• KSBB Journal
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• v.25 no.1
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• pp.33-40
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• 2010

Conventional disinfectants and disinfection method are expensive, hazardous and often require long periods of exposure. Recently, there is growing interest in complex disinfection process as a disinfection technique in medical instruments such as endoscope, hand piece bur to improve the disinfection efficiency and conveniency. The aim of this study was to evaluate the performance of a new complex process for the purpose of disinfection of Escherichia coli in water. Three single process (electrolysis, UV and ultrasonic process) was combined dual and triple disinfection process. The order of disinfection performance for E. coli in dual process lie in: Electrolysis + UV > Electrolysis + Ultrasonic > UV + Ultrasonic process. Disinfection efficiency of E. coli and degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicating material of OH radical formation) of dual process was higher than that of the triple process (Electrolysis + UV + Ultrasonic process). In electrolysis + UV process, disinfection tendency was well agreed with RNO degradation tendency.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.337-346
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• 2016

Three combinations of molecular chaperones from Escherichia coli (i.e., DnaK-DnaJ-GrpE-GroEL-GroES, GroEL-GroES, and DnaK-DnaJ-GrpE) were overproduced in E. coli BL21, and their in vitro stabilizing effects on a nitrile hydratase (NHase) were assessed. The optimal gene combination, E. coli groEL-groES (ecgroEL-ES), was introduced into Rhodococcus ruber TH3. A novel engineered strain, R. ruber TH3G was constructed with the native NHase gene on its chromosome and the heterologous ecgroEL-ES genes in a shuttle plasmid. In R. ruber TH3G, NHase activity was enhanced 37.3% compared with the control, TH3. The in vivo stabilizing effect of ecGroEL-ES on the NHase was assessed using both acrylamide immersion and heat shock experiments. The inactivation behavior of the in vivo NHase after immersion in a solution of dynamically increased concentrations of acrylamide was particularly evident. When the acrylamide concentration was increased to 500 g/l (50%), the remaining NHase activity in TH3G was 38%, but in TH3, activity was reduced to 10%. Reactivation of the in vivo NHases after varying degrees of inactivation was further assessed. The activity of the reactivated NHase was more than 2-fold greater in TH3G than in TH3. The hydration synthesis of acrylamide catalyzed by the in vivo NHase was performed with continuous acrylonitrile feeding. The final concentration of acrylamide was 640 g/l when catalyzed by TH3G, compared with 490 g/l acrylamide by TH3. This study is the first to show that the chaperones ecGroEL-ES work well in Rhodococcus and simultaneously possess protein-folding assistance functions and the ability to stabilize and reactivate the native NHases.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.667-673
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• 2009

This study has carried out to evaluate the performance of single (electrolysis, UV and ultrasonic process) and complex process (Electrolysis+UV, UV+Ultrasonic and Electrolysis+Ultrasonic) for the purpose of disinfection of Escherichia coli in water. The order of disinfection performance for E. coli in single process lie in: Electrolysis ${\fallingdotseq}$ UV >> ultrasonic process. OH radical was not produced in single disinfection process. Among the three kinds of complex process, disinfection performance of the Electrolysis+UV was higher than that of the other process (UV+Ultrasonic and Electrolysis+Ultrasonic). It demonstrated a synergetic effect between the UV and electrolysis. When the use of $Na_2SO_4$ as electrolyte instead of NaCl, current increase or more reaction time was needed for the complete disinfection. The disinfection performance of pre-electrolysis (20 W, 30sec) and post-UV (10 W, 30 sec) was higher than that of the simultaneous electrolysis+UV process at same electric power (30 W, 30 second).

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.8
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• pp.1195-1199
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• 2011

Inactivation of foodborne pathogenic bacteria in corn silk tea was evaluated using a microwave plasma sterilization system (MPSS). Corn silk tea was inoculated with Escherichia coli and Listeria monocytogenes, treated with an MPSS treatment, and stored at 25$^{\circ}C$ for 12 days. The one, two, and three cycles of treatment with MPSS reduced the population of E. coli by 1.14, 2.49, and 5.72 log CFU/mL, respectively, compared to that of the control. In the case of L. monocytogenes, one, two, and three cycles of MPSS treatment reduced the population by 1.93, 4.49, and 6.62 log CFU/mL, respectively. Both E. coli and L. monocytogenes were eliminated within four cycles of treatment with MPSS, and even after 12 days of storage, the bacteria were not detected. Total polyphenol content in the corn silk tea did not change much among treatments, and turbidity of the corn silk tea improved following four cycles of MPSS treatment. These results suggest that MPSS treatment can be useful for improving the microbial safety and quality of corn silk tea during storage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.10
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• pp.67-75
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• 2011

Although membrane technologies are widely applied to the water and wastewater treatment processes, strategy for the control of membrane biofouling is strongly required. In this study, a possibility of control of membrane biofouling using HVI(High Voltage Impulse) was verified based on the inactivation of microorganisms by the HVI. The HVI system was consisted of power supply, voltage amplifier, impulse generator and disinfection chamber and the model microorganism was E. coli. When 15[kV/cm] of electric fields was applied to the E. coli solution, inactivation of the microorganism was found. A possibility of the control of membrane biofouling using HVI was verified with experiments of membrane filtration with and without exposure of the HVI to biomass solution. Another membrane filtration experiments with the contaminated membranes by E. coli solution were carried out and indicate that the HVI could be used as an alternative method for membrane biofouling control. A series of simulation of the electric fields between electrodes and microorganisms was carried out for the visualization of the disinfection that showed where the electric fields are formed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.9
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• pp.1-5
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• 2009

