• Asian-Australasian Journal of Animal Sciences
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• v.33 no.1
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• pp.127-131
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• 2020

Objective: This study was conducted to determine catalytic properties of wheat phytase with exopolyphosphatase activity toward medium-chain and long-chain inorganic polyphosphate (polyP) substrates for comparative purpose. Methods: Exopolyphosphatase assay of wheat phytase toward polyP75 (medium-chain polyP with average 75 phosphate residues) and polyP1150 (long-chain polyP with average 1150 phosphate residues) was performed at pH 5.2 and pH 7.5. Its activity toward these substrates was investigated in the presence of Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺, or ethylenediaminetetraacetic acid (EDTA). Michaelis constant (K_m) and maximum reaction velocity (V_max) were determined from Lineweaver-Burk plot with polyP75 or polyP1150. Monophosphate esterase activity toward p-nitrophenyl phosphate (pNPP) was assayed in the presence of polyP75 or polyP1150. Results: Wheat phytase dephosphorylated polyP75 and polyP1150 at pH 7.5 more effectively than that at pH 5.2. Its exopolyphosphatase activity toward polyP75 at pH 5.2 was 1.4-fold higher than that toward polyP1150 whereas its activity toward polyP75 at pH 7.5 was 1.4-fold lower than that toward polyP1150. Regarding enzyme kinetics, K_m for polyP75 was 1.4-fold lower than that for polyP1150 while V_max for polyP1150 was 2-fold higher than that for polyP75. The presence of Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺, or EDTA (1 or 5 mM) exhibited no inhibitory effect on its activity toward polyP75. Its activity toward polyP1150 was inhibited by 1 mM of Ni²⁺ or Co²⁺ and 5 mM of Ni²⁺, Co²⁺, or Mg²⁺. Ni²⁺ inhibited its activity toward polyP1150 the most strongly among tested additives. Both polyP75 and polyP1150 inhibited the monophosphate esterase activity of wheat phytase toward pNPP in a dose-dependent manner. Conclusion: Wheat phytase with an unexpected exopolyphosphatase activity has potential as a therapeutic tool and a next-generational feed additive for controlling long-chain polyP-induced inappropriate inflammation from Campylobacter jejuni and Salmonella typhimurium infection in public health and animal husbandry.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.423-428
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• 2015

The machinability of materials is an important factor in engineering applications. Many ceramic components that have complex shapes require machining, typically using diamond tools, which leads to high production cost. Machinable ceramics containing h-BN have recently been developed, but these materials are very expensive because of high cost of raw materials and machining. Therefore the development of low-cost machinable ceramics is desirable. In this study, mullite-$ZrO_2$ ceramics were prepared additions of $Al_2TiO_5$. $ZrSiO_4$, $Al_2O_3$, and $Al_2TiO_5$ powders mixed at various molar ratios with sintering at 1400, 1500, and $1600^{\circ}C$ for 1 hr. Phase formation and microstructure of the sintered ceramics were observed by XRD and SEM, respectively. The machinability of each specimen was tested using the micro-hole machining method. The machinability results show that the ceramics sintered at temperatures over $1500^{\circ}C$ can be used as good low-cost machinable mullite-$ZrO_2-Al_2TiO_5$ ceramics.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.4
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• pp.363-372
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• 2020

Gardenia jasminoides (GJ) is a widely used herbal medicine with anti-inflammatory properties, but its effects on the ORAI1 channel, which is important in generating intracellular calcium signaling for T cell activation, remain unknown. In this study, we investigated whether 70% ethanolic GJ extract (GJ_EtOH) and its subsequent fractions inhibit ORAI1 and determined which constituents contributed to this effect. Whole-cell patch clamp analysis revealed that GJ_EtOH (64.7% ± 3.83% inhibition at 0.1 mg/ml) and all its fractions showed inhibitory effects on the ORAI1 channel. Among the GJ fractions, the hexane fraction (GJ_HEX, 66.8% ± 9.95% at 0.1 mg/ml) had the most potent inhibitory effects in hORAI1-hSTIM1 co-transfected HEK293T cells. Chemical constituent analysis revealed that the strong ORAI1 inhibitory effect of GJ_HEX was due to linoleic acid, and in other fractions, we found that genipin inhibited ORAI1. Genipin significantly inhibited I_ORAI1 and interleukin-2 production in CD3/CD28-stimulated Jurkat T lymphocytes by 35.9% ± 3.02% and 54.7% ± 1.32% at 30 μM, respectively. Furthermore, the same genipin concentration inhibited the proliferation of human primary CD4⁺ T lymphocytes stimulated with CD3/CD28 antibodies by 54.9% ± 8.22%, as evaluated by carboxyfluorescein succinimidyl ester assay. Our findings suggest that genipin may be one of the active components of GJ responsible for T cell suppression, which is partially mediated by activation of the ORAI1 channel. This study helps us understand the mechanisms of GJ in the treatment of inflammatory diseases.

