• Journal of Microbiology and Biotechnology
• /
• v.22 no.4
• /
• pp.547-554
• /
• 2012

Chromium is generated from several industrial processes. It occurs in different oxidation states, but Cr(III) and Cr(VI) are the most common ones. Cr(VI) is a toxic, soluble environmental contaminant. Some bacteria are able to reduce hexavalent chromium to the insoluble and less toxic Cr(III), and thus chromate bioremediation is of considerable interest. An indigenous chromium-reducing bacterial strain, Rb-2, isolated from a tannery water sample, was identified as Ochrobactrum intermedium, on the basis of 16S rRNA gene sequencing. The influence of factors like temperature of incubation, initial concentration of Cr, mobility of bacteria, and different carbon sources were studied to test the ability of the bacterium to reduce Cr(VI) under variable environmental conditions. The ability of the bacterial strain to reduce hexavalent chromium in artificial and industrial sewage water was evaluated. It was observed that the mechanism of resistance to metal was not due to the change in the permeability barrier of the cell membrane, and the enzyme activity was found to be inductive. Intracellular reduction of Cr(VI) was proven by reductase assay using cell-free extract. Scanning electron microscopy revealed chromium precipitates on bacterial cell surfaces, and transmission electron microscopy showed the outer as well as inner distribution of Cr(VI). This bacterial strain can be useful for Cr(VI) detoxification under a wide range of environmental conditions.

• BioChip Journal
• /
• v.12 no.4
• /
• pp.257-267
• /
• 2018

Inertial microfluidics has attracted significant attention in recent years due to its superior benefits of high throughput, precise control, simplicity, and low cost. Many inertial microfluidic applications have been demonstrated for physiological sample processing, clinical diagnostics, and environmental monitoring and cleanup. In this review, we discuss the fundamental mechanisms and principles of inertial migration and Dean flow, which are the basis of inertial microfluidics, and provide basic scaling laws for designing the inertial microfluidic devices. This will allow end-users with diverse backgrounds to more easily take advantage of the inertial microfluidic technologies in a wide range of applications. A variety of recent applications are also classified according to the structure of the microchannel: straight channels and curved channels. Finally, several future perspectives of employing fluid inertia in microfluidic-based cell sorting are discussed. Inertial microfluidics is still expected to be promising in the near future with more novel designs using various shapes of cross section, sheath flows with different viscosities, or technologies that target micron and submicron bioparticles.

• Journal of environmental and Sanitary engineering
• /
• v.15 no.1
• /
• pp.34-38
• /
• 2000

In the screening of phenol-degrading bacteria, a strain showing good growth in media containing phenol was isolated by using enrichment culture from various sample and identified as genus Klebsiella pneumoniae. The optimal temperature and pH for cell growth of Klebsiella pneumoniae was $35^{\circ}C$ and 8.0, respectively. When phenol was added to the minimal media as a sole source of carbon and energy, the concentration of maximum and optimum for cell growth was 1,200ppm and 1,000ppm, respectively. It was observed that Klebsiella pneumoniae was able to degrade 98% of phenol (1,000ppm) after 40hr in culture. The isolated could utilize various kinds of aromatic compounds and showed good growth in presence of phenol, m-cresol and 3-methyl catechol.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.6
• /
• pp.1689-1692
• /
• 2013

Food is a common source of chromium (Cr) exposure. However, it is difficult to analyze Cr in complex food matrices by using inductively coupled plasma mass spectrometry (ICP-MS) because the major isotope, $^{52}Cr$, is masked by interference generated by the sample matrix and the plasma gas. Among the systems available to minimize interference, the recently developed collision-reaction interface (CRI) has a different structure relative to that of other systems (e.g., collision cell technology, octopole reaction system, and dynamic reaction cell) that were designed as a chamber between the skimmer cone and quadrupole. The CRI system introduces collision or reaction gas directly into the plasma region through a modified hole of skimmer cone. We evaluated the use of an CRI ICP-MS system to minimize polyatomic interference of $^{52}Cr$ and $^{53}Cr$ in various foodstuffs. The $^{52}Cr$ concentrations measured in the standard mode were 2-3 times higher than the certified values. This analytical method based on an ICP-MS system equipped with a CRI of helium gas was effective for Cr analysis in complex food matrices.

• Resources Recycling
• /
• v.22 no.3
• /
• pp.28-35
• /
• 2013

The recycling of the Si/SiC mixture sludge obtained from solar cell industry is very significant, environmentally and economically. The sintering characteristics of Si/SiC mixture sludge was studied for the purpose of recycling. In this study, to understand sintering behavior, SiC content in the Si/SiC mixture was controlled using an air separator. Various Si/SiC mixtures having different SiC contents were sintered using carbon black, clay and aluminum hydroxide as sintering aids. Physical properties of Si/SiC mixture and sintered bodies have been characterized using SEM, XRD, particle size analyzer and apparent density measurement. SEM and particle size analysis result confirmed that the fine particles less than 1 ${\mu}m$ decreased or removed more effectively through the air separator in the case of 95% SiC sample compared than the case of 75% SiC sample or original SiC sample. Further, with addition of the Aluminum Hydroxide, ${\beta}$-cristobalite phase gradually decreased while mullite phase gradually increased. The addition of the carbon black improved the sintering characteristics.

