• Journal of Microbiology and Biotechnology
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• 제22권3호
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• pp.400-406
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• 2012

To improve the hydrogen yield from biological fermentation of organic wastewater, a co-culture system of dark- and photo-fermentation bacteria was investigated. In a pure-culture system of the dark-fermentation bacterium Clostridium butyricum, a pH of 6.25 was found to be optimal, resulting in a hydrogen production rate of 18.7 ml-$H_2/l/h$. On the other hand, the photosynthetic bacterium Rhodobacter sphaeroides could produce the most hydrogen at 1.81mol-$H_2/mol$-glucose at pH 7.0. The maximum specific growth rate of R. sphaeroides was determined to be 2.93 $h^{-1}$ when acetic acid was used as the carbon source, a result that was significantly higher than that obtained using either glucose or a mixture of volatile fatty acids (VFAs). Acetic acid best supported R. sphaeroides cell growth but not hydrogen production. In the co-culture system with glucose, hydrogen could be steadily produced without any lag phase. There were distinguishable inflection points in a plot of accumulated hydrogen over time, resulting from the dynamic production or consumption of VFAs by the interaction between the dark- and photo-fermentation bacteria. Lastly, the hydrogen production rate of a repeated fed-batch run was 15.9 ml-$H_2/l/h$, which was achievable in a sustainable manner.

• Journal of Microbiology and Biotechnology
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• 제22권5호
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• pp.668-673
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• 2012

Biohydrogen production from organic wastewater by anaerobically activated sludge fermentation has already been extensively investigated, and it is known that hydrogen can be produced by glucose fermentation through three metabolic pathways, including the oxidative decarboxylation of pyruvic acid to acetyl-CoA, oxidation of NADH to $NAD^+$, and acetogenesis by hydrogen-producing acetogens. However, the exact or dominant pathways of hydrogen production in the anaerobically activated sludge fermentation process have not yet been identified. Thus, a continuous stirred-tank reactor (CSTR) was introduced and a specifically acclimated acidogenic fermentative microflora obtained under certain operation conditions. The hydrogen production activity and potential hydrogen-producing pathways in the acidogenic fermentative microflora were then investigated using batch cultures in Erlenmeyer flasks with a working volume of 500 ml. Based on an initial glucose concentration of 10 g/l, pH 6.0, and a biomass of 1.01 g/l of a mixed liquid volatile suspended solid (MLVSS), 247.7 ml of hydrogen was obtained after a 68 h cultivation period at $35{\pm}1^{\circ}C$. Further tests indicated that 69% of the hydrogen was produced from the oxidative decarboxylation of pyruvic acid, whereas the remaining 31% was from the oxidation of NADH to $NAD^+$. There were no hydrogen-producing acetogens or they were unable to work effectively in the anaerobically activated sludge with a hydraulic retention time (HRT) of less than 8 h.

• Journal of Microbiology and Biotechnology
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• 제33권10호
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• pp.1384-1389
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• 2023

This work aimed to evaluate the feasibility of biohydrogen production from Barley Straw and Miscanthus. The primary obstacle in plant biomass decomposition is the recalcitrance of the biomass itself. Plant cell walls consist of cellulose, hemicellulose, and lignin, which make the plant robust to decomposition. However, the hyperthermophilic bacterium, Caldicellulosiruptor bescii, can efficiently utilize lignocellulosic feedstocks (Barley Straw and Miscanthus) for energy production, and C. bescii can now be metabolically engineered or isolated to produce more hydrogen and other biochemicals. In the present study, two strains, C. bescii JWCB001 (wild-type) and JWCB018 (ΔpyrFA Δldh ΔcbeI), were tested for their ability to increase hydrogen production from Barley Straw and Miscanthus. The JWCB018 resulted in a redirection of carbon and electron (carried by NADH) flow from lactate production to acetate and hydrogen production. JWCB018 produced ~54% and 63% more acetate and hydrogen from Barley Straw, respectively than its wild-type counterpart, JWCB001. Also, 25% more hydrogen from Miscanthus was obtained by the JWCB018 strain with 33% more acetate relative to JWCB001. It was supported that the engineered C. bescii, such as the JWCB018, can be a parental strain to get more hydrogen and other biochemicals from various biomass.