Disinfection using UV irradiation has been considered to an alternative for chlorination because it does not suffer from disinfection byproducts problem. The aim of this study was to verify if UV irradiation with 368.6[nm] wavelength has a potential to be used a efficient disinfection. UV irradiation was given for 60 minutes to E. coli. which was used as a model microorganism. Remarkable decrease in number of microorganism was not observed for initial 30 minutes, however, 83.3[%] of disinfection efficiency was achieved after 30 minutes of irradiation. Inactivation constant, k was determined to 0.00868[$cm^2$]/([$mW{\cdot}s$]) using kinetic approach.

• Food Science and Preservation
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• v.16 no.5
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• pp.636-643
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• 2009

Inactivation by UV-C irradiation of Escherichia coli O157:H7 and Listeria monocytogenes inoculated onto washed carrots was examined. Carrot samples were inoculated with 6-7 log CFU/mL of E. coli O157:H7 or L. monocytogenes, treated with doses of 0, 1, 3, 5, or $10\;kJ/m^2$ UV-C, and stored at $4{\pm}1^{\circ}C$ for 8 d. The populations of E. coli O157:H7 and L. monocytogenes significantly decreased with increasing irradiation dose (p<0.05). In particular, E. coli O157:H7 and L. monocytogenes populations fell significantly by 2.35 and 2.38 log CFU/g at $10\;kJ/m^2$, respectively, compared to control values. UV-C irradiation inhibited color changes and decreased the whiteness index in carrot during storage, compared to controls. Sensory evaluation results showed that UV-C-treated carrots had better sensory characteristics than did the control. Therefore, the results suggest that UV-C irradiation could be useful to improve the microbial safety and sensory qualities of fresh-cut carrots during storage.

• KSBB Journal
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• v.19 no.4
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• pp.331-334
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• 2004

In vivo characterization of FadB homologous enzymes including PaaG, YdbU and YgfG for medium-chain-length (MCL) polyhydroxyalkanoate (PHA) biosynthesis was carried out in fadB mutant Escherichia coli. Previously, it was reported that amplification of FadB homologous enzymes such as PaaG and YdbU in fadB mutant E. coli resulted in enhanced biosynthesis of MCL-PHA by greater than two fold compared with control strain. In this study, we constructed paaG fadB double mutant E. coli WB114 and ydbU fadB double mutant E. coli WB115 to investigate the roles of PaaG and YdbU in biosynthesis of MCL-PHA. Inactivation of paaG and ydbU genes in fadB mutant E. coli harboring Pseudomonas sp. 61-3 phaC2 gene reduced the MCL-PHA production to 0.16 and 0.16 PHA g/L, respectively from 2 g/L of sodium decanoate, which are much lower than 0.43 PHA g/L obtained with fadB mutant E. coli WB101 harboring the phaC2 gene. Also, we identified new FadB homologous enzyme YgfG, and examined its roles by overexpression of ygfG and construction of ygfG fadB double mutant E. coli WB113.

• Food Science of Animal Resources
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• v.32 no.1
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• pp.1-5
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• 2012

The objective of this study was to examine the effects of a combined treatment regarding antimicrobial food ingredients and high pressure processing (HP) on the inactivation efficiency of Escherichia coli and Listeria monocytogenes inoculated into ground pork. Ethanol extracted from garlic, leeks, onions, and ginger powder was prepared. Half of the prepared powder was irradiated at 5 kGy to see the effect of pasteurization before addition. The prepared food ingredients were added into radiation-sterilized ground pork (1%, w/w), and inoculated with E. coli and L. monocytogenes. The samples were vacuum-packed and applied with HP at 0.1 (control), 300, 450, and 600 MPa. Microbial log reduction increased with the increase of pressure up to 600 MPa. With minor exceptions, overall efficiency of HP treatment with regards to inactivation of pathogens increased. Inoculated microorganisms showed approximately 7-8 Log reductions by 600 MPa, except for L. monocytogenes treated with garlic (5.7 Log reductions). The E. coli reduction in ground pork mixed with ethanol extracted garlic showed the highest efficiency (1.86) compared to leeks (1.25-1.31), onions (1.17-1.44), and ginger (1.50-1.82) when treated at an HP of 450 MPa. There was no evidence for the advantage of pasteurization concerning the food ingredients before addition of antimicrobial food ingredients and HP. Results demonstrate that the combination of antimicrobial food ingredients and HP treatment may help improve the efficiency of sterilization in meat systems.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.136-141
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• 2009

Inactivation rates between enterococci and total coliforms were compared in order to find the suitability of enterococci as an indicator microorganism under various experiment conditions - freshwater and/or seawater, indoor and/or outdoor conditions. In case of indoor laboratory experiments, inactivation rates of enterococci ($k_D$: 0.050~0.082) were faster than those of total coliforms ($k_D$: 0.034~0.045) in freshwater matrix. In seawater matrix, however, survival rate of enterococci was longer than that of total coliforms at two out of three experiments in indoor condition. When incubated in outdoor conditions, enterococci were inactivated significantly more rapidly than total coliforms both in freshwater and seawater matrices. With these results, enterococci appear to be less suitable than total coliforms in terms of inactivation rates.