kang, Kyung-Ran Hwang, Ji-Yeon Park, Joon-Pyo Lee, Jun-Seok Kim, Jin-Suk Lee. Critical Point Drying: An Effective Drying Method for Direct Measurement of the Surface Area of a Pretreated Cellulosic Biomass. Polymers. 2018; 10 (6):676.
Chicago/Turabian StyleKyu-Young Kang; Kyung-Ran Hwang; Ji-Yeon Park; Joon-Pyo Lee; Jun-Seok Kim; Jin-Suk Lee. 2018. "Critical Point Drying: An Effective Drying Method for Direct Measurement of the Surface Area of a Pretreated Cellulosic Biomass." Polymers 10, no. 6: 676.
Biofuels are regarded as one of the most viable options for reduction of CO2 emissions in the transport sector. However, conventional plant-based biofuels (e.g., biodiesel, bioethanol)’s share of total transportation-fuel consumption in 2016 was very low, about 4%, due to several major limitations including shortage of raw materials, low CO2 mitigation effect, blending wall, and poor cost competitiveness. Advanced biofuels such as drop-in, microalgal, and electro biofuels, especially from inedible biomass, are considered to be a promising solution to the problem of how to cope with the growing biofuel demand. In this paper, recent developments in oxy-free hydrocarbon conversion via catalytic deoxygenation reactions, the selection of and lipid-content enhancement of oleaginous microalgae, electrochemical biofuel conversion, and the diversification of valuable products from biomass and intermediates are reviewed. The challenges and prospects for future development of eco-friendly and economically advanced biofuel production processes also are outlined herein.
You-Kwan Oh; Kyung-Ran Hwang; Changman Kim; Jung Rae Kim; Jin-Suk Lee. Recent developments and key barriers to advanced biofuels: A short review. Bioresource Technology 2018, 257, 320 -333.
AMA StyleYou-Kwan Oh, Kyung-Ran Hwang, Changman Kim, Jung Rae Kim, Jin-Suk Lee. Recent developments and key barriers to advanced biofuels: A short review. Bioresource Technology. 2018; 257 ():320-333.
Chicago/Turabian StyleYou-Kwan Oh; Kyung-Ran Hwang; Changman Kim; Jung Rae Kim; Jin-Suk Lee. 2018. "Recent developments and key barriers to advanced biofuels: A short review." Bioresource Technology 257, no. : 320-333.
Surface area and pore size distribution of Eucalyptus samples pretreated by different methods were determined by the Brunauer-Emmett-Teller (BET) technique. Three methods were applied to prepare cellulosic biomass samples for BET measurements: air, freeze, and critical point drying (CPD). Air and freeze drying caused severe collapse of biomass pore structures, but CPD effectively preserved biomass morphology. Surface area of CPD prepared Eucalyptus samples was determined to be 58–161 m2/g, whereas air and freeze dried samples were 0.5–1.3 and 1.0–2.4 m2/g, respectively. Average pore diameter of CPD prepared Eucalyptus samples were 61–70Å. CPD preserved Eucalyptus sample morphology by replacing water with a non-polar solvent, CO2 fluid, which prevented hydrogen bond reformation in the cellulose.
Kyu-Young Kang; Kyung Ran Hwang; Ji-Yeon Park; Joon-Pyo Lee; Jun-Seok Kim; Jin-Suk Lee. Critical Point Drying: An Effective Tool for Direct Measurement of the Surface Area of Pretreated Cellulosic Biomass. 2018, 1 .
AMA StyleKyu-Young Kang, Kyung Ran Hwang, Ji-Yeon Park, Joon-Pyo Lee, Jun-Seok Kim, Jin-Suk Lee. Critical Point Drying: An Effective Tool for Direct Measurement of the Surface Area of Pretreated Cellulosic Biomass. . 2018; ():1.
Chicago/Turabian StyleKyu-Young Kang; Kyung Ran Hwang; Ji-Yeon Park; Joon-Pyo Lee; Jun-Seok Kim; Jin-Suk Lee. 2018. "Critical Point Drying: An Effective Tool for Direct Measurement of the Surface Area of Pretreated Cellulosic Biomass." , no. : 1.
