• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2163-2173
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• 2000

The optimum pH range for biosorption of cobalt by methanotrophic bacteria was broadened to 6.0~12.0 which was compared to pH 10.5~11.5 of bios or bent-free control case. Removal efficiency of cobalt by methanotrophic biomass was pH dependent, but less sensitive than that of control. With 1.0 g biosorbent/L at initial solution pH 6.0. methanotrophic biomass took up cobalt from aqueous solutions to the extent of 170 mg/g biomass. As a result of scanning electron microscope(SEM) micrographs, cobalt removal by methanotrophic biomass seemed to be through adsorption on the surface of methanotrophic biomass and by exopolymer around the biomass. Optimum amount of methanotrophic biomass for maximum cobalt uptake was 1.0 g/L for initial 400 mg Co/L at initial pH 6.0. Removal efficiency of cobalt was slightly affected by ionic strength up to 2.0 M of NaCl and $NaNO_3$, respectively.

• Prospectives of Industrial Chemistry
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• v.19 no.2
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• pp.28-35
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• 2016

천연가스, 셰일가스 및 바이오가스의 주성분인 메탄은 지구온난화 가스로, 감축대상인 동시에 차세대 탄소 자원으로 주목을 받고 있다. 기존의 화학적 메탄전환방법은 대규모 설비투자가 요구되는 규모의 경제가 적용되어 소규모 한계 가스전에는 활용이 어렵다. 이러한 문제점을 극복하기 위하여 최근에 생물학적 전환법이 대안으로 고려되고 있다. 메탄자화균은 메탄산화효소(methane monooxygenase)를 이용하여 상온 상압에서 메탄을 탄소원으로 사용하여 생장할 수 있다. 따라서 메탄자화균의 메탄 대사경로를 기반으로 대사공학을 활용하면 메탄으로부터의 다양한 종류의 고부가가치 산물 생산이 가능하다. 본고에서는 메탄자화균을 이용한 메탄의 바이오전환 기술의 현황 및 전망에 대하여 논의하였다.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.5
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• pp.971-980
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• 2000

Mixed methanotrophs (MM) secreting soluble methane monooxygenase(sMMO) were immobilized on celite R-635 to degrade trichloroethylene(TCE) in methanotrophic consortium biofilm reactor(MCBR) system. Further neutralization of celite R-635 was not needed for immobilization because effluent pH was stabilized at neutral after 4 hour washing. It took 130 days to develop biofilm on celite R-635 and the color of the celite changed gradually from white to red. After biofilm developed, influent methane and oxygen were decreased from 2.5~4 and 8~10 ppm to 0.5~1 and 1~2 ppm, respectively, With influent 2 ppm of TCE and 10 hours of retention time, 79.9% of TCE was degraded in the MCBR system.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.991-1000
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• 2000

Methanotrophic consortium utilizing methane as the primary carbon source and secreting soluble methane monooxygenase (sMMO) was immobilized on celite R-635 to continuously treat a wastewater containing trichloroethylene (TCE). With influent 2 ppm of TCE. 80.4 and 84.5% of TCE was degraded in 6 and 20 hour of hydraulic retention time (HRT). respectively. and the removal efficiency of TCE was increased with an increase in HRT in methanotrophic consortium biofilm reactor (MCBR). With influent 5 ppm of TCE and 10 hour of HRT. average efficiency of TCE removal was decreased in initial stage. but gradually increased to 81%. TCE was degraded to 88.5 and 96.5% with 10 and 15 hour of HRT. respectively. when methane was supplied alternately with continuous oxygen supply at influent 5 ppm of TCE. The efficiency of TCE degradation was decreased probably because oxidation reaction of methane was proceeded slowly on MMO. when high concentration of methane was supplied with depletion of oxygen. As results of the pilot-scale study. biodegradation of TCE by MCBR system might be feasible at full-scale operation.

• New & Renewable Energy
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• v.19 no.4
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• pp.46-52
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• 2023

Methane is the second most emitted greenhouse gas after carbon dioxide. Despite lower emissions than those of carbon dioxide, methane receives significant attention owing to its more than 20-fold higher global warming potential. Consequently, the importance of research on methanotrophic bacteria, microorganisms capable of converting methane gas into high-value materials, is increasingly emphasized. In the case of methanotrophic bacteria, knowledge on episomal plasmids that can be used for genetic engineering remains lacking, which poses significant challenges to the engineering process. The replication origin sequences of natural plasmids within methanotrophic bacteria have been predicted through in silico methods. The basic characteristics of the replication origin, such as a high A/T ratio, repetitive sequences, and proximity to proteins related to replication, have been used as criteria for identifying the replication origin. As a result, a region with a sequence of 18 base pairs repeated eight times could be identified. The putative replication origin sequence thus identified generally takes the form of iterons, but it also possesses unique features such as the length of the gap between iterons and the repetition of identical iteron sequences. This information can be valuable for future design of episomal plasmids applicable to methanotrophs.

