• Asian-Australasian Journal of Animal Sciences
• /
• v.5 no.3
• /
• pp.511-517
• /
• 1992

Ethanol was utilized by mixed rumen microbes, but addition of pentachlorophenol (25 mg/l), a methanogen inhibitor, suppressed the utilization of ethanol. Carbon monoxide (50% of the gas phase), a hydrogenase inhibitor, more strongly suppressed the utilization of ethanol, propanol, and butanol. These results suggest that the major ethanol utilizers are $H_2$ producers. Ethanol utilization was depressed at low pH (below 6.0). Since methanogens were shown to be relatively resistant to low pH, it appears that ethanol utilizers are particularly sensitive to low pH. Ruminococcus albus and R. flavefaciens in mono-culture produced ethanol from carbohydrate (glucose and cellobiose), even when a high level (170 mM) of ethanol was present. Ethanol was not utilized even in the absence of carbohydrate, but the co-culture of these bacteria with methanogens resulted in the utilization of ethanol, i.e., when $H_2$ was rapidly converted to $CH_4$, R. albus and R. flavefaciens utilized ethanol. These results suggest that ethanol is utilized when the electrons liberated by the oxidation of ethanol are rapidly removed, and ready electron disposal in ethanol-utilizing, $H_2$-producing bacteria is accomplished by the interspecies transfer of $H_2$.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.5
• /
• pp.1115-1119
• /
• 2005

The photoheterotrophic $H_2$ production of Rhodobacter sphaeroides was significantly increased through disruption of the genes coding for uptake hydrogenase and poly-${\beta}$-hydroxybutyrate (PHB) synthase (Lee et al., Appl. Microbiol. Biotechnol. 60: 147-153, 2002). In this work, we further removed the B800-850 light-harvesting (LH) complex from the strain and found an increase in $H_2$ production at the light-saturating cell growth (${\ge}10$ Watts $[W]/m^2$). Neither the mutant nor the wild-type produced more $H_2$ at the brighter light. Accordingly, light does not appear to be limited for the $H_2$ production by the presence of B800-850. However, increase in the level of the spectral complexes resulted in decrease of $H_2$ production. Thus, although the B875 is essential for light harvesting, the consumption of cellular energy for the synthesis of B800-850 and the surplus LH complexes may reduce the energy flow into the $H_2$ production of R. sphaeroides.

• Transactions of the Korean hydrogen and new energy society
• /
• v.16 no.2
• /
• pp.111-121
• /
• 2005

이 연구는 광화학적 물분해 수소제소 기술의 일환으로 수행 중인 광촉매와 바이오촉매를 복합한 시스템 활용 기술에서 광촉매가 갖는 물리적 특성의 영향을 파악하고자 진행되었다. 다양한 물리적 특성을 갖는 광촉매 얻기 위하여 상용광촉매, 수열화법(HT-TiON), 리고 저온합성법(LT-TiON) 등을 이용하여 샘플을 준비하였다. 가시광 감응을 위하여 암모니아나 triethylamine 처리를 하여 질소를 도핑도 시도하였다. 시도된 복합시스템은 인위적인 전자주개 없이 수소를 발생시키는 결과를 보여주었으나, 광촉매로부터 엔자임으로의 전자전달 부분이 율속단계로 확인되었다. 사용된 광촉매 샘플에 따라 수소발생량에 차이가 나타난 결과로 광촉매의 미세구조 (결정상, 결정도, 기공 크기 및 비표면적 등)이 중요한 역할을 하는 것으로 판단되었다. 얻어진 결과들을 활용하여 재료들이 고정화된 새로운 시스템 구성을 제안하였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.478-481
• /
• 2006

