• Journal of Microbiology and Biotechnology
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• v.24 no.7
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• pp.879-887
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• 2014

Bacteria that mediate the anaerobic oxidation of ammonium (anammox) have been detected in natural ecosystems, as well as various wastewater treatment systems. In this study, sludge from a particular landfill leachate anaerobic treatment system was selected as the incubation seed for anammox microorganism enrichment owing to its possible anammox activity. Transmission electron microscopy observation, denaturing gradient gel electrophoresis analysis, and cloning/sequencing techniques were applied to identify the diversity of anammox microorganisms throughout the incubation. During the early stage of operation, the diversity of anammox microorganisms was similar to the original complex microbes in the seed sludge. However, as incubation time increased, the anammox microorganism diversity within the system that was originally dominated by Candidatus (Ca.) Brocadia sp. was replaced by Ca. Anammoxoglobus propionicus. The domination of Ca. Anammoxoglobus propionicus produced a stable removal of ammonia (70 mg-N/l) and nitrite (90 mg-N/l), and the total nitrogen removal efficiency was maintained at nearly 95%. The fluorescence in situ hybridization results showed that Ca. Anammoxoglobus propionicus was successfully enriched from $1.8{\pm}0.6%$ initially to $65{\pm}5%$ after 481 days of operation. Therefore, the present results demonstrated the feasibility of enriching Ca. Anammoxoglobus propionicus from leachate sludge, even though the original cell count was extremely low. Application of this seldom found anammox organism could offer an alternative to current ammonia-nitrogen treatment.

• Journal of Microbiology and Biotechnology
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• v.24 no.1
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• pp.97-105
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• 2014

Quorum quenching (QQ) with a microbial vessel has recently been reported as an economically feasible biofouling control platform in a membrane bioreactor (MBR) for wastewater treatment. In this study, a quorum quenching MBR with a ceramic microbial vessel (CMV) was designed to overcome the extremely low F/M ratio inside a microbial vessel. The CMV was prepared with a monolithic ceramic microporous membrane and AHL-degrading QQ bacteria, Pseudomonas sp. 1A1. The "inner flow feeding mode" was introduced, under which fresh feed was supplied to the MBR only through the center lumen in the CMV. The inner flow feeding mode facilitated nutrient transport to QQ bacteria in the CMV and thus enabled relatively long-term maintenance of cell viability. The quorum quenching effect of the CMV on controlling membrane biofouling in the MBR was more pronounced with the inner flow feeding mode, which was identified by the slower increase in the transmembrane pressure as well as by the visual observation of a biocake that formed on the used membrane surface. In the QQ MBR with the CMV, the concentrations of extracellular polymeric substances were substantially decreased in the biocake on the membrane surface compared with those in the conventional MBR. The CMV also showed its potential with effective biofouling control over long-term operation of the QQ MBR.

• Journal of Microbiology and Biotechnology
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• v.24 no.1
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• pp.87-96
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• 2014

In the present study, a yeast species isolated from CETP, Vellore, Tamilnadu was identified as Cryptococcus sp. VITGBN2 based on molecular techniques and was found to be a potent producer of acidic diacetate sophorolipid in mineral salt media containing vegetable oil as additional carbon source. The chemical structure of the purified biosurfactant was identified as acidic diacetate sophorolipid through GC-MS analysis. This sophorolipid was used as a stabilizer for synthesis of zinc oxide nanoparticles (ZON). The formation of biofunctionalized ZON was characterized using UV-visible spectroscopy, XRD, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The antimicrobial activities of naked ZON and sophorolipid functionalized ZON were tested based on the diameter of inhibition zone in agar well diffusion assay, microbial growth rate determination, protein leakage analysis, and lactate dehydrogenase assay. Bacterial pathogen Salmonella enterica and fungal pathogen Candida albicans showed more sensitivity to sophorolipid biofunctionalized ZON compared with naked ZON. Among the two pathogens, S. enterica showed higher sensitivity towards sophorolipid biofunctionalized ZON. SEM analysis showed that cell damage occurred through cell elongation in the case of S. enterica, whereas cell rupture was found to occur predominantly in the case of C. albicans. This is the first report on the dual role of yeast-mediated sophorolipid used as a biostabilizer for ZON synthesis as well as a novel functionalizing agent showing antimicrobial property.

