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result(s) for
"Kim, Daehwan"
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Physico-Chemical Conversion of Lignocellulose: Inhibitor Effects and Detoxification Strategies: A Mini Review
2018
A pretreatment of lignocellulosic biomass to produce biofuels, polymers, and other chemicals plays a vital role in the biochemical conversion process toward disrupting the closely associated structures of the cellulose-hemicellulose-lignin molecules. Various pretreatment steps alter the chemical/physical structure of lignocellulosic materials by solubilizing hemicellulose and/or lignin, decreasing the particle sizes of substrate and the crystalline portions of cellulose, and increasing the surface area of biomass. These modifications enhance the hydrolysis of cellulose by increasing accessibilities of acids or enzymes onto the surface of cellulose. However, lignocellulose-derived byproducts, which can inhibit and/or deactivate enzyme and microbial biocatalysts, are formed, including furan derivatives, lignin-derived phenolics, and carboxylic acids. These generation of compounds during pretreatment with inhibitory effects can lead to negative effects on subsequent steps in sugar flat-form processes. A number of physico-chemical pretreatment methods such as steam explosion, ammonia fiber explosion (AFEX), and liquid hot water (LHW) have been suggested and developed for minimizing formation of inhibitory compounds and alleviating their effects on ethanol production processes. This work reviews the physico-chemical pretreatment methods used for various biomass sources, formation of lignocellulose-derived inhibitors, and their contributions to enzymatic hydrolysis and microbial activities. Furthermore, we provide an overview of the current strategies to alleviate inhibitory compounds present in the hydrolysates or slurries.
Journal Article
Bacillus Cellulase Molecular Cloning, Expression, and Surface Display on the Outer Membrane of Escherichia coli
by
Kim, Daehwan
,
Ku, Seockmo
in
Bacillus - enzymology
,
Bacillus - genetics
,
Bacillus licheniformis
2018
One of the main challenges of using recombinant enzymes is that they are derived from genetically-modified microorganisms commonly located in the intracellular region. The use of these recombinant enzymes for commercial purposes requires the additional processes of cell disruption and purification, which may result in enzyme loss, denaturation, and increased total production cost. In this study, the cellulase gene of Bacillus licheniformis ATCC 14580 was cloned, over-expressed, and surface displayed in recombinant Escherichia coli using an ice-nucleation protein (INP). INP, an outer membrane-bound protein from Pseudomonas syringae, was utilized as an anchor linker, which was cloned with a foreign cellulase gene into the pET21a vector to develop a surface display system on the outer membrane of E. coli. The resulting strain successfully revealed cellulase on the host cell surface. The over-expressed INP-cellulase fusion protein was confirmed via staining assay for determining the extracellular cellulase and Western blotting method for the molecular weight (MW) of cellulase, which was estimated to be around 61.7 kDa. Cell fractionation and localization tests demonstrated that the INP-cellulase fusion protein was mostly present in the supernatant (47.5%) and outer membrane (19.4%), while the wild-type strain intracellularly retained enzymes within cytosol (>61%), indicating that the INP gene directed the cellulase expression on the bacteria cell surface. Further studies of the optimal enzyme activity were observed at 60 °C and pH 7.0, and at least 75% of maximal enzyme activity was preserved at 70 °C.
Journal Article
Improvement of a Green’s Function Estimation for a Moving Source Using the Waveguide Invariant Theory
2024
Understanding the characteristics of underwater sound channels is essential for various remote sensing applications. Typically, the time-domain Green’s function or channel impulse response (CIR) is obtained using computationally intensive acoustic propagation models that rely on accurate environmental data, such as sound speed profiles and bathymetry. Ray-based blind deconvolution (RBD) offers a less computationally demanding alternative using plane-wave beamforming to estimate the Green’s function. However, the presence of noise can obscure low coherence ray arrivals, making accurate estimation challenging. This paper introduces a method using the waveguide invariant to improve the signal-to-noise ratio (SNR) of broadband Green’s functions for a moving source without prior knowledge of range. By utilizing RBD and the frequency shifts from the striation slope, we coherently combine individual Green’s functions at adjacent ranges, significantly improving the SNR. In this study, we demonstrated the proposed method via simulation and broadband noise data (200–900 Hz) collected from a moving ship in 100 m deep shallow water.
Journal Article
β-aminoisobutyric acid attenuates LPS-induced inflammation and insulin resistance in adipocytes through AMPK-mediated pathway
by
Park, Hyung Sub
,
Lee, Taeseung
,
Jung, Tae Woo
in
3T3-L1 Cells
,
Adipocyte
,
Adipocytes - drug effects
2018
Background
β-aminoisobutyric acid (BAIBA) is produced in skeletal muscle during exercise and has beneficial effects on obesity-related metabolic disorders such as diabetes and non-alcoholic fatty liver disease. Thus, it is supposed to prevent high fat diet (HFD)-induced inflammation and insulin resistance in adipose tissue though anti-inflammatory effects in obesity. Previous reports have also demonstrated strong anti-inflammatory effects of BAIBA.
