• Korean Journal of Microbiology
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• v.50 no.4
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• pp.308-312
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• 2014

In this study, we conducted a next generation sequencing based microbial community analysis to investigate gut microbiota of the two commercially most available swine breeds, Yorkshire and Landrace. Bacterial 16S rRNA gene was amplified from fecal DNA using universal primer sets designed for V4 regions. Our comparison analysis of the gut microbiota of the two breeds suggested that their gut microbiota changed depending on the growth stages, while the difference between the two breeds was insignificant. However, there was a limited number of genera, the abundance of which was found to be different between the breeds. Those included the genus Xylanibacter in the Yorkshire samples, which was previously reported as a fiber digesting bacteria, likely increasing energy harvesting capacity of swine. In addition, others included opportunistic pathogens mostly found in the Yorkshire samples while the Landrace samples had significantly more prevalent Clostridium_IV species that were known to play a key role in systemic immunity of hosts. While microbial community shifts was found to be associated with growth stages, the difference between the two breeds seemed to be insignificant. However, there were several bacterial genera showing differential abundance, which may affect growth of hosts.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.427-434
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• 2015

Most of halophilic archaea are found in the various hypersaline environments including solar saltern, salt lake with very high salt concentration. The present study is about isolation and characterization of halphilic archaea from Gomso solar saltern known as a representative high salt environment in Korea. In order to isolate the halophilic archaea, we prepared and used high salt medium. Finally, total 7 strains obtained were tentatively identified based on comparative similarity analysis for 16S rRNA gene sequence and physiological traits. All halophilic archaea belonged to Haloruburm, Halogeometriucm, Halobacterium, and Haloarcula genera. These isolates were all Gram-staining negative, and growth was not observed using nitrate as an alternative electron acceptor under anaerobic conditions. In addition, all isolates required about 12-30% (w/v, NaCl) salt. This case study might provide basic information on microbial isolation technologies and related research in halophilic microorganisms from domestic halophilic environments, and contribute to obtaining useful indigenous halophilic archaea in a variety of extreme environmental conditions.

• KSBB Journal
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• v.7 no.4
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• pp.308-316
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• 1992

Two-stage continuous culture system has been studied intensively to maximize the productivity of a cloned gene product in unstable recombinant microorganism. As an effort to optimize the two-stage process, transient behavior of the second-stage was studied theoretically as well as experimentally using Escherichia coli Kl2$\delta$Hl$\delta$trp. A mathematical model describing the transient response to a step change in dilution rate was developed based on the assumption that the adaptation rate of cell growth is proportional to the available growth potential, which is defined as the difference in dilution rates between before and after shift-up. The kinetic parameters appearing in the model equations were the dimensionless step increase in growth rate($\alpha$) and the adaptation rate constant(k). These parameters were evaluated for various dilution rates and temperatures by washout method. This relatively simple adaptation model could predict the specific growth rate of the second-stage successfully. Advantage and disadvantage of the proposed model are also discussed.

• KSBB Journal
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• v.18 no.6
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• pp.443-447
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• 2003

The microorganism was isolated from the night soil treatment plant for the removal of sulfur compounds. The growth conditions of the sulfur-oxidizing bacteria were investigated and the isolate characterized as Thiobacillus noveilus SRM. The optimal pH of Thiobacillus novellus SRM on cell growth was pH 7.0 and the optimal temperature was 30$^{\circ}C$ and the optimal air flow rate was 1 vvm, respectively. As a results of cell growth from the Monod plot, the specific growth rate was 0.032 hr$\^$-l/, $V_{max}$ was 1.43 hr$\^$-l/ and $K_{m}$ was 0.32, respectively. The thiosulfate oxidation by Thiobacillus novellus SRM was made of sulfate ion. The sulfate ion reduced pH and decreased cell growth.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.3
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• pp.119-126
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• 2001

A process for the production of bioplastics from wastewater with an open microbial culture was developed and evaluated. The process consists of a selection reactor to select bacteria in feast/famine regime and an accumulation reactor to produce PHA using selected bacteria. Polyhydroxyalkanoate(PHAs) accumulating bacteria could be efficiently grown in a sequencing batch reactor(SBR) without any growth limitation. For the high production of PHA limitation such as oxygen and nutrients seemed to be needed. Accumulation experiments were performed to evaluate the level of accumulation of PHA. Limited aeration had no effect, but nutrients limitation showed high accumulation. Bacteria which were selected in the SBR could accumulate PHA till 60% of cellular dry weight in accumulation experiments under nitrogen limitation. PHA accumulation rate decreased with increasing PHA content in the cells. Clearly, PHA accumulation rate has a strong correlation with the PHA content of the cells.