Current single-stage delignification-pretreatment technologies to overcome lignocellulosic biomass recalcitrance are usually achieved at the expense of compromising the recovery of the polysaccharide components, particularly the hemicellulose fraction. One way to enhance overall sugar recovery is to tailor an efficient two-stage pretreatment that can pre-extract the more labile hemicellulose component before subjecting the cellulose-rich residual material to a second-stage delignification process. Previous work had shown that a mild steam pretreatment could recover >65% of the hemicellulose from poplar while limiting the acid-catalysed condensation of lignin. This potentially allowed for subsequent lignin extraction using various lignin solvents to produce a more accessible cellulosic substrate. A two-stage approach using steam and/or solvent pretreatment was assessed for its ability to separate hemicellulose and lignin from poplar wood chips while providing a cellulose-rich fraction that could be readily hydrolysed by cellulase enzymes. An initial steam-pretreatment stage was performed over a range of temperatures (160–200 °C) using an equivalent severity factor of 3.6. A higher steam temperature of 190 °C applied over a shorter residence time of 10 min effectively solubilized and recovered 75% of the hemicellulose while enhancing the ability of various solvents [deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone (soda/AQ) or a hydrotrope] to extract lignin in a second stage. When the second-stage treatments were compared, the mild DES treatment (lactic acid and betaine) at 130 °C, removed comparable amounts of lignin with higher selectivity than did the soda/AQ and organosolv pretreatments at 170 °C. However, the cellulose-rich substrates obtained after the second-stage organosolv and soda/AQ pretreatments showed the highest cellulose accessibility, as measured by the Simon’s staining technique. They were also the most susceptible to subsequent enzymatic hydrolysis. The second-stage pretreatments varied in their ability to solubilize and extract the lignin component of steam-pretreated poplar while enhancing the enzymatic hydrolysis of the resulting cellulose-rich residual fractions. Although DES extraction was more selective in extracting lignin from the steam-pretreated substrates, the organosolv and soda/AQ post treatments disrupted the cellulose structure to a greater extent while enhancing the ease of enzymatic hydrolysis. Effective hemicellulose removal via steam pretreatment followed by subsequent lignin extraction under acidic, alkaline or solvolytic conditions results in a highly accessible, more readily hydrolysed cellulose fraction.
Dong Tian; Richard P. Chandra; Jin-Suk Lee; Canhui Lu; Jack N. Saddler. A comparison of various lignin-extraction methods to enhance the accessibility and ease of enzymatic hydrolysis of the cellulosic component of steam-pretreated poplar. Biotechnology for Biofuels 2017, 10, 1 -10.
AMA StyleDong Tian, Richard P. Chandra, Jin-Suk Lee, Canhui Lu, Jack N. Saddler. A comparison of various lignin-extraction methods to enhance the accessibility and ease of enzymatic hydrolysis of the cellulosic component of steam-pretreated poplar. Biotechnology for Biofuels. 2017; 10 (1):1-10.
Chicago/Turabian StyleDong Tian; Richard P. Chandra; Jin-Suk Lee; Canhui Lu; Jack N. Saddler. 2017. "A comparison of various lignin-extraction methods to enhance the accessibility and ease of enzymatic hydrolysis of the cellulosic component of steam-pretreated poplar." Biotechnology for Biofuels 10, no. 1: 1-10.
In this study, lipid extraction from Chlorella vulgaris was performed by using mixtures of molten salt and ionic liquid. The yield-enhancing effects of blending of molten salt with ionic liquid were investigated. Among the three molten salts (Zn(NO3)2·6H2O, Mg(ClO4)2·6H2O, and FeCl3·6H2O), FeCl3·6H2O showed a high lipid extraction yield (113.0 mg/g cell) and good reaction performance. When FeCl3·6H2O was mixed with [Emim]OAc (5:1, w/w), the lipid extraction yield increased to 227.6 mg/g cell, a performance similar to that of single [Emim]OAc (218.7 mg/g cell). When lipid was extracted by the FeCl3·6H2O/[Emim]OAc mixture at a 5:1 (w/w) blending ratio, 90 °C temperature, and 1 h duration, the fatty acid content of the extracted lipid was 981.7 mg/g lipid, indicating less than 2% impurity. The lipid extraction from C. vulgaris was improved by the synergistic effects of molten salt and ionic liquid with different ions.
Sun-A Choi; Jin-Suk Lee; You-Kwan Oh; Min-Ji Jeong; Seung Wook Kim; Ji-Yeon Park. Lipid extraction from Chlorella vulgaris by molten-salt/ionic-liquid mixtures. Algal Research 2013, 3, 44 -48.