Methods
We used BAIBA treated fully differentiated 3T3T-L1 mouse adipocytes to investigate the effects of exogenous BAIBA on inflammation and insulin signaling in adipocytes. Insulin signaling-mediated proteins and inflammation markers were measured by Western blot analysis. Secretion of pro-inflammatory cytokines were measured by ELISA. Lipid accumulation in differentiated 3 T3-L1 cells was stained by Oil red-O. Statistical analysis was performed by ANOVA and student’s
t
test.
Results
BAIBA treatment suppressed adipogenesis assessed by adipogenic markers as well as lipid accumulation after full differentiation. We showed that BAIBA treatment stimulated AMP-activated protein kinase (AMPK) phosphorylation in a dose-dependent manner and lipopolysaccharide (LPS)-induced secretion of pro-inflammatory cytokines such as TNFα and MCP-1 was abrogated in BAIBA-treated 3 T3-L1 cells. Treatment of 3 T3-L1 cells with BAIBA reduced LPS-induced NFκB and IκB phosphorylation. Furthermore, BAIBA treatment ameliorated LPS-induced impairment of insulin signaling measured by IRS-1 and Akt phosphorylation and fatty acid oxidation. Suppression of AMPK by small interfering (si) RNA significantly restored these changes.
Conclusions
We demonstrated anti-inflammatory and anti-insulin resistance effects of BAIBA in differentiated 3 T3-L1 cells treated with LPS through AMPK-dependent signaling. These results provide evidence for the beneficial effects of BAIBA not only in liver and skeletal muscle cells but also in adipose tissue.
Journal Article
Exploring the Psychological Mechanism of How the Multidimensional Service Quality of Fitness Centers Affects Consumer Satisfaction and Loyalty Depending on the Level of Exercise Involvement
2024
This study aimed to examine the influence of core services and the physical servicescape and social servicescape on consumer satisfaction and loyalty via perceived price fairness, flow experience, and rapport in fitness centers. Additionally, the present study explored how exercise involvement moderates the relationship between perceived price fairness, flow experience, rapport, and consumer satisfaction. For these purposes, targeting adults using fitness centers in South Korea, a total of 763 participants were sampled based on a cross-sectional design and used for data analyses involving confirmatory factor analysis for measurement validation and latent moderated structural equation modeling for hypothesis testing. The results showed that the core services, physical servicescape, and social servicescape enhance perceived price fairness, flow experiences, and rapport between staff and consumers, respectively. The study findings also indicated that exercise involvement significantly moderates the effect of price fairness and flow experience on satisfaction but not rapport. These insights offer practical and theoretical implications for fitness center management, emphasizing the importance of tailored service strategies in retaining loyal customers.
Journal Article
The Impact of Animated Mascot Displays on Consumer Evaluations in E-Commerce
2025
This study investigates consumer reactions to mascots on e-commerce websites, focusing on how anthropomorphic visual cues influence website satisfaction, revisit intention, and purchase intention. Specifically, we examine how mascot movement affects consumers’ sense of social presence and engagement, as well as the role of team identification in these effects. A 3 (mascot type: none, static, animated) × 2 (team identification: high, low) between-subjects experiment was conducted with 203 participants recruited from Amazon Mechanical Turk. Our findings show that the presence of mascots significantly impacts consumer evaluations, with social presence and engagement acting as sequential mediators. Notably, high team identification moderates the effect of animated mascots on revisit and purchase intentions but does not affect website satisfaction. These results provide valuable theoretical and practical insights for marketing, highlighting the importance of mascot design and movement in enhancing e-commerce experiences.
Journal Article
The Effect of Esports Content Attributes on Viewing Flow and Well-Being: A Focus on the Moderating Effect of Esports Involvement
2023
Despite being recognized as a global entertainment phenomenon, the nature of esports has been a subject of ongoing debate due to its content attributes and the controversial impact it has on individuals’ physical and mental well-being. We contend that the fundamental source of contention lies within the inherent content attributes of esports. Drawing on uses and gratification theory (UG) and cognitive appraisal theory, the purpose of the current study was to explore how esports content attributes and viewers’ individual characteristics (esports involvement) influence the viewer’s experience (flow experience) and well-being (happiness and vitality). The results of a latent moderated structural equations (LMS) modeling analysis using a total of 539 viewers revealed that entertainment, reliability, and diversity significantly influenced flow experience, which in turn influenced viewers’ happiness and vitality. Esports involvement was found to have moderating effects on the relationship between reliability and usefulness attributes and flow experience. The findings of this research provide important contributions to the literature and have implications for sport marketing managers.
