• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.337-345
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• 2021

Lipase (triacylglycerol lipase, EC 3.1.1.3) is an enzyme capable of hydrolyzing triacylglycerol, to produce fatty acids and glycerol and reverse the reaction of triacylglycerol synthesis from fatty acids and glycerol through transesterification. Applications of lipase are quite widespread in the industrial sector, including in the detergent, paper, dairy, and food industries, as well as for biodiesel synthesis. Lipases by yeasts have attracted industrial attention because of their fast production times and high stability. In a previous study, a lipase-producing yeast isolate was identified as Zygosaccharomyces mellis SG1.2 and had a productivity of 24.56 U/mg of biomass. This productivity value has the potential to be a new source of lipase, besides Yarrowia lypolitica which has been known as a lipase producer with a productivity of 0.758 U/mg. Lipase production by Z. mellis SG1.2 needs to be increased by optimizing the production medium. The aims of this study were to determine the significant component of the medium for lipase production and methods to increase lipase production using the optimum medium. The two methods used for the statistical optimization of production medium were Taguchi and RSM (Response Surface Methodology). The data obtained were analyzed using Minitab 18 and SPSS 23 software. The most significant factors which affected lipase productivity were olive oil and peptones. The optimum medium composition consisted of 1.02% olive oil, 2.19% peptone, 0.05% MgSO₄·7H₂O, 0.05% KCl, and 0.2% K₂HPO₄. The optimum medium was able to increase the lipase productivity of Z. mellis SG1.2 to 1.8-fold times the productivity before optimization.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2921-2926
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• 2009

Cu-BTC[$Cu_3(BTC)_2(H_2O)_3$, BTC = 1,3,5-benzenetricarboxylate], one of the most well-known metal-organic framework materials (MOF), has been synthesized under atmospheric pressure and room temperature by using ultrasound. The Cu-BTC can be obtained in 1 min in the presence of DMF (N,N-dimethylformamide), suggesting the possibility of continuous production of Cu-BTC. Moreover, the surface area and pore volume show that the concentration of DMF is important for the synthesis of Cu-BTC having high porosity. The morphology and phase also depend on the concentration of DMF : Cu-BTC cannot be obtained at room temperature in the absence of DMF and aggregated Cu-BTC (with low surface area) is produced in the presence of high concentration of DMF. It seems that the deprotonation of benzenetricarboxylic acid by base (such as DMF) is inevitable for the room temperature syntheses.

• Korean Journal of Materials Research
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• v.31 no.6
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• pp.313-319
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• 2021

Understanding of effects of changes in the particle size of the matrix material on the mullite whisker growth during the production of porous mullite is crucial for better design of new porous ceramics materials in different applications. Commercially, raw materials such as Al₂O₃/SiO₂ and Al(OH)₃/SiO₂ are used as starting materials, while AlF₃ is added to fabricate porous mullite through reaction sintering process. When Al₂O₃ is used as a starting material, a porous microstructure can be identified, but a more developed needle shaped microstructure is identified in the specimen using Al(OH)₃, which has excellent reactivity. The specimen using Al₂O₃/SiO₂ composite powder does not undergo mulliteization even at 1,400 ℃, but the specimen using the Al(OH)₃/SiO₂ composite powder had already formed complete mullite whiskers from the particle size specimen milled for 3 h at 1,100 ℃. As a result, the change in sintering temperature does not significantly affect formation of microstructures. As the particle size of the matrix materials, Al₂O₃ and Al(OH)₃, decreases, the porosity tends to decrease. In the case of the Al(OH)₃/SiO₂ composite powder, the highest porosity obtained is 75 % when the particle size passes through a milling time of 3 h. The smaller the particle size of Al(OH)₃ is and the more the long/short ratio of the mullite whisker phase decreases, the higher the density becomes.

