• Journal of Soil and Groundwater Environment
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• v.17 no.2
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• pp.15-21
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• 2012

MTBE (Methyl tertiary-butyl ether) has been commonly used as an octane enhancer to replace tetraethyl lead in gasoline, because MTBE increases the efficiency of combustion and decreases the emission of carbon monoxide. However, MTBE has been found in groundwater from the fuel spills and leaks in the UST (Underground Storage Tank). Fenton's oxidation, an advanced oxidation catalyzed with ferrous iron, is successful in removing MTBE in groundwater. However, Fenton's oxidation requires the continuous addition of dissolved $Fe^{2+}$. Zero-valent iron is available as a source of catalytic ferrous iron of MFO (Modified Fenton's Oxidation) and has been studied for use in PRBs (Permeable Reactive Barriers) as a reactive material. Therefore, this study investigated the condition of optimization in MFO-PRBs using waste zero-valent iron (ZVI) with the waste steel scrap to treat MTBE contaminated groundwater. Batch tests were examined to find optimal molar ratio of MTBE : $H_2O_2$ on extent to degradation of MTBE in groundwater at pH 7 with 10% waste ZVI. As the results, the ratio of optimization of MTBE to hydrogen peroxide for MFO was determined to be 1:300[mM]. The column experiment was conducted to know applicability of MFO-PRBs for MTBE remediation in groundwater. As the results of column test, MTBE was removed 87% of the initial concentration during 120days of operational period. Interestingly, MTBE was degraded not only within waste ZVI column but also within sand column. It means the aquifer may affect continuously the MTBE contaminated groundwater after throughout the waste ZVI barrier. The residual products showed acetone, TBF (Tert-butyl formate) and TBA (Tert-butyl acetate) during this test. The results of the present study showed that the recycled materials can be effectively used for not only a source of catalytic ferrous iron but also a reactive material of the MFO-PRBs to remove MTBE in groundwater.

• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.808-817
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• 2011

Because of its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum has a considerable potential in biomass hydrolysis applications. Trichoderma harzianum cellobiohydrolase I (ThCBHI), an exoglucanase, is an important enzyme in the process of cellulose degradation. Here, we report an easy single-step ion-exchange chromatographic method for purification of ThCBHI and its initial biophysical and biochemical characterization. The ThCBHI produced by induction with microcrystalline cellulose under submerged fermentation was purified on DEAE-Sephadex A-50 media and its identity was confirmed by mass spectrometry. The ThCBHI biochemical characterization showed that the protein has a molecular mass of 66 kDa and pI of 5.23. As confirmed by smallangle X-ray scattering (SAXS), both full-length ThCBHI and its catalytic core domain (CCD) obtained by digestion with papain are monomeric in solution. Secondary structure analysis of ThCBHI by circular dichroism revealed ${\alpha}$- helices and ${\beta}$-strands contents in the 28% and 38% range, respectively. The intrinsic fluorescence emission maximum of 337 nm was accounted for as different degrees of exposure of ThCBHI tryptophan residues to water. Moreover, ThCBHI displayed maximum activity at pH 5.0 and temperature of $50^{\circ}C$ with specific activities against Avicel and p-nitrophenyl-${\beta}$-D-cellobioside of 1.25 U/mg and 1.53 U/mg, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.4013-4018
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• 2014

A 0.45 $cm^2$ DSSC device with a glass/FTO/blocking layer/$TiO_2$/N719(dye)/electrolyte/50 nm-Pt/50 nm-Au/FTO/glass was prepared to examine the stability of the Au/Pt bilayered counter electrode (CE) with electrolyte and the energy conversion efficiency (ECE) of dye-sensitized solar cells (DSSCs). For comparison, a 100 nm-thick Pt only CE DSSC was also prepared using the same method. The photovoltaic properties, such as the short circuit current density ($J_{sc}$), open circuit voltage ($V_{oc}$), fill factor (FF), and ECE, were checked using a solar simulator and potentiostat with time after assembling the DSSC. The microstructure of the Au/Pt bilayer was examined by optical microscopy after 0~25 minutes. The ECE of the Pt only CE-employed DSSC was 4.60 %, which did not show time dependence. On the other hand, for the Au/Pt CE DSSC, the ECEs after 0, 5 and 15 minutes were 5.28 %, 3.64 % and 2.09 %, respectively. The corrosion areas of the Au/Pt CE determined by optical microscopy after 0, 5, and 25 minutes were 0, 21.92 and 34.06 %. These results confirmed that the ECE and catalytic activity of Au/Pt CE decreased drastically with time. Therefore, a Au/Pt CE-employed DSSC may be superior to the Pt only CE-employed one immediately after integration of the device, but it would degrade drastically with time.

