• Journal of Microbiology and Biotechnology
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• 제22권10호
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• pp.1395-1400
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• 2012

In this study, we investigated various cultural and operational factors to enhance electricity generation in a microbial fuel cell (MFC) using Geobacter sulfurreducens. The pure culture of G. sulfurreducens was cultivated using various substrates including acetate, malate, succinate, and butyrate, with fumarate as an electron acceptor. Cell growth was observed only in acetate-fed medium, when the cell concentrations increased 4-fold for 3 days. A high acetate concentration suppressed electricity generation. As the acetate concentration was increased from 5 to 20 mM, the power density dropped from 16 to $13mW/m^2$, whereas the coulombic efficiency (CE) declined by about half. The immobilization of G. sulfurreducens on the anode considerably reduced the enrichment period from 15 to 7 days. Using argon gas to create an anaerobic condition in the anode chamber led to increased pH, and electricity generation subsequently dropped. When the plain carbon paper cathode was replaced by Pt-coated carbon paper (0.5 mg $Pt/cm^2$), the CE increased greatly from 39% to 83%.

• 한국미생물·생명공학회지
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• 제48권4호
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• pp.491-505
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• 2020

A newly isolated strain, Proteus vulgaris OR34, from olive mill waste was found to secrete an alkaline extracellular lipase at 11 U·ml-1 when cultivated on an optimized liquid medium. This lipase was purified 94.64-fold with a total yield of 9.11% and its maximal specific activity was shown to be 3232.58 and 1777.92 U·mg-1 when evaluated using the pH-stat technique at 55℃ and pH 9 and Tributyrin TC4 or olive oil as the substrate. The molecular mass of the pure OR34 lipase was estimated to be around 31 kDa, as revealed by SDS-PAGE and its substrate specificity was investigated using a variety of triglycerides. This assay revealed that OR34 lipase preferred short and medium chain fatty acids. In addition, this lipase was stable in the presence of high concentrations of bile salt (NaDC) and calcium ions appear not to be necessary for its activity. This lipase was inhibited by THL (Orlistat) which confirmed its identity as a serine enzyme. In addition, the immobilization of OR34 lipase by adsorption onto calcium carbonate increased its stability at higher temperatures and within a larger pH range. The immobilized lipase exhibited a high tolerance to organic solvents and retained 60% of its activity after 10 months of storage at 4℃. Finally, the OR34 lipase was applied in biodiesel synthesis via oleic acid mediated esterification of methanol when using hexane as solvent. The best conversion yield (67%) was obtained at 12 h and 40℃ using the immobilized enzyme and this enzyme could be reused for six cycles with the same efficiency.

• 공업화학
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• 제10권6호
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• pp.852-856
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• 1999

산업폐수중의 질소 인 제거에 유용한 미생물을 고정화할 수 있는 담체의 제조를 목적으로 하여, 양 말단이 methacryl기로 치환된 poly(ethyleneglycol)(PEG) 및 Poly(tetramethylene glycol)(PTMG)을 합성하였다. 합성된 프레폴리머와 UV조사하에서 가교한 하이드로겔의 구조는 $^1H$-NMR, FT-IR 분광기로 확인하였다. 프레폴리머 사슬의 길이(M.W. 1,000~8,000) 또는 PEG/PTMG의 혼합비를 달리하면서 광경화된 하이드로겔을 제조하였다. 광경화물의 친수성, 함수율, 기계적 강도 등과 같은 광경화 특성 및 pore size 등을 조사한 결과, 분자량 1000인 PEG 및 PEG(MW1000)와 PTMG (MW2900)를 7:3의 비율로 제조한 하이드로겔에서 최적의 결과를 나타내었다.

• KSBB Journal
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• 제17권3호
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• pp.213-227
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• 2002

To date, the majority of biosensor technologies use binding components such as enzymes antibodies, nucleic acids and protein ligands. In contrast, the goal underlying the use of cells and tissues of animals and plants for a sensor system is to obtain systems capable of extracting information based on the biological activity, mechanisms of action and consequences of exposure to a chemical or biological agent of interest. These systems enable the interrogation of more complex biological response and offer the potential to gather higher information content from measuring physiologic and metabolic response. In these articles, same of the recent trends and applications of microbial biosensors in environmental monitoring and for use in food and fermentations have been reviewed. This endeavor presents many technological challenges to fabricate new microbial biosensors for other scientific field.