• Journal of the Korean institute of surface engineering
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• v.56 no.1
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• pp.55-61
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• 2023

As a preliminary study to produce functional nanocomposites in a heat dissipation device, we performed the direct synthesis of carbon nanotubes (CNTs) on the surface of alumina (Al₂O₃) powders. A thermal chemical vapor deposition (TCVD) system was used to grow CNTs directly on the Al₂O₃ surface. In order to investigate the growth behavior of CNTs, we varied both furnace temperature of the TCVD ranging from 700 to 850 ℃ and concentration of the ferritin-dissolved DI solution from 0.1 to 2.0 mg/mL. From the previous results, the gas composition and duration time for CNT growth were fixed as C₂H₄ : H₂ = 30 : 500 (vol. %) and 10 min, respectively. Based on the analysis results, the optimized growth temperature and ferritin concentration were found to be 825 ℃ and 0.5 mg/mL, respectively. The obtained results could be adopted to achieve mass production of nanocomposites with heat dissipation functionality.

• Journal of Life Science
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• v.33 no.12
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• pp.1002-1014
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• 2023

The root of Cirsium japonicum var. maackii (Maxim.) has long been used in traditional medicine to prevent the onset and progression of various diseases and has been reported to exert a wide range of physiological effects, including antioxidant activity. However, research on its effects on hepatocytes remains scarce. This study used the human hepatocellular carcinoma HepG2 cell line to investigate the antioxidant activity of ethanol extract of C. japonicum root (EECJ) on hepatocytes. Hydrogen peroxide (H₂O₂) was used to mimic oxidative stress. The results showed that EECJ significantly reverted the decrease in cell viability and suppressed the release of lactate dehydrogenase in HepG2 cells treated with H₂O₂. Moreover, an analysis of changes in cell morphology, flow cytometry, and microtubule-associated protein light chain 3 (LC3) expression showed that EECJ significantly inhibited HepG2 cell autophagy induced by H₂O₂. Furthermore, it attenuated H₂O₂-induced apoptosis and cell cycle disruption by blocking intracellular reactive oxygen species and mitochondrial superoxide production, indicating strong antioxidant activity. EECJ also restored the decreased levels of intracellular glutathione (GSH) and enhanced the expression and activity of superoxide dismutase and GSH peroxidase in H₂O₂-treated HepG2 cells. Although an analysis of the components contained in EECJ and in vivo validation using animal models are needed, these findings indicate that EECJ is a promising candidate for the prevention and treatment of oxidative stress-induced liver cell damage.

• Transactions of the Korean hydrogen and new energy society
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• v.10 no.2
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• pp.131-139
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• 1999

The objective of this works was to synthesize the$Mg_2Ni$ hydrogen storage materials economically and to eliminate the intial activation process. $Mg_2NiH_x$ was mechanically alloyed under purified hydrogen gas atmosphere using pure Mg and Ni chips. M.A(Mechanical Alloying) was carried out using planetary ball mill for times varying from 12h to 96h under 20bars of hydrogen gas pressure. $Mg_2NiH_x$ started to form after 48h and the homogeneous $Mg_2NiH_x$ composites was synthesized after 96h. From TG analysis, the dehydriding reaction of $Mg_2NiH_x$ started at around $200^{\circ}C$. The result of P-C-T at $300^{\circ}C$ revealed the hydrogen storage capacity of $Mg_2NiH_c$ reached 3.68 wt% and the effective hydrogen storage was 2.38 wt%. The enthalpy difference of absorption-desorption cycling for the hydride formation and the hysteresis were reduced and the plateau flatness and the sloping were improved according to M.A time.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.4
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• pp.337-344
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• 2020

Worldwide, there is a significant surge in the efforts for addressing the issue of global warming; the use of renewable energy is one of the solutions proposed to mitigate global warming. However, severe volatility is a critical disadvantage, and thus, power-to-gas technology is considered one of best solutions for energy storage. Hydrogen is a popular candidate from the perspective of both environment and economics. Accordingly, a hydrogen production system based on renewable energy sources is developed, and the economics of the system are assessed. The result of the base case shows that the unit cost of hydrogen production would be 6,415 won/kg H₂, with a hydrogen production plant based on a 100 MW akaline electrolyzer and 25% operation rate, considering renewable energy sources with no electricity cost payment. Sensitivity study results show that the range of hydrogen unit cost efficiency can be 2,293 to 6,984 Won/kg H₂, depending on the efficiency and unit cost of the electrolyzer. In case of electrolyzer operation rate and electricity unit cost, sensitivity study results show that hydrogen unit cost is in the range 934-26,180 won/kg H₂.