• 한국환경보건학회지
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• 제38권2호
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• pp.83-94
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• 2012

The research on microbial fuel cells (MFCs) needs various knowledge of different fields such as electrochemistry, microbiology, environmental engineering, and material engineering. Although electrochemically active bacteria are very diverse, the performance of MFCs is affected primarily by the structure of the reactor system. Thus, the development in the system architecture is critical to lower internal resistance and increase power generation for commercialization. This paper summarizes the principles of MFCs and demonstrates the infinite potential of MFCs in various applications including wastewater treatment, biosensors, biohydrogen production, remote power sources, implantable medical devices, etc.

• Bulletin of the Korean Chemical Society
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• 제31권8호
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• pp.2180-2184
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• 2010

We synthesized and tested the anti-HIV activity of the SATE prodrug of a 2'-methyl 5'-norcarbocyclic adenine analogue. The introduction of a methyl group in the 2'-position was performed by the addition of a carbonyl using isopropenyl magnesium bromide. The adenine base was efficiently coupled using the Mitsunobu reaction. The chemical stability study of the bis(SATE) derivative 18 was measured at neutral (pH 7.2) and slightly acid (milli-Q water, pH 5.5) pH, and compounds 16 and 18 were evaluated as potential anti-HIV-1 agents.

• Journal of Microbiology and Biotechnology
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• 제17권4호
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• pp.668-672
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• 2007

A microcosmal experiment using a metagenomic technique was designed to assess the effect of BTEX (benzene, toluene, ethylbenzene, and xylenes) on an indigenous bacterial community in a Daejeon forest soil. A compositional shift of bacterial groups in an artificial BTEX-contaminated soil was examined by the 16S rDNA PCR-DGGE method. Phylogenetic analysis of 16S rDNAs in the dominant DGGE bands showed that the number of Actinobacteria and Bacillus populations increased. To confirm these observations, we performed PCR to amplify the 23S rDNA and 16S rDNA against the sample metagenome using Actinobacteria-targeting and Bacilli-specific primer sets, respectively. The result further confirmed that a bacterial community containing Actinobacteria and Bacillus was affected by BTEX.

• Bulletin of the Korean Chemical Society
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• 제30권12호
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• pp.2989-2992
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• 2009

An efficient synthetic route of novel 2′(${\alpha}$)-C-fluoro-2′(${\beta}$)-C-methyl carbocyclic nucleoside analogues is described. The key fluorinated intermediate 7 was prepared from the epoxide intermediate 5 via selective ring-opening of epoxide. Coupling of 7 with nucleosidic bases under the Mitsunobu reactions followed by deprotection afforded the target carbocyclic nucleoside analogues. The synthesized compounds were evaluated as inhibitors of the hepatitis C virus (HCV) in Huh-7 cell line in vitro.

• Environmental Engineering Research
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• 제10권1호
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• pp.7-14
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• 2005

The feasibility of hydrogen production with a raw seed sludge through direct acclimation of feedstock was investigated at acidogenic stage, and methane was harvested at followed methanogenic stage in an anaerobic two-stage process. Hydrogen content was higher than 57% at all tested organic loading rates (OLRs) and the yield of hydrogen ranged from 1.5 to 2.4 mol H2/mol hexose consumed and peaked at 6 gVSl-1day-1. Normal butyrate and acetate were main volatile fatty acids (VFAs), whereas the concentration of propionate was insignificant. The hydrogen-producing bacteria, Clostridium thermosaccharolyticum, was detected with strong intensity at all tested organic loading rates (OLRs) by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) analysis. From COD balance in the process, the fraction of the feed-COD converted to the hydrogen-COD at acidogenic stage ranged from 7.9% to 9.3% and peaked at 6 gVSl-1day-1, whereas the fraction of feed-COD converted to the methane-COD at methanogenic stage ranged from 66.2% to 72.3% and peaked at 3 gVSl-1day-1.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.470-473
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• 2006