• Asian Journal of Atmospheric Environment
• /
• v.7 no.2
• /
• pp.105-113
• /
• 2013

We constructed and tested an airborne peroxyacetyl nitrate (PAN) monitoring system based on luminol chemiluminescence detection with fast gas chromatography. This system allowed for simultaneous measurement of PAN and nitrogen dioxide ($NO_2$) with a time resolution of <2 min. Actual sample masses within the fixed volume sample loop at various altitudes and temperatures were adjusted to standard atmosphere, using measured pressures and temperatures. The airborne PAN measurement system was evaluated during two field studies above the southern Korean Peninsula in August and October 2009. The detection limit based on the ISO approach was 0.035 ppbv PAN, well below the observed concentrations of 0.185-1.49 ppbv during these studies. Under these conditions, the PAN mixing ratios were positively correlated with $O_x$ ($O_x=O_3+NO_2$), with slopes varying between 0.014 and 0.033 and intercepts between 22.6 and 55.1 ppbv $O_x$. The intercepts corresponded roughly to background $O_x$ mixing ratios in central Europe; however, the slopes were above the range of slopes reported in other studies. We also enhanced the durability, safety, and ease of maintenance of the PAN monitoring system by redesigning the structure of the conventional luminol cell.

• Korean Journal of Microbiology
• /
• v.38 no.3
• /
• pp.186-191
• /
• 2002

The usefulness of oligonucleotide DNA chip was evaluated for detection and primary level identification of major waterborne viruses in environmental samples. The enteric waterborne viruses included enterovirus, adenovirus, and rotavirus. Total intracellular RNA of 10 BGM cell plates showing virus-specific cytopathic effects was extracted at the third day after inoculation. The intracellular RNA was then subjected to either enterovirus-specific RT-PCR followed by sequencing analysis, or the DNA chip. Seven out of 10 positive samples in cell culture were positive but the other three sample were turned out to be negative by both RT-PCR and DNA chip analyses. Nucleotide sequencing results and the DNA chip hybridization results of the RT-PCR product were in complete agreement in the identification of the 7 positive samples as enteroviruses. Using the DNA chip, it took only 3∼4 hr to complete detection and primary level identification of target viruses and additional procedures such as gel electrophoresis or nucleotide sequencing were not necessary. We believe that the DNA chip system can be employed as a highly effective and new detection methodology for environmental viruses.

• Korean Journal of Environmental Biology
• /
• v.39 no.1
• /
• pp.32-38
• /
• 2021

Cyanobium is a genus of picoprokaryotic cyanophytes, which includes species worldwide. The present study investigated the morphology, ultrastructure, and molecular phylogeny of the unrecorded genus Cyanobium Rippka & Cohen-Bazire 1983 and species Cyanobium gracile Rippka & Cohen-Bazire 1983. A C. gracile culture from a freshwater sample collected from the Adongji pond was established by single-cell isolation. Morphological data were analyzed using light and transmission electron microscopy. C. gracile lives as solitary cells without gelatinous envelopes and is ovate, oval, or shortly rod-shaped. Thylakoids are laid along the cell walls, with three thylakoid membranes parallel to each other. Nucleoplasm was observed in the center of the cell. Molecular phylogeny performed with data from 16S small subunit ribosomal DNA gene (SSU rDNA) sequences showed that the three strains of C. gracile, including the type strain (PCC6307) and a newly recorded strain (Adong101619), formed a distinct clade with a high supporting value (maximum-likelihood=100, pp=1.00). Based on morphology and molecular data, we report the newly recorded C. gracile in Korea.

• Korean Journal of Ecology and Environment
• /
• v.33 no.2 s.90
• /
• pp.145-151
• /
• 2000

A porous silicate material named as CellCaSi was tested for the removal of microalgae in the water sample from a eutrophic pond. The effects of the CellCaSi on water qualities were investigated on the basis of both the particle size (under 1, 2,and 4 mm) and the added amount (0, 1, 5, and 10 g/l) of the CellCaSi. The removal efficiency of chlorophyll-a was highest at 79% by the addition of 10 g/l of the CellCaSi (under 1 mm) at day 3 after treatment. That is, the removal efficiency of chlorophyll-a by the CellCaSi increased with smaller particle size and more added amount. The dominant species, Chlorella ellipsoidea, was not changed by the addition of the CellCaSi, but the species number and standing crop of the algae diminished. Total nitrogen concentration was not changed much by the addition of the CellCaSi, whereas total phosphorus concentration was reduced. pH and turbidity were not changed by the addition of the CellCaSi, whereas conductivity showed a high correlation with the amount of added CellCaSi ($Y\;=\;29.2 {\cdot}X+306$, $r^2\;=0.984$). Therefore, it seems to be necessary to limit the amount of the CellCaSi under 6.6 g/1 in consideration of a registered maximum conductivity of $500\;{\mu}mhos/cm$ for raw and potable waters.

• Journal of Environmental Science International
• /
• v.13 no.9
• /
• pp.799-806
• /
• 2004

The filtration tests were made in cell with a low concentrated suspension. The suspension with a concentration of $C_{M}$=1.14～2.67$\cdot$$10^{-3}$ g/g consists of paper paint and water. The particles in the suspension have a particle size x<1${\mu}m$. The used depth filters consists of glass fibres, which are coated by polymer. The filtration in depth filters accorded in different mechanism, which were explained by physical models. The model which would be allows to make a promise of the filtration reaction. This filter media allows to get a high filtration time and a good separation rate. The Particle distribution is measured by a photon correlation spectroscopy(PCS). PCS measures particle sizes 0.03 ${\mu}m$${\mu}m$ in the suspension. The filtered suspension has a very low concentration Co{\le}5{\times}10_{-4}$ g/g of solid in sample. The PCS also informs us about the number of the particles in the suspension. The makes it possible to calculate the concentration of the in sample.