• Journal of Microbiology
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• 제44권3호
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• pp.354-359
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• 2006

This study examined the capacity of immobilized bacteria to degrade petroleum hydrocarbons. A mixture of hydrocarbon-degrading bacterial strains was immobilized in alginate and incubated in crude oil-contaminated artificial seawater (ASW). Analysis of hydrocarbon residues following a 30-day incubation period demonstrated that the biodegradation capacity of the microorganisms was not compromised by the immobilization. Removal of n-alkanes was similar in immobilized cells and control cells. To test reusability, the immobilized bacteria were incubated for sequential increments of 30 days. No decline in biodegradation capacity of the immobilized consortium of bacterial cells was noted over its repeated use. We conclude that immobilized hydrocarbon-degrading bacteria represent a promising application in the bioremediation of hydrocarbon-contaminated areas.

• Journal of Microbiology and Biotechnology
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• 제24권5호
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• pp.639-647
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• 2014

Laccases have a broad range of industrial applications. In this study, we immobilized laccase on $SiO_2$ nanoparticles to overcome problems associated with stability and reusability of the free enzyme. Among different reagents used to functionally activate the nanoparticles, glutaraldehyde was found to be the most effective for immobilization. Optimization of the immobilization pH, temperature, enzyme loading, and incubation period led to a maximum immobilization yield of 75.8% and an immobilization efficiency of 92.9%. The optimum pH and temperature for immobilized laccase were 3.5 and $45^{\circ}C$, respectively, which differed from the values of pH 3.0 and $40^{\circ}C$ obtained for the free enzyme. Immobilized laccase retained high residual activities over a broad range of pH and temperature. The kinetic parameter $V_{max}$ was slightly reduced from 1,890 to 1,630 ${\mu}mol/min/mg$ protein, and $K_m$ was increased from 29.3 to 45.6. The thermal stability of immobilized laccase was significantly higher than that of the free enzyme, with a half-life 11- and 18-fold higher at temperatures of $50^{\circ}C$ and $60^{\circ}C$, respectively. In addition, residual activity was 82.6% after 10 cycles of use. Thus, laccase immobilized on $SiO_2$ nanoparticles functionally activated with glutaraldehyde has broad pH and temperature ranges, thermostability, and high reusability compared with the free enzyme. It constitutes a notably efficient system for biotechnological applications.

• 센서학회지
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• 제23권1호
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• pp.35-41
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• 2014

Microbes have been used extensively in various fields of researches and industries but has not been used widely for microfluidic biosensor applications because it is difficult to immobilize properly to a small space. Therefore, we developed a microbial immobilization method for microfluidic devices using single-walled nanotubes and dielectrophoretic force. Single-walled nanotubes and Escherichia coli were aligned between two cantilever electrodes by a positive dielectrophoretic force resulting in a film of single-walled nanotubes with attached Escherichia coli. The optimal condition of film formation without a cell lysis was investigated. Diameter of single-walled nanotubes and electric field (intensity and duration of application) had an effect on the cell viability. On the other hand, the cell concentration of the suspension did not affect the cell viability. Paraoxon was detected using single-walled nanotubes film with attached Escherichia coli that expressed organophosphorus hydrolase. This film which is suspended from the substrate showed faster response time than sensors that are not suspended from the substrate.

