Yuseong gu, South Korea
Yuseong gu, South Korea

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Park S.,Petroleum RM Team | Kim K.,91 Daehak ro | Han S.-I.,Korea University | Kim E.J.,Mokpo National University | Choi Y.-E.,Korea University
Applied Biological Chemistry | Year: 2017

Increasing demand for renewable energy has led to the production of biodiesel from microalgae. Microalgae have been regarded as one of the best feedstocks for biodiesel due to their high growth rate and lipid content as compared to other crops and plants. However, use of microalgae is still hindered by technical barriers and high processing costs. The economic viability and environmentally friendly aspects of biodiesel production will be significantly improved by co-producing value-added chemicals and extracting lipids directly from wet biomass without involvement of organic solvents, respectively. In this study, organic solvent-free lipid extraction from wet Aurantiochytrium sp. biomass was developed to co-produce biodiesel and value-added products such as docosahexaenoic acid. Organic solvent-free lipid extraction was performed by applying alkali and heat treatments to wet biomass. Key parameters for the extraction from Aurantiochytrium sp. were optimized to increase extraction yields. A ratio of 15 mg/mL of biomass to alkaline solution and an alkaline solution concentration of 1% w/w were determined to be the optimal conditions. Both heating temperature and treatment time were associated with positive effects on lipid recovery, up to a certain level. The maximum extraction yield (77.37% of total lipid) was obtained by heating at 150 °C for 30 min. Additionally, microwaves were employed to the extraction system and could further reduce the reaction time. Our study could be expanded to other types of microalgal biomass and will aid in establishing a protocol for organic solvent-free lipid extraction directly from wet biomass. © 2017 The Korean Society for Applied Biological Chemistry


Park T.J.,Chung - Ang University | Heo N.S.,BioProcess Engineering Research Center | Yim S.S.,91 Daehak ro | Park J.H.,91 Daehak ro | And 3 more authors.
Microbial Cell Factories | Year: 2013

Background: The anchoring motif is one of the most important aspects of cell surface display as well as efficient and stable display of target proteins. Thus, there is currently a need for the identification and isolation of novel anchoring motifs.Results: A system for the display of recombinant proteins on the surface of Escherichia coli was developed using the Bacillus anthracis exosporal protein (BclA) as a new anchoring motif. For the surface display of recombinant proteins, the BAN display platform was constructed in which a target protein is linked to the C-terminus of N-terminal domain (21 amino acids) of BclA. The potential application of BAN platform for cell surface display was demonstrated with two model proteins of different size, the Bacillus sp. endoxylanase (XynA) and monooxygenase (P450 BM3m2). Through experimental analysis including outer membrane fractionation, confocal microscopy and activity assay, it was clearly confirmed that both model proteins were successfully displayed with high activities on the E. coli cell surface.Conclusions: These results of this study suggest that the strategy employing the B. anthracis BclA as an anchoring motif is suitable for the display of heterologous proteins on the surface of E. coli and consequently for various biocatalytic applications as well as protein engineering. © 2013 Park et al.; licensee BioMed Central Ltd.


Yun Y.-M.,91 Daehak ro | Shin H.-S.,91 Daehak ro | Lee C.-K.,Korea Institute of Civil Engineering and Building Technology | Oh Y.-K.,Korea Institute of Energy Research | Kim H.-W.,Chonbuk National University
Environmental Science and Pollution Research | Year: 2015

Converting lipid-extracted microalgal wastes to methane (CH4) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining n-hexane (C6H14) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual n-hexane, this study conducted a series of batch AD by mixing lipid-extracted Chlorella vulgaris with a wide range of n-hexane concentration (∼10 g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of n-hexane on CH4 yield was negligible up to 2 g COD/L and inhibition to methanogenesis became significant when it was higher than 4 g COD/L based on quantitative mass balance. Inhibition threshold was about 4 g COD/L of n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as n-hexane concentration increased. These findings offer a useful guideline of threshold n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes. © 2015 Springer-Verlag Berlin Heidelberg