AMA StyleSun-A Choi, Jin-Suk Lee, You-Kwan Oh, Min-Ji Jeong, Seung Wook Kim, Ji-Yeon Park. Lipid extraction from Chlorella vulgaris by molten-salt/ionic-liquid mixtures. Algal Research. 2013; 3 ():44-48.
Chicago/Turabian StyleSun-A Choi; Jin-Suk Lee; You-Kwan Oh; Min-Ji Jeong; Seung Wook Kim; Ji-Yeon Park. 2013. "Lipid extraction from Chlorella vulgaris by molten-salt/ionic-liquid mixtures." Algal Research 3, no. : 44-48.
In this study, pre-biodiesel-production lipid extraction from microalgae (Chlorella vulgaris) was performed. The yield-enhancing effects of ionic liquid blends on the lipid extraction were investigated. The initial fatty acids content of the C. vulgaris was 292.2 mg/g cell. The lipid extraction yield using single ionic liquids was compared with the yield obtained with organic solvents and ionic liquid mixtures, respectively. The yield by hexane–methanol solvent was 185.4 mg/g cell. Among the 12 ionic liquids, 1-ethyl-3-methyl imidazolium acetate, 1-ethyl-3-methyl imidazolium diethylphosphate, 1-ethyl-3-methyl imidazolium tetrafluoroborate, and 1-ethyl-3-methyl imidazolium chloride showed high (>200.0 mg/g cell) lipid extraction yields. Although the yields of 1-ethyl-3-methyl imidazolium ethyl sulfate and 1-ethyl-3-methyl imidazolium thiocyanate were only 60.5 and 42.7 mg/g cell, respectively, the yield for their mixture (weight ratio of 1:1) was improved to 158.2 mg/g cell. Similarly, whereas the lipid extraction yield of 1-ethyl-3-methyl imidazolium hydrogen sulfate was just 35.2 mg/g cell, that for its mixture with 1-ethyl-3-methyl imidazolium thiocyanate (weight ratio of 1:1) was boosted to 200.6 mg/g cell. Overall, the synergistic effects of the ionic liquid mixtures with different anions improved the lipid extraction yield of C. vulgaris.
Sun-A Choi; You-Kwan Oh; Min-Ji Jeong; Seung Wook Kim; Jin-Suk Lee; Ji-Yeon Park. Effects of ionic liquid mixtures on lipid extraction from Chlorella vulgaris. Renewable Energy 2013, 65, 169 -174.
AMA StyleSun-A Choi, You-Kwan Oh, Min-Ji Jeong, Seung Wook Kim, Jin-Suk Lee, Ji-Yeon Park. Effects of ionic liquid mixtures on lipid extraction from Chlorella vulgaris. Renewable Energy. 2013; 65 ():169-174.
Chicago/Turabian StyleSun-A Choi; You-Kwan Oh; Min-Ji Jeong; Seung Wook Kim; Jin-Suk Lee; Ji-Yeon Park. 2013. "Effects of ionic liquid mixtures on lipid extraction from Chlorella vulgaris." Renewable Energy 65, no. : 169-174.
Empty fruit bunch (EFB) has many advantages, including its abundance, the fact that it does not require collection, and its year-round availability as a feedstock for bioethanol production. But before the significant costs incurred in ethanol production from lignocellulosic biomass can be reduced, an efficient sugar fractionation technology has to be developed. To that end, in the present study, an NaOH-catalyzed steam pretreatment process was applied in order to produce ethanol from EFB more efficiently. The EFB pretreatment conditions were optimized by application of certain pretreatment variables such as, the NaOH concentrations in the soaking step and, in the steam step, the temperature and time. The optimal conditions were determined by response surface methodology (RSM) to be 3% NaOH for soaking and 160°C, 11 min 20 sec for steam pretreatment. Under these conditions, the overall glucan recovery and enzymatic digestibility were both high: the glucan and xylan yields were 93% and 78%, respectively, and the enzymatic digestibility was 88.8% for 72 h using 40 FPU/g glucan. After simultaneous saccharification and fermentation (SSF), the maximum ethanol yield and concentration were 0.88 and 29.4 g/l respectively. Delignification (>85%) of EFB was an important factor in enzymatic hydrolysis using CTec2. NaOH-catalyzed steam pretreatment, which can remove lignin efficiently and requires only a short reaction time, was proven to be an effective pretreatment technology for EFB. The ethanol yield obtained by SSF, the key parameter determining the economics of ethanol, was 18% (w/w), equivalent to 88% of the theoretical maximum yield, which is a better result than have been reported in the relevant previous studies.