• Journal of Microbiology and Biotechnology
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• v.23 no.11
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• pp.1519-1528
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• 2013

Bacillus pumilus SG2, a halotolerant strain, expresses two major chitinases designated ChiS and ChiL that were induced by chitin and secreted into the supernatant. The present work aimed to obtain a mutant with higher chitinolytic activity through mutagenesis of Bacillus pumilus SG2 using a combination of UV irradiation and nitrous acid treatment. Following mutagenesis and screening on chitin agar and subsequent formation of halos, the mutated strains were examined for degradation of chitin under different conditions. A mutant designated AV2-9 was selected owing to its higher chitinase activity. To search for possible mutations in the whole operon including ChiS and ChiL, the entire chitinase operon, including the intergenic region, promoter, and two areas corresponding to the ChiS and ChiL ORF, was suquenced. Nucleotide sequence analysis of the complete chitinase operon from the SG2 and AV2-9 strains showed the presence of a mutation in the catalytic domain (GH18) of chitinase (ChiL). The results demonstrated that a single base change had occurred in the ChiL sequence in AV2-9. The wild-type chitinase, ChiL, and the mutant (designated ChiLm) were cloned, expressed, and purified in E. coli. Both enzymes showed similar profiles of activity at different ranges of pH, NaCl concentration, and temperature, but the mutant enzyme showed approximately 30% higher catalytic activity under all the conditions tested. The results obtained in this study showed that the thermal stability of chitinase increased in the mutant strain. Bioinformatics analysis was performed to predict changes in the stability of proteins caused by mutation.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.731-738
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• 2011

In this study AOPs of $O_3/UV$ radiation, $O_3/Mg(OH)_2/UV$ radiation and $O_3/MgO/UV$ radiation system for phenol treatment in aqueous solution was performed in a laboratory scale circulating batch reacter. Flow rate of ozone 1.0 L/min, ozone concentrations $150{\pm}10mg/L$ was maintained constantly at the above-mentioned oxidation processes. During the oxidation processes the $COD_{Cr}$ and TOC was measured in the composition. The pseudo first-order rate constants of the processes was $5.12{\times}10^{-5}$, $1.19{\times}10^{-4}$ and $1.79{\times}10^{-4}sec^{-1}$, and the activation energy was 3.03, 1.79 and $2.32kcal{\cdot}mol^{-1}$ at $20^{\circ}C$, respectively. It was found that both $Mg(OH)_2$ and MgO had remarkable accelerations on degradation of phenol and removal of COD in water. On this basis, $O_3/MgO/UV$ system is an effective and feasible routes for catalytic ozonation of phenol in water.

• Journal of Surface Science and Engineering
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• v.56 no.6
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• pp.412-419
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• 2023

Anion exchange membrane electrolysis is considered a promising next-generation hydrogen production technology that can produce low-cost, clean hydrogen. However, anion exchange membrane electrolysis technology is in its early stages of development and requires intensive research on electrodes, which are a key component of the catalyst-system interface. In this study, we optimized the pressure conditions of the hot-pressing process to manufacture cobalt oxide electrodes for the development of a high uniformity and high adhesion electrode production process for the oxygen evolution reaction. As the pressure increased, the reduction of pores within the electrode and increased densification of catalytic particles led to the formation of a uniform electrode surface. The cobalt oxide electrode optimized for pressure conditions exhibited improved catalytic activity and durability. The optimized electrode was used as the anode in an AEMWE single cell, exhibiting a current density of 1.53 A cm^-2 at a cell voltage of 1.85 V. In a durability test conducted for 100 h at a constant current density of 500 mA cm^-2, it demonstrated excellent durability with a low degradation rate of 15.9 mV kh^-1, maintaining 99% of its initial performance.

• Membrane Journal
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• v.27 no.4
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• pp.328-335
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• 2017

Fabricating photocatalytic composite membrane with a mesoporous and tailored morphological structure would have significant implication for environmental remediation. In this study, we reported hybrid $TiO_2$ immobilized photocatalytic membrane and its application for the treatment of dye solution. Photocatalytic film with high porosity and homogeneity was fabricated by graft copolymer as polymer template. Hybridization of membrane filtration with photocatalysis was successfully achieved by photocatalytic membrane reactor developed. Result showed that membrane permeability was significantly reduced after immobilizing the $TiO_2$ film on bare $Al_2O_3$ support. The membrane characterization indicated that well organized $TiO_2$ film was successfully formed on $Al_2O_3$ support. Benefiting from the controlled morphology of $TiO_2$ film, the composite membrane exhibited almost complete degradation of organic dye within 5 h of filtration under UV illumination. Langmuir-Hinshelwood model explained degradation of organic dye. First-order rate constant was approximately six times with $TiO_2$ immobilized composite ceramic membrane, higher than the one with the bare $Al_2O_3$ support (0.0081 vs. $0.0013min^{-1}$).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.474-481
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• 2018