• 한국식품과학회지
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• 제30권5호
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• pp.1222-1228
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• 1998

스트레스에 의해서 생체는 에너지 대사를 증가시키며, 에너지 대사의 증가는 높은 반응성의 ROS를 생성한다. ROS는 높은 반응성으로 인해 지질, 단백질 등을 과산화시켜 원래의 활성을 잃게함으로 이런 ROS에 대해서 높은 소거능을 지니고 흡수가 쉬운 SOD 유사물질의 투여가 스트레스로 인한 생체내 산화적 손상을 억제할 수 있을 것으로 생각된다. 이것을 확인하기위해서 실험용 흰 쥐에게 4주간의 고정화 스트레스를 가한 결과, 체중 증가량을 감소시켰으며 스트레스 호르몬의 하나인 5-HIAA의 수준을 증가시켰다. 시험관에서 높은 항산화력을 확인한 루이보스티 추출액을 스트레스를 받은 흰 쥐에게 투여한 결과는 체중 증가량 감소는 완화시켰으나 5-HIAA의 수준을 변화시키지 못하여 스트레스 반응 자체를 억제하지 않는 것으로 판명되었다. 루이보스티의 투여는 스트레스로 인해서 유도되는 뇌 조직의 지질과산화와 단백질 산화를 억제하였으나 SOD, GPx 등의 대표적 항산화 효소 활성의 변화를 유발하지 않았다. 따라서, 루이보스티는 스트레스 반응 자체보다는 그에 따른 2차적 독성 대사산물에 대해서 효소 활성의 증가가 아닌 루이보스티 추출액의 구성분 자체가 세포를 보호한 것으로 생각되며, 루이보스티의 추출액이 열수하에서 추출된 것이기 때문에 지질과산화에 대해서보다 단백질 과산화에 대해 더 높은 보호 활성이 나타난 것으로 생각된다.

• Journal of Microbiology and Biotechnology
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• 제22권6호
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• pp.818-825
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• 2012

Keratinases are exciting keratin-degrading enzymes; however, there have been relatively few studies on their immobilization. A keratinolytic protease from Chryseobacterium sp. kr6 was purified and its partial sequence determined using mass spectrometry. No significant homology to other microbial peptides in the NCBI database was observed. Certain parameters for immobilization of the purified keratinase on chitosan beads were investigated. The production of the chitosan beads was optimized using factorial design and surface response techniques. The optimum chitosan bead production for protease immobilization was a 20 g/l chitosan solution in acetic acid [1.5% (v/v)], glutaraldehyde ranging from 34 g to 56 g/l, and an activation time between 6 and 10 h. Under these conditions, above 80% of the enzyme was immobilized on the support. The behavior of the keratinase loading on the chitosan beads surface was well described using the Langmuir model. The maximum capacity of the support ($q_m$) and dissociation constant ($K_d$) were estimated as 58.8 U/g and 0.245 U/ml, respectively. The thermal stability of the immobilized enzyme was also improved around 2-fold, when compared with that of the free enzyme, after 30 min at $65^{\circ}C$. In addition, the activity of the immobilized enzyme remained at 63.4% after it was reused five times. Thus, the immobilized enzyme exhibited an improved thermal stability and remained active after several uses.

• 한국식품과학회지
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• 제16권3호
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• pp.267-272
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• 1984

미생물 세포를 효소 고정화 담체로 사용하여 ${\beta}-fructofuranosidase$를 고정화 시켰다. Penicillium spp. "K-8"로 명명된 곰팡이를 배양한 뒤 균체의 세포벽에 존재하는 다당체를 periodate와 반응시켜 활성화된 알데히드기를 얻을 수 있었다. 이 때 건조 세포 g당 periodate, 1.2g이 최적 농도이었고, 이 농도하에서 온도가 알데히드 형성에 미치는 영향은 거의 없었다. 활성화된 균체에 ${\beta}-fructofuranosidase$를 공유결합에 의하여 고정화시켰다. 더 높은 효소의 고정화를 위하여 이를 glutaraldehyde를 처리한 바 0.5%의 농도와 1시간의 반응조건에서 최대 효소 고정화율 26%를 나타내었다. 이 조건에 의해 제조한 고정화 효소는 kinetic parameters로서 최적온도가 $55^{\circ}C$, 최적 pH가 5, Km값이 55mM. Ea가 19kJ $mol^{-1}$이었다. 회분식 반응조내에서는 6번의 반복된 반응기간동안 고정화 효소 활성에 약간의 감소가 있었으나 비교적 좋은 역가의 안정성을 보여주었다.