• 한국축산식품학회지
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• 제35권6호
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• pp.800-806
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• 2015

We investigated the effects of a pulsed electric field (PEF) treatment on microbial inactivation and the physical properties of low-fat milk. Milk inoculated with Escherichia coli, Saccharomyces cerevisiae, or Lactobacillus brevis was supplied to a pilot-scale PEF treatment system at a flow rate of 30 L/h. Pulses with an electric field strength of 10 kV/cm and a pulse width of 30 µs were applied to the milk with total pulse energies of 50-250 kJ/L achieved by varying the pulse frequency. The inactivation curves of the test microorganisms were biphasic with an initial lag phase (or shoulder) followed by a phase of rapid inactivation. PEF treatments with a total pulse energy of 200 kJ/L resulted in a 4.5-log reduction in E. coli, a 4.4-log reduction in L. brevis, and a 6.0-log reduction in S. cerevisiae. Total pulse energies of 200 and 250 kJ/L resulted in greater than 5-log reductions in microbial counts in stored PEF-treated milk, and the growth of surviving microorganisms was slow during storage for 15 d at 4℃. PEF treatment did not change milk physical properties such as pH, color, or particle-size distribution (p<0.05). These results indicate that a relatively low electric-field strength of 10 kV/cm can be used to pasteurize low-fat milk.

• 한국물환경학회지
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• 제26권6호
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• pp.1028-1033
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• 2010

Wastewater reuse for agricultural irrigation needs treatment and control of pathogens to minimize risks to human health and the environment. In order to evaluate the water quality of UV-treated reclaimed water, this study focused on the relationship between micro-pathogens and particulate matters. MS2 was selected as an index organism because it has similar characteristics to human enteric virus and strong resistance to UV disinfection. The turbidity and suspended solid (SS) were selected for test parameters. In this study, it was performed with different UV doses (30 and $60mJ/cm^2$) for estimation of the MS2 inactivation rate using collimated beam batch experiments in the laboratory. The experiment results by turbidity or SS concentration presented that the increased concentration of them lowered MS2 inactivation. At the turbidity (below 4.27 NTU) and SS (below 1.47 mg/L) of the low level range, the inactivation of 60 UV dose is higher than 30 UV dose. However, at the turbidity and SS of the high level, the increasing UV dose did not show apparent increasing the MS2 inactivation. In quantitative microbial risk assessment (QMRA), it can confirm the trend that $P_D$ and turbidity concentrations have positive correlationship at the low concentration, which was also observed in SS. The QMRA can be helpful in communication with public for safe wastewater reuse and be recommended.

• 상하수도학회지
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• 제30권2호
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• pp.139-145
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• 2016

Disinfection of microorganisms using UV light is widely used in the field of water supply and wastewater treatment plant, In spite of high germicidal effect and relatively clean by-product, UV disinfection has fundamental defeat that is accumulation of fouling materials at the interface of water and lamp sleeve. Non-contact type of UV photoreactor which can avoid this fouling generation was developed and the experimental performance evaluation of the system was carried out in this study. Log inactivation rate of E. coli was selected as a disinfection index. The concentration of E. coli of second clarifier effluent was $8.2{\times}10^1-8.2{\times}10^3$ colony per mL and was well inactivated by the non-contact type of UV photoreactor. Under the UV intensity condition of $2.1-2.5mW/cm^2$, E. coli removal rate was observed in the range of 54 - 95% when the HRT was increased from 10 to 52 seconds. Experimental results showed that log inactivation of E. coli was proportional to UV dosage and $200mJ/cm^2$ of UV dose is expected for the 2.0 log inactivation of E. coli from the second clarifier effluent. Between the two parameters of UV intensity and contact time which are consist of UV dose, UV intensity was 4 times more effective than contact time.