The policy-making and technological development of eco-friendly automobiles designed to increase their supply is ongoing, but the internal combustion engine still accounts for approximately 95% of automobiles in use. To meet the stricter emission regulations of internal combustion engines based on fossil fuels, the proportion of after-treatments for vehicles and (ocean going) vessels is increasing continuously. As diesel engines have high power and good fuel economy in addition to less CO2 emissions, their market share is increasing not only in commercial vehicles, but also in passenger cars. Because of the characteristics of the diesel combustion, however, NOx is generated in localized high-temperature combustion regions, and particulates are formed in the zones of diffusion combustion. LNT and urea-SCR catalysts have been developed for the after-treatment of exhaust gas to reduce NOx in diesel vehicles. This study examined the effect of a containing promoter on SCR catalysts to cope with the severe exhaust gas regulation. The de-NOx performance of the Mn-SCR catalyst was the best, and the de-NOx performance was improved as the ion exchange rate between Mn ion and Zeolyst was good and the activation energy was low. The de-NOx performance of the 7Cu-15Ba/78Zeoyst catalyst was 32% at $200^{\circ}C$ and 30% at $500^{\circ}C$, and showed the highest performance. The NOx storage material of BaO loaded as a promoter was well dispersed in the Cu-SCR catalyst and the additional de-NOx performance of BaO was affected by the reduction reaction of the Cu-SCR catalyst. Among the three catalysts, the 7Cu-15Ba/Zeolyst SCR catalyst was resistant to thermal degradation. The same type of CuO due to thermal degradation migrates and agglomerates because BaO reduces the agglomeration of the main catalyst CuO particles.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1753-1758
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• 2012

A novel, efficient and controlled protocol for the synthesis and enhanced photocatalytic activity of $Au@TiO_2$ nanocomposite is developed. $TiO_2$ (P25) was pretreated by employing UV light (${\lambda}$ = 254 nm) and the pretreated $TiO_2$ was uniformly decorated by gold nanoparticles (AuNPs) in presence of sodium citrate and UV light. UV pretreatment makes the $TiO_2$ activated, as electrons were accumulated within the $TiO_2$ in the conduction band. These accumulated electrons facilitate the formation of AuNPs which were of very small size (2-5 nm), similar morphology and uniformly deposited at $TiO_2$ surface. It leads to formation of stable and crystalline $Au@TiO_2$ nanocomposites. The rapidity (13 hours), monodispersity, smaller nanocomposites and easy separation make this protocol highly significant in the area of nanocomposites syntheses. As-synthesized nanocomposites were characterized by TEM, HRTEM, TEM-EDX, SAED, XRD, UV-visible spectrophotometer and zeta potential. Dye degradation experiments of methyl orange show that type I ($Au@TiO_2$ nanocomposites in which $TiO_2$ was pretreated with UV light) has enhanced photocatalytic activity in comparison to type II ($Au@TiO_2$ nanocomposites in which $TiO_2$ was not pretreated with UV light) and $TiO_2$ (P25). This shows that pretreatment of $TiO_2$ provides type I a better catalytic activity.

• Journal of Life Science
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• v.28 no.6
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• pp.753-763
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• 2018

Cysteine cathepsins are lysosomal enzymes that belong to the papain family and can induce the degradation of damaged proteins through the endo-lysosomal pathway. It is highly upregulated in many cancers by regulating gene amplification and transcriptional, translational, and post-transcriptional modifications. Cathepsin S is part of the cysteine cathepsin family. Many studies have demonstrated that cathepsin S not only plays a specific role in MHC class II antigen presentation but also plays a crucial role in cancers. Cathepsin S is more stable at a neutral pH compared to other cysteine cathepsins, which supports the importance of cathepsin S in disease microenvironments. Therefore, the dysregulation of cathepsin S has participated in a variety of pathological processes, including cancer, arthritis, and cardiovascular disease. Furthermore, a decrease or depletion in the expression of cathepsin S has been implicated in the processes of tumor growth, invasion, metastasis, and angiogenesis. Taken together, cathepsin S has been suggested as an attractive therapeutic target for cancer therapy. In this review, the known involvement of cathepsin S in diseases, particularly with respect to recent work indicating its role in cancer therapy, is examined. An overview of current literature on the inhibitors of cathepsin S as a therapeutic target for cancer is also provided.