Journal Article
A Rho Kinase (ROCK) Inhibitor, Y-27632, Inhibits the Dissociation-Induced Cell Death of Salivary Gland Stem Cells
2021
Salivary gland stem cells (SGSCs) are potential cell sources for the treatment of salivary gland diseases. The control of cell survival is an essential factor for applying stem cells to regenerative medicine or stem cell-based research. The purpose of this study was to investigate the effects of the ROCK inhibitor Y-27632 on the survival of SGSCs and its underlying mechanisms. SGSCs were isolated from mouse submandibular glands and cultured in suspension. Treatment with Y-27632 restored the viability of SGSCs that was significantly decreased during isolation and the subsequent culture. Y-27632 upregulated the expression of anti-apoptotic protein BCL-2 in SGSCs and, in the apoptosis assay, significantly reduced apoptotic and necrotic cell populations. Matrigel was used to mimic the extracellular environment of an intact salivary gland. The expression of genes regulating apoptosis and the ROCK signaling pathway was significantly reduced when SGSCs were embedded in Matrigel. SGSCs cultured in Matrigel and treated with Y-27632 showed no difference in the total numbers of spheroids and expression levels of apoptosis-regulating genes. Matrigel-embedded SGSCs treated with Y-27632 increased the number of spheroids with budding structures and the expression of acinar cell-specific marker AQP5. We demonstrate the protective effects of Y-27632 against dissociation-induced apoptosis of SGSCs during their culture in vitro.
Journal Article
Health risk assessment and source tracking of heavy metal exposure from indoor settled dust in an environmentally vulnerable area of the Republic of Korea
by
Sung, Kyunghwa
,
Min, Gihong
,
Shin, Jihun
in
692/499
,
704/172
,
Air Pollution, Indoor - analysis
2025
Accelerated urban and industrial expansion has intensified anthropogenic activities, increasing the emission and accumulation of hazardous substances in air, water, and soil. This study assessed health risks from heavy metals in indoor settled dust collected from Myodo-dong, Yeosu, Republic of Korea, by estimating exposure via inhalation, dermal contact, and ingestion, deriving protective exposure limits, and identifying emission sources using multivariate analysis. Indoor settled dust samples from 20 of 50 households showed elevated heavy metal concentrations, with zinc (Zn) having the highest mean level (4,912.01 µg/g). Ingestion was the dominant exposure route. Non-carcinogenic risks were within acceptable limits, while carcinogenic risks surpassed 1.0 × 10
− 6
for cadmium (Cd) and nickel (Ni). Cd risk was mainly ingestion-driven, whereas Ni posed the greatest concern through ingestion and dermal exposure. Lead (Pb) showed consistently low risk. Source identifications were analyzed using Pearson correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA), which grouped metals into three clusters, suggesting shared industrial origins. Positive matrix factorization (PMF) resolved five sources, four of which matched industrial sectors in pollutant release and transfer register (PRTR) data, including battery manufacturing, plastics, non-ferrous metal processing, and ceramics. Source 1, dominated by Cd, was not identified due to inventory gaps, but fenceline regression showed a strong correlation (R
2
= 0.983,
p
< 0.01) between Cd in ambient air and indoor settled dust, implicating emissions from a nearby steel facility.
Journal Article
Optimization and Scale-Up of Coffee Mucilage Fermentation for Ethanol Production
2018
Coffee, one of the most popular food commodities and beverage ingredients worldwide, is considered as a potential source for food industry and second-generation biofuel due to its various by-products, including mucilage, husk, skin (pericarp), parchment, silver-skin, and pulp, which can be produced during the manufacturing process. A number of research studies have mainly investigated the valuable properties of brewed coffee (namely, beverage), functionalities, and its beneficial effects on cognitive and physical performances; however, other residual by-products of coffee, such as its mucilage, have rarely been studied. In this manuscript, the production of bioethanol from mucilage was performed both in shake flasks and 5 L bio-reactors. The use of coffee mucilage provided adequate fermentable sugars, primarily glucose with additional nutrient components, and it was directly fermented into ethanol using a Saccharomyces cerevisiae strain. The initial tests at the lab scale were evaluated using a two-level factorial experimental design, and the resulting optimal conditions were applied to further tests at the 5 L bio-reactor for scale up. The highest yields of flasks and 5 L bio-reactors were 0.46 g ethanol/g sugars, and 0.47 g ethanol/g sugars after 12 h, respectively, which were equal to 90% and 94% of the theoretically achievable conversion yield of ethanol.
Journal Article