Noh S.M.,91 Daehak ro | Park J.H.,91 Daehak ro | Lim M.S.,New Drug Development Center | Kim J.W.,New Drug Development Center | Lee G.M.,91 Daehak ro
Applied Microbiology and Biotechnology | Year: 2016

Chinese hamster ovary (CHO) cell cultivation for production of therapeutic proteins is accompanied by production of metabolic wastes, mostly ammonia and lactate. To reduce ammonia production, the glutamine synthetase (GS) system was used to develop therapeutic monoclonal antibody (mAb)-producing CHO cells (SM-0.025). Additionally, the lactate dehydrogenase-A (LDH-A) was downregulated with shRNA to reduce lactate production in SM-0.025. The resulting mAb-producing cell lines (#2, #46, and #52) produced less ammonia than the host cell line during the exponential phase due to GS protein overexpression. LDH-A downregulation in SM-0.025 not only reduced lactate production but also further reduced ammonia production. Among the three LDH-A-downregulated clones, clone #2 had the highest mAb production along with significantly reduced specific lactate and ammonia production rates compared to those in SM-0.025. Waste reduction increased the galactosylation level of N-glycosylation, which improved mAb quality. LDH-A downregulation was also successfully applied to the host cell lines (CHO K1 and GS knockout CHO-K1). However, LDH-A downregulated host cells could not survive the pool-selection process wherein glutamine was excluded and methionine sulfoximine was added to the media. Taken together, LDH-A downregulation in the mAb-producing cell line generated with the GS system successfully reduced both ammonia and lactate levels, improving mAb galactosylation. However, LDH-A downregulation could not be applied to host cell lines because it hampered the selection process of the GS system. © 2016 Springer-Verlag Berlin Heidelberg


Adler I.,University of Leeds | Kante M.M.,University Blaise Pascal | Kwon O.-J.,91 Daehak ro | Kwon O.-J.,Hungarian Academy of Sciences
Algorithmica | Year: 2016

Linear rank-width is a linearized variation of rank-width, and it is deeply related to matroid path-width. In this paper, we show that the linear rank-width of every n-vertex distance-hereditary graph, equivalently a graph of rank-width at most 1, can be computed in time (Formula presented.), and a linear layout witnessing the linear rank-width can be computed with the same time complexity. As a corollary, we show that the path-width of every n-element matroid of branch-width at most 2 can be computed in time (Formula presented.), provided that the matroid is given by its binary representation. To establish this result, we present a characterization of the linear rank-width of distance-hereditary graphs in terms of their canonical split decompositions. This characterization is similar to the known characterization of the path-width of forests given by Ellis, Sudborough, and Turner [The vertex separation and search number of a graph. Inf. Comput., 113(1):50–79, 1994]. However, different from forests, it is non-trivial to relate substructures of the canonical split decomposition of a graph with some substructures of the given graph. We introduce a notion of ‘limbs’ of canonical split decompositions, which correspond to certain vertex-minors of the original graph, for the right characterization. © 2016 Springer Science+Business Media New York


To verify the interconnective relationship between biodegradation efficiency and microfibril structure, recalcitrant rice straw (RS) was depolymerized using water soaking-based microbiological biodegradation (WSMB). This eco-friendly biosystem, which does not predominantly generate inhibitory metabolites, could increase both the hydrolytic accessibility and fermentation efficiency of RS. In detail, when swollen RS (with Fenton cascades) was simultaneously bio-treated with Phanerochaete chrysosporium for 12 days, the biodegradability was 65.0 % of the theoretical maximum at the stationary phase. This value was significantly higher than the 30.3 % measured from untreated RS. Similarly, the WSMB platform had an effect on the yield enhancement of ethanol productivity of 32.5 %. However, uniform exposure of fibril polymers appeared to have little impact on bioconversion yields. Additionally, the proteomic pools of the WSMB system were analyzed to understand either substrate-specific or nonspecific biocascades based on the change in microcomposite materials. Remarkably, regardless of modified microfibril chains, the significant pattern of 14 major proteins (|fold| > 2) was reasonably analogous in both systems, especially for lignocellulolysis-related targets. © 2015 Springer Science+Business Media New York