Energy is vital to global prosperity, yet dependence on fossil fuels as our primary energy source contributes to global climate change environmental degradation, and health problems. Hydrogen $(H_2)$ offers tremendous potential as a clean renewable energy currency. Hydrogen has the highest gravimetric energy density of any known fuel and is compatible with electrochemical and combustion processes for energy conversion without producing carbon-based emission that contribute to environmental pollution and climate change. Numerous methodologies have been developed for effective hydrogen production. Among them, the biological hydrogen production has gained attention, because hydrogen can be produced by cellular metabolismunder the presence of water and sunlight. The green alga Chlamydomonas reinhardtii is capable of sustained $H_2$ photoproduction when grown under sulfur deprived condition. Under sulfur deprived conditions, PSII and photosynthetic $O_2$ evolution are inactivated, resulting in shift from aerobic to anaerobic condition in the culture. After anaerobiosis, sulfur deprived algal cells induce a reversible hydrogenase and start to evolve $H_2$ gas in the light. According to above principle, we investigated the effect of induction parameters such as cell age, cell density. light intensity, and sulfate concentration under sulfur deprived condition We also developed continuous hydrogen production system by sulfate re-addition under sulfur deprived condition.

• Korean Journal of Microbiology
• /
• v.24 no.2
• /
• pp.133-140
• /
• 1986

Extracts of CO-autotrophically grown cells of Acinetobacter sp. 1 were shown to use thionin, methylene blue, or 2,6-dichlorophenol-indophenol, but not NAD, NADP, FAD, or FMN, as electron acceptors for the oxidation of CO under strictly anaerobic conditions. The CO dehydrogenase (CO-DH) in the thes bacterium was found to be an inducible enzyme. The enzyme activity was determined by an assay based on the CO-dependent reduction of thionin. Maximal reaction rates were found at pH 7.5 and $60^{\circ}C$, and the Arrhenius plot revealed an activation energy of 6.1 kcal/mol(25.5kJ/mol). THe $K_m$ m/ for CO was $154{\mu}M$. Known metalchelating agents tested had no effects on the CO-DH activity. No divalent cations tested affect the enzyme activity significantly escept $Cu^{2+}$ which suppressed the activity completely. The enzyme was inhibited by glucose and succinate. The same extracts catalyzed oxidation of hydrogen gas and formate with thionin as electron acceptor. The CO-DH of Acinetobacter sp. 1 was to have no immunological relationship with that of Pseudomonas carboxydohydrogena.

• Microbiology and Biotechnology Letters
• /
• v.13 no.1
• /
• pp.79-85
• /
• 1985

Rhizobium japonicum wild type strains isolated from local soybean variety Jangback root nodules with higher nitrogenase activity than R. japonicum 3I1110 or 61A76 was mutangenized by N-methyl-N'-nitro-N-nitrosoguanidine and UV-irradiation, and screened by effectiveness assay with soybean. One mutant strain JB65 nodulated the roots earlier than the wild type and also expressed higher acetylene-reducing activity in the presence and absence of fixed nitrogen. The selected mutant was compared with SM35 strain and showed greater nodulation and symbiotic nitrogen fixing activity with local soybean variety Jangback than SM35 strain.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.8
• /
• pp.1210-1215
• /
• 2006

The properties related to the temperature and oxygen stability of the cytoplasmic hydrogenases from the fermentative strict anaerobic bacterium, Clostridium butyricum NCIB 9576 (Cl. butyricum), and purple sulfur phototrophic bacterium, Thiocapsa roseopersicina NCIB 8347 (T. roseopersicina), were compared. The optimum temperatures for the growth of Cl. butyricum and T. roseopersicina were 37$^{\circ}C$ and 25$^{\circ}C$, respectively, whereas those for the H$_2$ evolution of the cytoplasmic hydrogenases prepared from Cl. butyricum (C-H$_2$ase) and T. roseopersicina (T-H$_2$ase) were 45$^{\circ}C$ and 65$^{\circ}C$, respectively. The T-H$_2$ase was more thermostable than the C-H$_2$ase and retained its full activity for 5 h at 50$^{\circ}C$ under anaerobic conditions and 90% of its activity at 60$^{\circ}C$, whereas the C-H$_2$ase lost its activity drastically at 50$^{\circ}C$. The optimum pHs for H$_2$ oxidation of the C-H$_2$ase and T-H$_2$ase were 9.0 and 7.5, respectively. Both enzymes showed a maximum H$_2$ evolution activity at pH 7.0. Under aerobic conditions, 80% of the T-H$_2$ase activity was retained for 10 h at 30$^{\circ}C$, and 50% of the activity remained after 6 days under the same experimental conditions. However, the C-H$_2$ase was labile to oxygen and lost its activity immediately on exposure to air. Therefore, these properties of the T-H$_2$ase are expected to be advantageous for application in in vitro biological H$_2$ production systems.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.1
• /
• pp.131-135
• /
• 2005