생물학적 수소생산을 위해 토양으로부터 새로운 균주인 Enterobacter asburiae SNU-1이 분리되었다 이 균주의 경우 다른 균주와는 달리 미생물 생장과 수소생산 phase가 분리되는 특징을 가지고 있다. 이러한 정지기에서의 수소생산은 미생물 내에 존재하는 formate hydrogen lyase를 사응하여 formate 분해에 의해 일어난다. 따라서 본 연구에서는 미생물 생장 phase에서 formate hydrogen lyase가 발현된 미생물을 얻고 이를 formate만 있는 배지에서 수소생산 가능성에 대한 연구를 수행하였다. 앞으로 formate분해를 위한 조건을 최적화한다면 높은 수소생산성을 나타낼 것이라 기대된다. 또한, 이는 formate로부터 미생물촉매를 이용하여 수소를 생산하고 이를 연료전지로 공급하는 생물학적 reformer로써의 이용 가능성을 보여준다.

• KSBB Journal
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• 제20권6호
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• pp.431-437
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• 2005

1. 고온 CSTR은 비교적 짧은 start-up 기간과 높은 $H_2$ 수율을 나타내었다. $H_2$ 생산속도와 $H_2$ 수율의 안정화를 근거로 판단컨대 start-up 기간은 30일 이내이었으며, 최고 $H_2$ 수율은 2.4 mol $H_2/mol$ glucose이었다. 2. 비교적 긴 HRT와 침전조를 이용한 biomass의 재순환에도 불구하고, 유입 포도당의 농도가 낮아 biomass 농도는 다른 중온 반응기에서 보고된 것에 비해 낮은 편이었다. 3. 운전 초기에 $CH_4$이 발생하였으나 8일 이후부터는 pH를 1.0 이하로 유지하였더니 14일 이후로는 거의 검출되지 않는 것으로 봐서 메탄생성균이 식종균에 남아 있더라도 반응기 운전조건을 통해 $CH_4$ 발생을 억제할 수 있었다. 4. 식종 미생물과 반응기로부터 취한 시료의 DGGE band 패튼이 다른 것으로 보아 고온 CSTR 조건에서 식종된 미생물 군집의 조성이 변화하였음을 알 수 있었다. 5. DGGE 분석결과 초기 43일간의 운전기간 동안에 관찰된 미생물 군집조성은 동적인 변화를 나타내었다. 약 14일부터는 biogas 조성이 거의 일정하였으나 미생물 군집은 동적 변화를 나타내었다. F. gondwanens와 T. Thermoanaerobacterium과 계통발생학적으로 가장 연관이 있는 개체군들이 운전 21일과 41일째에 각각 우점으로 나타났다. 6. 본 연구에서 식종 슬러지를 열처리하는데 사용한 조건은 메탄생성균을 완전히 제거하는데 불충분하다는 것은 운전 초기에 $CH_4$이 biogas에서 검출되었고, 식종 슬러지와 반응기로부터 취한 시료에서 메탄생성균이 가지는 mcrA 유전자가 PCR로 증폭되었으므로 알 수 있었다. 7. 메탄생성균의 주요 목에 특이적인 primers를 사용하여 PCR을 실시한 결과 식종슬러지에 있는 메탄생성균들은 주로 Methanosarcinales와 Methanomicrobiales 목에 속하였으며, $CH_4$이 발생했던 때의 반응기에 있는 메탄생성균들은 주로 Methanobacteriales 목에 해당되는 것으로 나타났다.