• Journal of Microbiology and Biotechnology
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• v.23 no.3
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• pp.364-374
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• 2013

Monacolin K and yellow pigment, produced by Monascus sp., have each been proven to be beneficial compounds as antihypercholesterolemic and anti-inflammation agents, respectively. However, citrinin, a human toxic substance, was also synthesized in this fungus. In this research, solidstate fermentation of M. purpureus TISTR 3541 was optimized by statistical methodology to obtain a high production of monacolin K and yellow pigment along with a low level of citrinin. Fractional factorial design was applied in this study to identify the significant factors. Among the 13 variables, five parameters (i.e., glycerol, methionine, sodium nitrate, cultivation time, and temperature) influencing monacolin K, yellow pigment, and citrinin production were identified. A central composite design was further employed to investigate the optimum level of these five factors. The maximum production of monacolin K and yellow pigment of 5,900 mg/kg and 1,700 units/g, respectively, and the minimum citrinin concentration of 0.26 mg/kg were achieved in the medium containing 2% glycerol, 0.14% methionine, and 0.01% sodium nitrate at $25^{\circ}C$ for 16 days of cultivation. The yields of monacolin K and yellow pigment were about 3 and 1.5 times higher than the basal medium, respectively, whereas citrinin was dramatically reduced by 36 times.

• Journal of Microbiology and Biotechnology
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• v.26 no.11
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• pp.1933-1942
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• 2016

A novel ${\alpha}-glucoside$ hydrolase (named PspAG97A) from glycoside hydrolase family 97 (GH97) was cloned from the deep-sea bacterium Pseudoalteromonas sp. K8, which was screened from the sediment of Kongsfjorden. Sequence analysis showed that PspAG97A belonged to GH97, and shared 41% sequence identity with the characterized ${\alpha}-glucoside$ BtGH97a. PspAG97A possessed three key catalytically related glutamate residues. Mutation of the glutamate residues indicated that PspAG97A belonged to the inverting subfamily of GH97. PspAG97A showed significant reversibility against changes in salt concentration. It exhibited halophilic ability and improved thermostability in NaCl solution, with maximal activity at 1.0 M NaCl/KCl, and retained more than 80% activity at NaCl concentrations ranging from 0.8 to 2.0 M for over 50 h. Furthermore, PspAG97A hydrolyzed not only ${\alpha}-1,4-glucosidic$ linkage, but also ${\alpha}-1,6-$ and ${\alpha}-1,2-glucosidic$ linkages. Interestingly, PspAG97A possessed high catalytic efficiency for long-chain substrates with ${\alpha}-1,6-linkage$. These characteristics are clearly different from other known ${\alpha}-glucoside$ hydrolases in GH97, implying that PspAG97A is a unique ${\alpha}-glucoside$ hydrolase of GH97.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.5
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• pp.288-292
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• 2007

Seafood, if eaten raw, carries the risk of food poisoning. Seafood poisoning is often caused by pathogenic microorganisms originating from fecal contamination, such as Salmonella sp. and norovirus. Fecal coliforms are an important indicator of fecal contamination. Therefore, data on fecal coliforms are very important for evaluating the safety of fisheries in coastal areas. In this study, 2,226 sea water samples were collected from the southeast coast of Korea, and total and fecal coliforms were compared and analyzed. Total coliforms were detected in 76.5% of the samples and 71.4% of the total coliforms were fecal coliforms. At sea water temperatures above $20.0^{\circ}C$, total coliforms were found in 78.8% of the samples and fecal coliforms constituted 72.0% of the total coliforms. In sea water below $19.9^{\circ}C$, the respective values were 74.6% and 70.9%. These results suggest that temperature does not have a significant effect on the detection of fecal coliforms. When the salinity exceeded 30.0%o, total coliforms were found in 72.1% of the samples and fecal coliforms constituted 66.0% of these. At salinities below 29.9%o, the respective values for total and fecal coliforms were 90.4% and 85.2%. These results strongly suggest that the detection of fecal coliforms is proportional to the amount of precipitation.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.156-156
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• 2016