Won-Il Choi; Ji-Yeon Park; Joon-Pyo Lee; You-Kwan Oh; Yong Chul Park; Jun Seok Kim; Jang Min Park; Chul Ho Kim; Jin-Suk Lee. Optimization of NaOH-catalyzed steam pretreatment of empty fruit bunch. Biotechnology for Biofuels 2013, 6, 170 -170.
AMA StyleWon-Il Choi, Ji-Yeon Park, Joon-Pyo Lee, You-Kwan Oh, Yong Chul Park, Jun Seok Kim, Jang Min Park, Chul Ho Kim, Jin-Suk Lee. Optimization of NaOH-catalyzed steam pretreatment of empty fruit bunch. Biotechnology for Biofuels. 2013; 6 (1):170-170.
Chicago/Turabian StyleWon-Il Choi; Ji-Yeon Park; Joon-Pyo Lee; You-Kwan Oh; Yong Chul Park; Jun Seok Kim; Jang Min Park; Chul Ho Kim; Jin-Suk Lee. 2013. "Optimization of NaOH-catalyzed steam pretreatment of empty fruit bunch." Biotechnology for Biofuels 6, no. 1: 170-170.
Intensive studies are underway to develop more efficient biodiesel conversion processes. Among the various new technologies, both solid catalyst and non-catalytic supercritical processes are recognized as those that can be turned to practical use in the near future. The current status and challenging issues for these two technologies are, therefore, reviewed in this work as innovative biodiesel production technologies.
Jin-Suk Lee; Shiro Saka. Biodiesel production by heterogeneous catalysts and supercritical technologies. Bioresource Technology 2010, 101, 7191 -7200.
AMA StyleJin-Suk Lee, Shiro Saka. Biodiesel production by heterogeneous catalysts and supercritical technologies. Bioresource Technology. 2010; 101 (19):7191-7200.
Chicago/Turabian StyleJin-Suk Lee; Shiro Saka. 2010. "Biodiesel production by heterogeneous catalysts and supercritical technologies." Bioresource Technology 101, no. 19: 7191-7200.
To maximize the production of biodiesel from soybean soapstock, the effects of water on the esterification of high-FFA (free fatty acid) oils were investigated. Oleic acid and high acid acid oil (HAAO) were esterified by reaction with methanol in the presence of Amberlyst-15 as a heterogeneous catalyst or sulfuric acid as a homogeneous catalyst. The yield of fatty acid methyl ester (FAME) was studied at oil to methanol molar ratios of 1:3 and 1:6 and reaction temperatures of 60 and 80 °C. The rate of esterification of oleic acid significantly decreased as the initial water content increased to 20% of the oil. The activity of Amberlyst-15 decreased more rapidly than that of sulfuric acid, due to the direct poisoning of acid sites by water. Esterification using sulfuric acid was not affected by water until there was a 5% water addition at a 1:6 molar ratio of oil to methanol. FAME content of HAAO prepared from soapstock rapidly increased for the first 30 min of esterification. Following the 30-min mark, the rate of FAME production decreased significantly due to the accumulation of water. When methanol and Amberlyst-15 were removed from the HAAO after 30 min of esterification and fresh methanol and a catalyst were added, the time required to reach 85% FAME content was reduced from 6 h to 1.8 h.
Ji-Yeon Park; Zhong-Ming Wang; Deog-Keun Kim; Jin-Suk Lee. Effects of water on the esterification of free fatty acids by acid catalysts. Renewable Energy 2010, 35, 614 -618.
AMA StyleJi-Yeon Park, Zhong-Ming Wang, Deog-Keun Kim, Jin-Suk Lee. Effects of water on the esterification of free fatty acids by acid catalysts. Renewable Energy. 2010; 35 (3):614-618.
Chicago/Turabian StyleJi-Yeon Park; Zhong-Ming Wang; Deog-Keun Kim; Jin-Suk Lee. 2010. "Effects of water on the esterification of free fatty acids by acid catalysts." Renewable Energy 35, no. 3: 614-618.