• Journal of Electrochemical Science and Technology
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• v.8 no.1
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• pp.61-68
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• 2017

Electrochemical conversion of $CO_2$ and production of $H_2$ were attempted on a three-dimensionally ordered, porous metal organic framework (MOF-74) in which transition metals (Co, Ni, and Zn) were impregnated. A lab-scale proton exchange membrane-based electrolyzer was fabricated and used for the reduction of $CO_2$. Real-time gas chromatography enabled the instantaneous measurement of the amount of carbon monoxide and hydrogen produced. Comprehensive calculations, based on electrochemical measurements and gaseous product analysis, presented a time-dependent selectivity of the produced gases. M-MOF-74 samples with different central metals were successfully obtained because of the simple synthetic process. It was revealed that Co- and Ni-MOF-74 selectively produce hydrogen gas, while Zn-MOF-74 successfully generates a mixture of carbon monoxide and hydrogen. The results indicated that M-MOF-74 can be used as an electrocatalyst to selectively convert $CO_2$ into useful chemicals.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.11
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• pp.1686-1689
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• 2003

The ability of ten probiotic bacteria to bind a common food carcinogen aflatoxin $G_1$,$G_2$ and $B_2$ was assessed. The strains were incubated in vitro with aflatoxins and the toxin residues in the supernatant were measured using high performance liquid chromatography. The aflatoxin $G_1$ binding capacity of the strains was found to strain dependent, most efficient binding of AF$G_1$ was observed by L. acidophilus CU028 and L. brevis CU06 which bound approximately 50%. L. acidophilus CU028 was capable of bind approximately 67% of AF$G_2$, difference in their binding ability showed statistical significance (p>0.05). L. acidophilus CU028 and L. helveticus CU 631 were the best binders and the strains were observed to possess variable AF$B_2$-binding ability in the range was from 38.0% to 55.9%. Lactobacillus acidophilus CU028 was the best common binders of the three types of food carcinogen aflatoxins. The application of binding phenomenon in the removal of mycotoxins from contaminated feeds is urgently needed to improve the safety of feeds.

• Korean Journal of Environmental Biology
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• v.38 no.3
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• pp.404-415
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• 2020

We investigated the seasonal variations in growth and physiological responses of the kelp species Ecklonia cava to different nitrogen sources to establish indoor culture conditions for mass production. Ecklonia cava was cultivated for 10 days in 16 combinations of seawater temperatures (15, 17, 21, and 25℃) and different nitrogen sources (control; NH-NH₄⁺ 100 μM; NO-NO₃^- 100 μM; and NHNO-NH₄⁺ 50 μM+NO₃^- 50 μM). The growth and growth rate of the blade were affected by temperature. The mean fresh weight and area-based daily growth rate were the highest (5.8±0.5 and 6.6±0.5% day^-1, respectively) at 15℃ and the lowest (2.2±0.2 and 3.0±0.3% day^-1, respectively) at 25℃. The daily growth rate was the highest in the NH and NO treatments and lowest in the control. The nitrate reductase activity of E. cava varied with water temperature (season). The highest activity was in the control (1.32±0.10 μmol NO₂^- g^-1 dry weight h^-1) and the lowest was in the NH treatment (0.25±0.02 μmol NO₂^- g^-1 dry weight h^-1). The photosynthetic pigment concentrations reached a maximum value in the NHNO treatment and a minimum value in the control. These results showed that water temperature played an important role in the cultivation of E. cava and that a single supply of NH₄⁺ or NO₃^- may induce the accelerated growth of E. cava. The growth and physiological responses of E. cava to different nitrogen sources during each season provide valuable information for determining the optimal nitrogen source in E. cava cultivation under indoor conditions.