• Journal of Applied Biological Chemistry
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• v.57 no.1
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• pp.83-87
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• 2014

The effects of combined treatment of aqueous chlorine dioxide ($ClO_2$) and fumaric acid on the microbial growth in fresh-cut paprika were investigated. After the combined treatment, the populations of total aerobic bacteria and inoculated Listeria monocytogenes in the paprika sample were reduced by 0.82 and 1.21 log CFU/g, respectively, compared to those of the control. In addition, after 10 d of storage at $10^{\circ}C$, the populations were decreased by 1.21 and 2.10 log CFU/g, respectively. The predictive model for the populations of total aerobic bacteria and L. monocytogenes in the paprika was applied during storage. The prediction equation using Gompertz model was appropriate, based on the statistical analysis such as accuracy factor and bias factor. These results suggest that the combined treatment of aqueous $ClO_2$ and fumaric acid can be an effective technology for microbial decontamination and it can improve microbial safety by decreasing maximum growth rate and increasing lag time of bacteria in the fresh-cut paprika.

• Microbiology and Biotechnology Letters
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• v.44 no.4
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• pp.488-492
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• 2016

Saccharomycopsis fibuligera is an amylolytic yeast that exhibits raw starch-degrading activity. In this study, adaptive laboratory evolution was performed to improve the tolerance of S. fibuligera to lactic acid by prolonged repeated batch fermentation in which the lactic acid concentration was gradually increased. The evolved S. fibuligera strain exhibited a significantly enhanced tolerance to lactic acid at concentrations up to 2.5% (w/v), as assessed by determining its specific growth rate using a plate assay. Scanning electron microscopy revealed an elongated and perforated morphology of the parent strain under lactic acid stress, indicating that its membrane might be more prone to damage caused by lactic acid than that of the evolved strain.

• Bulletin of Food Technology
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• v.9 no.2
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• pp.111-127
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• 1996

Potassium Sorbate의 향균능력측정결과 효모(Saccharomyces cerevisiae)의 성장에 대하여 uncompetitive 기작으로 작용하였다. 열처리 실험의 결과 Potassium Sorbate는 가열온도에 대하여 Arrhenius, 또한 가열시간에 대하여 1차반응식관계로 향균능력을 잃었으며 따라서 보존제로 Potassium Sorbate를 식품에 첨가후 포장, 가열살균하는 일반 식품가공공정상에서 가열살균공정이 첨가 보존제의 잔류향균능력을 잃게 하는 것으로 나타났다. 플라스틱 film과 치즈안에서 Potassium Sorbate의 확산계수 및 확산에 의한 물질전달 현상을 수학적모델과 컴퓨터 simulation 그리고 실험에 의해 구하였다. 저밀도폴리에틸렌(LDPE)이 범용플라스틱중에서 가장 작은 확산계수를 가져 빠른 물질전달이 요구되는 film층 또는 약물저장층으로 적합한것으로 나타났다. 그외 고밀도 폴리에틸렌(HDPE)과 폴리프로필렌(PP), 폴리에스터(PET)는 느린 물질전달이 요구되는층 또는 복합다층 film에서 물질전달에 단방향성을 주는 고차단층으로 적합한것으로 나타났다. Potassium Sorbate분말과 LDPE resin분말을 섞은후 단일스크루 익스트루더로 항균성 포장 film을 제조한 결과 LDPE film의 tensile strength과 elongation, elastic modulus는 Potassium Sorbate를 3% 이상 포함할때까지 변화하지 않았다. 그러나 film의 투명도는 급격히 낮아졌다. 향균성LDPE film은 효모가 접종된 한천배지상에서 항균물질인 Potassium Sorbate를 배지위로 서서히 방출시켜 효모의 성장속도(growth rate)를 저하시키고 초기성장지체기(lag period)를 연장시킨다. 따라서 식품포장재로 적용시에 미생물의 오염을 막고 식품저장기간을 연장할것이라 여겨진다.

• Resources Recycling
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• v.17 no.2
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• pp.30-35
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• 2008

Mixed acidophilic bacteria were approached for leaching of cobalt and lithium from wastes of lithium ion battery industries. The growth substrates for the mixed mesophilic bacteria are elemental sulfur and ferrous ion. Bioleaching of the metal was due to the protonic action of sulfate ion on the metals present in the waste. It was investigated that bioleaching of cobalt was faster than lithium. Bacterial action could leach out about 80 % of cobalt and 20 % of lithium from the solid wastes within 12 days of the experimental period. Higher solid/liquid ratio was found to be detrimental for bacterial growth due to the toxic nature of the metals. At high elemental sulfur concentration, the sulfur powder was observed to be in undissolved form and hence the leaching rate also decreased with increase of sulfur amount.

• Microbiology and Biotechnology Letters
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• v.30 no.3
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• pp.216-222
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• 2002

To Produce the modified Cheongiu that has high ethanol content, an ethanol-tolerant strain Saccharo-myces cerevislae SE2l1 was screened from Saccharomyces cerevisiae Kyokai No. 10 strain. The isolate showed faster growth than in the medium containing 10% ethanol compared with original strain. The isolate produced a higher concentration of ethanol and showed higher resistance to ethanol, high osmolarity and heat than the original strain. The analyses of yeast membrane components indicated that there were no significant changes in composition of sterols and phospholipids between the isolated and the original strain. However, during the fermentation, the iso-lated strain could change the fatty acid composition in the membrane more rapidly in the direction of decreasing membrane unsaturation and accumulate more trehalose in the cell than the original strain. These data suggest that the ability to change its membrane fatty acid composition and to accumulate trehalose may make the isolated strain easily adapt to changes in external condition.