Under sulfur deprived conditions, PS II and photosynthetic $O_2$ evolution by Chlamydomonas reinhardtii UTEX 90 are inactivated, resulting in shift from aerobic to anaerobic condition. This is followed by hydrogen production catalyzed by hydrogenase. We hypothesized that the photosynthetic capacity and the accumulation of endogenous substrates such as starch for hydrogen production might be different according to cell age. Accordingly, we investigated (a) the relationships between hydrogen production, induction time of sulfur deprivation, increase of chlorophyll after sulfur deprivation, and residual PS II activity, and (b) the effect of initial cell density upon sulfur deprivation. The maximum production volume of hydrogen was 151 ml $H_2$/l with 0.91 g/l of cell density in the late-exponential phase. We suggest that the effects of induction time and initial cell density at sulfur deprivation on hydrogen production, up to an optimal concentration, are due to an increase of chlorophyll under sulfur deprivation.

• Proceedings of the Ginseng society Conference
• /
• 1988.08a
• /
• pp.151-155
• /
• 1988

The present study was undertaken to determine the inhibitory effects of orally administered ginseng saponins(SP), protopanaxadiol saponins (PD), and protopanaxatriol saponins(PT) on the development of morphine-induced tolerance and physical dependence in mice. The study also sought to determine the hepatic glutathione contents. which are closely related to the degree of detoxification of mine the effects of GS on morphine 6-dehydrogenase, which catalyzes the production of morphinone from morphine, and the roles of spinal descendign inhibitory systems in the production of antagonism. The results of the present study showed that GS, PD and PT administered orally inhibited the development of morphine induced tolerance and dependence. GS. PD and PT inhibited the reduction of hepatic glutathione concentration in mice treated chronically with morphine and the activity of morphine 6-dehydrogenase, and the activation of spinal descending inhibitory systems was inhibited by GS. So we hypothesized that the results were partially due to the dual action of the test drugs, the inhibition of morphinone production and the activated formation of morphinone-glutathinone conjugation, and the inhibition of the activatin of apinal descending inhibitory systems and the others.

• Microbiology and Biotechnology Letters
• /
• v.13 no.3
• /
• pp.257-263
• /
• 1985

Rhodopseudomonas sp. KCTC 1437 evolved molecular hydrogen efficiently under light illuminated anaerobic culture condition in the presence of organic acids and various sugars. especially glucose when low concentration of NH$_4$ + or L-glutamate was added to cultures. It was revealed that hydrogen formation from Rhodopseudomonas sp. KCTC 1437 was mediated by two different enzyme systems. Under the nitrogen limiting condition, hydrogen evolution from glucose was catalyzed by nitrogenase. For the nitrogenase activation in vivo, the precultured cells drown on limiting concentration of NH$_4$$^{+}$ as a sole nitrogen source showed more capacity of hydrogen evolution from glucose in the presence of L-glutamate than any other cells .frown on sufficient concentration of NH$_4$$^{+}$, L-glutamate, NH$_4$$^{+}$, or both of L-glutamate and $N_2$. A significant volume of molecular hydrogen was evolved from glucose even in the presence of excess NH$_4$$^{+}$ either in the light or dark anaerobic condition, presumably due to the mediation of hydrogen evolution by fromic hydrogenlyase.enlyase.