• BMB Reports
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• 제28권2호
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• pp.112-117
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• 1995

Succinic semialdehyde reductase was inactivated by o-phthalaldehyde. The inactivation followed pseudo-first order kinetics, and the second-order rate constant for the inactivation process was 28 $M^{-1}s^{-1}$ at pH 7.4 and $25^{\circ}C$. The absorption spectrum ($\lambda_{max}$ 337 nm) and fluorescence excitation ($\lambda_{max}$ 340 nm) and fluorescence emission spectra ($\lambda_{max}$ 409 nm) were consistent with the formation of an isoindole derivative in the catalytic site between a cysteine and a lysine residue approximately about 3 $\AA$ apart. The substrate, succinic semialdehyde, did not protect enzymatic activity against inactivation, whereas the coenzyme NADPH protected against o-phthaladehyde induced inactivation of the enzyme. About 1 isoindole group per mol of the enzyme was formed following complete loss of enzymatic activity. These results suggest that the amino acid residues of the enzyme participating in a reaction with o-phthalaldehyde are cysteinyl and lysyl residues at or near the NADPH binding site.

• Environmental Engineering Research
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• 제12권2호
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• pp.64-71
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• 2007

The necessity of disinfecting playground soil is an important issue, because pathogenic protozoa, bacteria, and parasite eggs remain viable for several months and can infect children. UV irradiation has been used to decontaminate water but its effectiveness on soil is unclear. We determined the efficacy of UV radiation for inactivation of an indicator bacteria, E. coli (strain ATCC 8739), on playground soil. While 99% inactivation of E. coli in the soil was readily achieved by UV radiation within 55 min at $0.4\;mW\;cm^{-2}$, complete inactivation was not achieved, even after prolonged treatment at $4\;mW\;cm^{-2}$. This was attributed to the irregular surface of the soil. A small number of E. coli escaped the UV radiation because they were situated in indentations or under small particles on the soil surface. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) confirmed that the surface characteristics of the soil is the major limiting factor in the inactivation of E. coli by UV radiation. Thus UV treatment may not be adequate for disinfecting some soils and should be carefully evaluated before being used on playground soils.

• International Journal of Oral Biology
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• 제33권2호
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• pp.51-58
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• 2008

A mutation of UNCL, an inner nuclear membrane RNAbinding protein, has been found to eliminate mechanotransduction in Drosophila. UNCL is expressed in human periodontal tissue including in periodontal ligament (PDL) fibroblasts. However, it is unclear how a mechanical stimulus is translated into cellular responses in PDL fibroblasts. The aim of this study was to evaluate the effect of UNCl on mechanical stress related genes in PDL fibroblasts in response to mechanical stress. The mRNA of TGF-$\beta$, COX-2, and MMP-2 was up-regulated after UNCL inactivation in PDL fibroblasts under the compression force. Under the tensile force, inactivation of UNCL decreased the expression of Biglycan, RANKL, MMP-2, and TIMP-2 mRNAs while it increased the expression of TIMP-1. p38-MAPK was expressed in PDL fibroblasts under compression forces whereas phospho-ERK1/2, p65-NFkB, and c-fos were expressed under tension forces. The expression and phosphorylation of the mechanical stress related genes, kinases, and transcription factors were changed according to the types of stress. Furthermore, most of them were regulated by the inactivation of UNCL. This suggests that UNCL is involved in the regulation of mechanical stress related genes through the signaling pathway in PDL fibroblasts.

• BMB Reports
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• 제28권1호
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• pp.72-78
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• 1995