• KSBB Journal
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• v.13 no.4
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• pp.391-398
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• 1998

The effect of culture medium copper availability on the specific growth rate(${\mu}$) and carbon conversion efficiency (CCE) was sutided for an obligatory methanotroph Methylosinus trichosporium OB3b under various combinations of carbon and nitrogen sources. Methane or methanol was used as a carbon source, and nitrate or ammonium was used as a nitrogen source. Medium copper availability determined the intracellular location or kind of methane monooxygenase (MMO), cell-membrane (particulate or pMMO) when copper was present and cytoplasm (soluble or sMMO) when copper was deficient. When methane was used as a carbon source, copper-containing medium exhibited higher ${\mu}$ and CCE than copper-free medium regardless of the kind of nitrogen source. When methanol was used as a carbon source, however, the effect of copper disappeared. Ammonium gave the higher ${\mu}$ and CCE than nitrate for both methane and methanol. Those observation suggest that there exist an important difference in energy utilization efficiency for methane assimilation between sMMO and pMMO.

• KSBB Journal
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• v.11 no.6
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• pp.642-648
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• 1996

The effects of EDTA(Ethylene diamine tetraacetic acid), Cu, temperature, and gas(methane and oxygen) composition on methanol production from methane with Methylosinus trichosporium were investigated. In this experiment EDTA was found to be a potential methanol dehydrogenase inhibitor since it causes methanol accumulation and 6mM was found to be optimum concentration of EDTA for methanol production. When Cu was added in culture media, the produced methanol concentration level was increased. Hence it is believed that Cu enhanced the particulate methane monooxygenase formation and consequently the addition of Cu could increase the methanol production from methane. In this experiment the optimum concentration of Cu was found to be 1mM for methanol production. When temperature was shifted down from $30^{\circ}C to 25^{\circ}C$, the methanol production level was enhanced by 50%. When the ratio of methane to oxygen in gas phase was increased to 2.3 from 1, produced methanol concentration was also enhanced by 100%.

• KSBB Journal
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• v.15 no.5
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• pp.444-451
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• 2000

Nonliving methanotrophic biomass was used as biosorbent to remove lead which is one of representative pollutants in metal-bearing wastewater. Solution pH, maximum uptake, biosorbent dose and ionic strength were considered as major factors for adsorption experiments. The optimum pH range for lead removal was increased 3.8∼11.0 for methanotrophic biomass compared to biosorbent-free control, pH of 8.4∼11.2. Removal efficiency of lead by methanotrophic biomass was pH dependent, but less sensitive than that of control. In isotherm experiments with 0.2g biosorbent/L at initial solution pH 5.0, methanotrophic biomass took up lead from aqueous solutions to the extent of 1085 mg/g biomass. Removal amount of lead increased with an increase of biomass dose. According to biomass dose for initial 1000 mg Pb/L at initial pH 5.0, the optimum amount of biomass for maximum lead removal per unit methanotrophic biomass was 0.2 g biomass/L. As a result of scanning electron microscope (SEM) micrographs equipped with energy dispersive spectroscopy (EDS), lead removal by methanotrophic biomass seemed to be through adsorptions on the surface of methanotrophic biomass and exopolymers around the biomass. EDS spectra confirmed that lead adsorption appeared on the biomass and exopolymers that may be effective to lead removal comparing before and after contact with lead. Removal efficiency of lead was slightly affected by ionic strength up to 2.0 M of NaCl and NaNO$_3$respectively.

• KSBB Journal
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• v.11 no.2
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• pp.246-253
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• 1996

An obligatory methanotroph Methylosinus trichosporium OB3b was cultivated for the production of poly-${\beta}$-hydroxybutyric acid(PHB) in shake-flask using liquefied natural gas(LNG) as the sole source of carbon and energy. The maximal specific growth rate decreased by 40% using LNG compared with that obtained with pure methane. This is attributed to the inhibition by ethane and propane presents in the LNG as impurities. For the production of PHB, two-stage culture separating the production stage from the growth stage was carried out. PHB accumulation was observed after switching nutrient-sufficient to nutrient-limited condition of non-carboneous component (NO3-, PO43-, K+, Na+, Fe2+, or Mg2+). The limitation of K+ or Mg2+ resulted in relatively high PHB content, but the highest content was obtained by nitrate limitation. The optimal pH and temperature for PHB accumulation was 7.0 and $30^{\circ}C$. Under the optimal condition the maximal PHB content was about 45% after 4-day cultivation.

• KSBB Journal
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• v.10 no.2
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• pp.212-220
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• 1995

An obligatory type II methanotroph Methylosinus trichosporium OB3b was cultivated on methanol as a sole carbon and energy source. The effects of methanol concentration, pH, temperature, nitrogen source and phosphate concentration on cell growth were investigated and the results were compared with the growth on methane, which had been studied previously. When $(NH_4)_2SO_4$ was used as a nitrogen source, the maximal specific growth rate (${\mu}max$) on methanol was $0.20hr^{-1}$ and the carbon conversion efficiency(CCE) was 43%. In comparison, on methane, ${\mu}max$ and CCE were $0.08hr^{-1}$ and 32%, respectively. Ammonia was found to be a better nitrogen source for methanol-growing cells. Cell yield on nitrogen (YX/N) was the same regardless of nitrogen source as 7.14g dry cells/g N, but the yield on methanol(YX/N) was higher with ammonia(0.8g dry cells/g MeOH) than with nitrate(0.64g dry cells/g MeOH). Optimal pH and temperature were 7.0 and $30^{\circ}C$, respectively. Methanol inhibition on cell growth was observed at above 0.5%(v/v). Inhibition by phosphate was observed at above 60mM, although the inhibition on methanol dehydrogenase activity started at a much lower level of 20mM. Based on the experimental findings, the cellular physiology of M. trichosporium OB3b growing on the two closely-related carbon sources were discussed extensively.