Yoo B.,91 Daehak ro | Kim J.,91 Daehak ro
Journal of Marine Science and Technology (Japan) | Year: 2015

This study proposes a path planning algorithm for marine vehicles based on machine learning. The algorithm considers the dynamic characteristics of the vehicle and disturbance effects in ocean environments. The movements of marine vehicles are influenced by various physical disturbances in ocean environments, such as wind, waves, and currents. In the present study, the effects of ocean currents are the primary consideration. A kinematic model is used to incorporate the nonholonomic motion characteristics of a marine vehicle, and the reinforcement learning algorithm is used for path optimization to generate a feasible path that can be tracked by the vehicle. The proposed approach determines a near-optimal path that connects the start and goal points with a reasonable computational cost when the map and current field data are provided. To verify the optimality and validity of the proposed algorithm, a set of simulations were performed in simulated and actual ocean current conditions, and their results are presented. © 2015 JASNAOE


Kim T.,91 Daehak ro | Kim J.,91 Daehak ro | Choi H.-T.,Korea Research Institute of Ships and Ocean Engineering
Intelligent Service Robotics | Year: 2016

Mobile robots are generally equipped with proprioceptive motion sensors such as odometers and inertial sensors. These sensors are used for dead-reckoning navigation in an indoor environment where GPS is not available. However, this dead-reckoning scheme is susceptible to drift error in position and heading. This study proposes using grid line patterns which are often found on the surface of floors or ceilings in an indoor environment to obtain pose (i.e., position and orientation) fix information without additional external position information by artificial beacons or landmarks. The grid lines can provide relative pose information of a robot with respect to the grid structure and thus can be used to correct the pose estimation errors. However, grid line patterns are repetitive in nature, which leads to difficulties in estimating its configuration and structure using conventional Gaussian filtering that represent the system uncertainty using a unimodal function (e.g., Kalman filter). In this study, a probabilistic sensor model to deal with multiple hypotheses is employed and an online navigation filter is designed in the framework of particle filtering. To demonstrate the performance of the proposed approach, an experiment was performed in an indoor environment using a wheeled mobile robot, and the results are presented. © 2016 Springer-Verlag Berlin Heidelberg


Lee S.-Y.,91 Daehak ro | Jung E.-S.,91 Daehak ro
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We propose to use EEG signals to make user authentication for requiring high security. EEG signals were measured while the subjects saw several images in sequences. Since subjectsa EEG signals are different for known and unknown images, these EEG sequences may be used to identify each subject. Correlation analysis and classification results show the feasibility of user authentication from EEG signals. ©2014 SPIE.


Kang H.,91 Daehak ro | Ahn Y.-H.,91 Daehak ro | Koh D.-Y.,91 Daehak ro | Lee H.,91 Daehak ro
Korean Journal of Chemical Engineering | Year: 2016

-It has been reported that some aldehyde compounds have formed simple sII clathrate hydrates without help-gas molecules, showing a self-forming effect. However, the structure of aldehyde hydrates is quite unstable due to the “gem-diol reaction”. According to the previous studies, the aldehyde hydrate slowly decomposes at atmospheric condition with the conversion of aldehyde to gem-diol. We investigated binary aldehyde (acetaldehyde, propionaldehyde, and isobutyraldehyde)+methane clathrate hydrate with spectroscopic and thermodynamic analyses. Similar to the simple aldehyde hydrate, the binary hydrates also formed a sII hydrate. During the hydrate formation process, we found that most of the aldehydes converted to gem-diols and were then incorporated into the large cages of the sII hydrate. Depending on the equilibrium constant of the gem-diol reaction caused by the molecular structures of the three aldehydes, different phase equilibrium curves of aldehyde+methane hydrates were obtained. © 2016 Korean Institute of Chemical Engineers, Seoul, Korea

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