Time-dependent inactivation of E. coli GTP cyclohydrolase I with a 2',3'-dialdehyde derivative of GTP (oGTP) was directed to the active site of the enzyme, and was dependent on the concentration of oGTP. The kinetics of inactivation were biphasic with a rapid reaction occurring immediately upon exposure of the enzyme to oGTP followed by a slow rate of inactivation. The $K_i$ value of oGTP for the enzyme was 0.25 mM. Inactivation was prevented by preincubation of the enzyme with GTP, the substrate of the enzyme. At 100% inactivation, 2.3 mol of [8.5'-$^3H$]oGTP were bound per each enzyme subunit, which consists of two identical polypeptides. The active site residue which reacted with the affinity label was lysine. oGTP interacted selectively with the ${\varepsilon}$-amino group of lysine in the GTP-binding site to form a morpholine-like structure which was stable without sodium borohydride treatment. However, triphosphate group was eliminated during the hydrolysis step. To identify the active site of the enzyme, [8.5'-$^3H$]oGTP-labeled enzyme was cleaved by endoproteinase Lys-C, and the $^3H$-labeled peptide was purified by HPLC. The amino acid sequence of the active site peptide was Pro-Ser-Leu-Ser-Lys, which corresponds to the aminoterminal sequence of the enzyme.

• 한국미생물·생명공학회지
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• 제11권3호
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• pp.155-161
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• 1983

Bacteriophage f2에 대한 자외광선의 살균효과와 외투막 단백질의 구조에 미치는 영향을 Ray-onet photoreactor PPR-208을 사용하여 300nm의 광선으로 연구하였다. 처음 20분간의 조사에서는 약 4 log의 phage가 감소되고 그후 완만한 살균효과를 보이다가 90분 이상의 조사에서는 생존 바이러스가 발견되지 않았다. Tryptophan residue의 fluorescenve quenching, 자외선으로 조신한 phage에 부착시킨 ANS (8-anilino-1-napht-halene sulfonate)의 fluorescence emission의 감소, tryptophan에서 ANS로의 energy transfer 의 감소 등 spectroscopic technique에 의한 결과와 자외선 조사에 의하여 단백질 외투만이 파손되는 전자현미경 관찰의 결과에 의하여 자외광선은 phage f2의 외투막 단백질의 구조에 변화를 일으킨다는 것이 밝혀졌다.

• 한국식품과학회지
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• 제28권3호
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• pp.587-592
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• 1996

과일쥬스의 변패에 관여하는 Candida tropicalis에 대하여 고압처리에 의한 사멸과 미생물의 미세구조에 미치는 압력의 영향을 조사하였다. C. tropicalis의 가압사멸은 1차 반응을 따르며, $25^{\circ}C-400\;MPa$에서 D값은 1.4분이었고, z값은 100 MPa이었다. 고압처리에 의한 살균효과는 $25^{\circ}C$에서보다 $45^{\circ}C$에서 높게 나타났다. $25^{\circ}C$에서 400MPa, 10분 고압처리로 C. tropicalis는 미토콘드리아막과 세포벽이 변형되었다. 다라서 고압처리에 의한 세포막, 원형질막 등의 변형이 미생물 가압사멸의 원인이 되는 것으로 판단된다.

• 한국식품과학회지
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• 제29권6호
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• pp.1202-1207
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• 1997

가열 살균을 대체하여 식품의 신선도를 유지하면서 효과적으로 미생물을 사멸시킬 수 있는 새로운 비가열 살균기술로서 고압 $CO_2$, 처리를 고찰하고자 하였다. 이를 위해 김치에서 분리한 Leuconostoc sp.를 대상 미생물로 가압 조절인자를 달리하여 이 균주에 미치는 고압 $CO_2$의 살균 효과를 검토하였다. 사용 압력과 온도, 처리시간이 증가할수록, 이에 반해 작업용량은 감소할수록 균체의 사멸율이 증가하였으며, $30^{\circ}C$, $60\;kg/cm^2$의 $CO_2$가압 조건에서 젖산균 배양액을 $10^{-3}$만큼 감균하는데 약 150분이 소요되었다. 실험 결과로부터 고압 $CO_2$에 의한 미생물 살균은 기본적으로 $CO_2$의 세포내 침투에 의해 좌우되며, 따라서 세포 내부로의 $CO_2$ 전달 과정이 전체적인 살균 효율을 결정짓는 가장 중요한 단계임을 확인할 수 있었다.