The effect of nitrogen doping on the mechanical and tribological performance of single-layer tetrahedral amorphous carbon (ta-C:N) coatings of up to $1{\mu}m$ in thickness was investigated using a custom-made filtered cathode vacuum arc (FCVA). The results obtained revealed that the hardness of the coatings decreased from $65{\pm}4.8GPa$ to $25{\pm}2.4GPa$ with increasing nitrogen gas ratio, which indicates that nitrogen doping occurs through substitution in the $sp^2$ phase. Subsequent AES analysis showed that the N/C ratio in the ta-C:N thick-film coatings ranged from 0.03 to 0.29 and increased with the nitrogen flow rate. Variation in the G-peak positions and I(D)/I(G) ratio exhibit a similar trend. It is concluded from these results that micron-thick ta-C:N films have the potential to be used in a wide range of functional coating applications in electronics. To achieve highly conductive and wear-resistant coatings in system components, the friction and wear performances of the coating were investigated. The tribological behavior of the coating was investigated by sliding an SUJ2 ball over the coating in a ball-on-disk tribo-meter. The experimental results revealed that doping using a high nitrogen gas flow rate improved the wear resistance of the coating, while a low flow rate of 0-10 sccm increased the coefficient of friction (CoF) and wear rate through the generation of hematite (${\alpha}-Fe_2O_3$) phases by tribo-chemical reaction. However, the CoF and wear rate dramatically decreased when the nitrogen flow rate was increased to 30-40 sccm, due to the nitrogen inducing phase transformation that produced a graphite-like structure in the coating. The widths of the wear track and wear scar were also observed to decrease with increasing nitrogen flow rate. Moreover, the G-peaks of the wear scar around the SUJ2 ball on the worn surface increased with increasing nitrogen doping.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.2
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• pp.1-10
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• 2003

This paper presents an efficient method for image segmentation based on a multiresolution application of a wavelet transform and watershed segmentation algorithm. The procedure toward complete segmentation consists of four steps: pyramid representation, image segmentation, region merging and region projection. First, pyramid representation creates multiresolution images using a wavelet transform. Second, image segmentation segments the lowest-resolution image of the pyramid using a watershed segmentation algorithm. Third, region merging merges the segmented regions using the third-order moment values of the wavelet coefficients. Finally, the segmented low-resolution image with label is projected into a full-resolution image (original image) by inverse wavelet transform. Experimental results of the presented method can be applied to the segmentation of noise or degraded images as well as reduce over-segmentation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.2
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• pp.1-10
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• 2004

This paper proposes the method that design CLUT(color look-up table) simultaneously processing gamut mapping and color space conversion using only CLUT without complex computation. After CLUT is constructed using scanner gamut and printer gamut, the scanner gamut is extended to include original scanner gamut. This extended scanner gamut is used as input CIE $L^{*}$ $a^{*}$ $b^{*}$ values for CLUT. Then CMY values are computed by using gamut mapping. Input RGB image of scanner is converted into CIE $L^{*}$ $a^{*}$ $b^{*}$ by using regression function. CIE $L^{*}$ $a^{*}$ $b^{*}$ values of scanner are converted into CMY values without computation of additional gamut mapping using the proposed CLUT. In the experiments, the proposed method resulted in the similar color difference, but reduced the complexity computation than the direct computing method to process gamut mapping and color space conversion respectively.espectively.ively.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.3
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• pp.1-10
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• 2000

This paper proposes a novel video coding system with rate control based on fractal algorithm To overcome the demerits of excessive amounts of coded bit generated by previous fractal coding methodology. the proposed system classifies the Image into three classes such as background, motion compensation, and fractal coding area. The motion vector for motion compensation, and the fractal offset value that is difference value between the predicted offset and the least-square approximated value are coded with variable length code The decision method which determines threshold value of partitioning quadtree is applied to the bit-rate control algorithm considering the quantity of currently generated bits and fixed channel bandwidth Experimental result shows that the proposed system enhances compression ratio 1.8 times higher than previous method for the same image quality, and performs efficient rate control for fixed channel bandwidth.