• Journal of Radiation Industry
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• v.8 no.1
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• pp.35-42
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• 2014

This study was conducted to analyze the protective capacity of cyanidin-3-glucoside (C3G), which is rich in mulberry and blackberry as an anthocyanin pigment. In this study, we found that treatment with C3G significantly reduced ROS production in hydrogen peroxide $(H_2O_2)-treated$ HepG2 cells in a dose-dependent manner. In addition, treatment with C3G significantly increased the cell viability in a dose-dependent manner in $H_2O_2-treated$ HepG2 cells. Moreover, treatment with C3G dose-dependently decreased the release of LDH and activation of caspase-3 in HepG2 cells treated with $H_2O_2$. Furthermore, the DNA damage in $H_2O_2-treated$ HepG2 cells was decreased by C3G treatment when compared with the control group in a dose-dependent manner. Additionally, treatment with C3G recovered the activity of antioxidant enzymes such as superoxide dismutase and catalase in $H_2O_2-treated$ HepG2 cells. To summarize, these results suggest that C3G protects cells from $H_2O_2-induced$ oxidative damage by activating antioxidant enzymes.

• Transactions of the Korean hydrogen and new energy society
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• v.12 no.3
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• pp.219-229
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• 2001

Hydrogen production by a 2-step water-splitting thermochemical cycle using metal oxides (ferrites) redox pairs and $CH_4$ have been studied in this experiment. The ferrites were reacted with $CH_4$ at $700{\sim}800^{\circ}C$ to produce CO, $H_2$ and various reduced phases (reduction step); these were then reoxidized with water vapor to generate $H_2$ in water-splitting step (oxidation step) at $600{\sim}700^{\circ}C$. The reduced ferrites, Ni-FeO and Ni-Fe alloy showed respectively different reactivity for $H_2$ formation from $H_2O$. In reduction reaction at $800^{\circ}C$, carbon was deposited on surface of Ni-ferrite due to $CH_4$ decomposition. This reduced phase containing carbon, which was taken quite different feature from other phase, produced $H_2$, CO, $CO_2$ by reacting with $H_2O$ at $600^{\circ}C$. The amount of $H_2$ evolved using reduced phase containing carbon was much higher than that of other phase.

• Applied Chemistry for Engineering
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• v.32 no.5
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• pp.487-496
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• 2021

Microalgae is one of the promising biodiesel feedstock with high growth rates compared to those of terrestrial oil crops. Despite its numerous advantages, biodiesel production from microalgae needs to reduce energy demand and material costs further to go to commercialization. During solvent extraction of microalgal lipids, lipid-extracted algae (LEA) cell residue is generated as an organic solid waste, about 80-85% of original algal biomass, and requires an appropriate recycling or economic disposal. The resulting LEA still contains significant amount of carbohydrates, proteins, N, P, and other micronutrients. This review will focus on recent advancement in the utilization of LEA as: (i) utilization as nutrients or carbon sources for microalgae and other organisms, (ii) anaerobic digestion to produce biogas or co-fermentation to produce CH₄ and H₂, and (iii) conversion to other forms of biofuel through thermochemical degradation processes. Possible mutual benefits in the integration of microalgae cultivation-biodiesel production-resulting LEA with anaerobic digestion and thermochemical conversion are also discussed.

• Journal of Applied Biological Chemistry
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• v.64 no.3
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• pp.317-322
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• 2021

Among the different cardiovascular disorders (CVDs), the activation of platelets is a necessary step. Based on this knowledge, therapeutic treatments for CVDs that target the disruption of platelet activation are proving to be worthwhile. One such substance, a bioactive 6,7-dihydroxy derived from coumarin, is 6,7-Dihydroxy-2H-1-benzopyran-2-one (esculetin). This compound has demonstrated several pharmacological effects on CVDS as well as various other disorders including diabetes, obesity, and renal failure. In various reports, esculetin and its effect has been explored in experimental mouse models, human platelet activation, esculetin-inhibited collagen, and washed human platelets exhibiting aggregation via arachidonic acid. Yet, esculetin affected aggregation with agonists like U46619 or thrombin in no way. This study investigated esculetin and how it affected human platelet aggregation activated through U46619. Ultimately, we confirmed that esculetin had an effect on the aggregation of human platelets when induced from U46619 and clarified the mechanism. Esculetin interacts with the downregulation of both phosphoinositide 3-kinase/Akt and mitogen-activated protein kinases, important phosphoproteins that are involved in activating platelets and their signaling process. The effects of esculetin reduced TXA₂ production, phospholipase A₂ activation, and platelet secretion of intracellular granules (ATP/serotonin), ultimately causing inhibition of overall platelet aggregation. These results clearly define the effect of esculetin in inhibiting platelet activity and thrombus formation in humans.