• Journal of Animal Science and Technology
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• v.62 no.1
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• pp.52-57
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• 2020

In rumen in vitro experiments, although nitrogen gas (N₂) flushing has been widely used, its effects on rumen fermentation characteristics are not clearly determined. The present study is the first to evaluate the effects of N₂ flushing on rumen fermentation characteristics in in vitro batch culture system by comparing with new applicable non-metabolizable gas: argon (Ar). The rumen fluid was taken from two Korean native heifers followed by incubation for 3, 9, 12, and 24 h with N₂ or Ar flushing. As a result, in all incubation time, N₂ flushing resulted in higher total gas production than Ar flushing (p < 0.01). Additionally, in N₂ flushing group, ammonia nitrogen was increased (p < 0.01). However, volatile fatty acids profiles and pH were not affected by the flushing gases (p > 0.05). In conclusion, the present study demonstrated that N₂ flushing can influence the rumen nitrogen metabolism via increased ammonia nitrogen concentration and Ar flushing can be used as a new alternative flushing gas.

• Animal Bioscience
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• v.36 no.10
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• pp.1508-1516
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• 2023

Objective: To carry out a comprehensive production planning of the existing Rongchang pig population from both environmental and genetic aspects, and to establish a closed population with stable genetic diversity and strict pathogen control, it is necessary to fully understand the genetic background of the population. Methods: We genotyped 54 specific pathogen free (SPF) Rongchang pigs using the Zhongxin-1 Porcine Breeding Array PLUS, calculated their genetic diversity parameters and constructed their families. In addition, we also counted the runs of homozygosity (ROH) of each individual and calculated the value of inbreeding coefficient based on ROH for each individual. Results: Firstly, the results of genetic diversity analysis showed that the effective population size (N_e) of this population was 3.2, proportion of polymorphic markers (P_N) was 0.515, desired heterozygosity (H_e) and observed heterozygosity (H_o) were 0.315 and 0.335. H_o was higher than H_e, indicating that the heterozygosity of all the selected loci was high. Secondly, combining the results of genomic relatedness analysis and cluster analysis, it was found that the existing Rongchang pig population could be divided into four families. Finally, we also counted the ROH of each individual and calculated the inbreeding coefficient value accordingly, whose mean value was 0.09. Conclusion: Due to the limitation of population size and other factors, the genetic diversity of this Rongchang pig population is low. The results of this study can provide basic data to support the development of Rongchang pig breeding program, the establishment of SPF Rongchang pig closed herd and its experimental utilization.

• Journal of Life Science
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• v.31 no.4
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• pp.389-399
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• 2021

This study determined the effects of Centella asiatica leaf on H₂O₂ induced cell cycle arrest, mitochondrial activity, and proinflammatory cytokine production in human dermal fibroblast (HDF) cells. We used an 80% methanol extract of C. asiatica, its ethyl acetate fraction, and asiaticoside, the major constituent of C. asiatica. The C. asiatica extract, its ethyl acetate fraction, and asiaticoside attenuated G1 cell cycle-arrest and the apoptotic effect caused by H₂O₂-induced oxidative stress. The cells treated with C. asiatica extract, its ethyl acetate fraction, and asiaticoside secreted lower levels of TNF-α and IL-6. The antioxidant effect of asiaticoside was higher than that of C. asiatica extract and its ethyl acetate fraction. Treatment with C. asiatica extract, its ethyl acetate fraction, and asiaticoside also increased the mitochondrial membrane potential and restored normal mitochondrial morphology. Following H₂O₂ stress induction, cells treated with C. asiatica extract, its ethyl acetate fraction, and asiaticoside showed increased mitochondrial oxygen consumption rates and decreases in the TLR4-MyD88-TRAF6-p65 pathway activity. These findings suggest that C. asiatica extract, its ethyl acetate fraction, and asiaticoside have antioxidant and anti-inflammatory effects, as well as the ability to control the mitochondrial activities of HDF cells.