• Environmental Engineering Research
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• 제20권1호
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• pp.51-57
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• 2015

As expected, the expression of denitrifying genes in a Typha wetland (relatively stagnant compared to other ponds), showing higher nitrogen removal efficiency in summer, was affected by temperature. The abundance and gene transcripts of nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductase (norB), and nitrous oxide reductase (nosZ) genes in seasonal sediment samples taken from the Acorus and Typha ponds of free surface flow constructed wetlands were investigated using quantitative polymerase chain reaction (Q-PCR) and quantitative reverse transcription PCR (Q-RT-PCR). Denitrifying gene copy numbers ($10^5-10^8$ genes $g^{-1}$ sediment) were found to be higher than transcript numbers-($10^3-10^7$ transcripts $g^{-1}$ sediment) of the Acorus and Typha ponds, in both seasons. Transcript numbers of the four functional genes were significantly higher for Typha sediments, in the warm than in the cold season, potentially indicating greater bacterial activity, during the relatively warm season than the cold season. In contrast, copy numbers and expression of denitrifying genes of Acorus did not provide a strong correlation between the different seasons.

• Journal of Microbiology
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• 제43권5호
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• pp.383-390
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• 2005

The diversity of the denitrifying bacterial populations in Daejeon Sewage Treatment Plant was examined using a culture-dependent approach. Of the three hundred and seventy six bacterial colonies selected randomly from agar plates, thirty-nine strains that showed denitrifying activity were selected and subjected to further analysis. According to the morphological and biochemical properties, the thirty nine isolates were divided into seven groups. This grouping was supported by an unweighted pair group method, using an arithmetic mean (UPGMA) analysis with fatty acid profiles. Restriction pattern analysis of 16S rDNA with four endonucleases (AluI, BstUI, MspI and RsaI) again revealed seven distinct groups, consistent with those defined from the morphological and biochemical properties and fatty acid profiles. Through the phylogenetic analysis using the 16S rDNA partial sequences, the main denitrifying microbial populations were found to be members of the phylum, Proteobacteria; in particular, classes Gammaproteobacteria (Aeromonas, Klebsiella and Enterobacter) and Betaproteobacteria (Acidovorax, Burkholderia and Comamonas), with Firmicutes, represented by Bacillus, also comprised a major group.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권6호
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• pp.352-356
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• 2002

Aeration was found to affect the biological denitrification by Ochrobactrum authropi SY509. Although cell growth was vigorous under 1 vvm of aeration and an agitation speed of 400 rpm in a 3-L jar fermentor, almost no nitrate was removed. Yet under low agitation speeds (100, 200, and 300 rpm), denitrification occurred when the dissolved oxygen was exhausted shortly af-ter the inoculation of the microorganism. Ochrobactrum authropi SY509 was found to express highly active denitrifying enzymes under anaerobic conditions. The microorganism also synthesized denitrifying enzymes under aerobic conditions (1 vvm and 400 rpm), yet their activity was only 60% of the maximum level under anaerobic conditions and the nitrate removal efficiency was merely 15%. However, although the activities of the denitrifying enzymes were inhibited in the presence of oxygen, they were fully recovered when the conditions were switched to anaerobic conditions.

• 한국환경보건학회지
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• 제33권4호
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• pp.338-343
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• 2007

Chlorine inhibition on the denitrifing activity of activated sludge treating dairy wastewater was investigated in this study. Filamentous bulking was caused artificially by a sudden load of feed and monitored by measuring sludge volume index. In cases of the activated sludge and bulking sludge which were contacted with chlorine as $7.5\;mgCl_2/gVSS/day$ for bulking control, the decreases of specific denitrification of $32.2{\sim}40.4%\;and\;43.5{\sim}46.5%$ were shown in comparison to the control group which was not reacted with chlorine, respectively. In continuous operation, it was observed that the removal efficiency of total nitrogen was more susceptible to chlorine than the removal efficiency of total phosphorus.

• Journal of Microbiology and Biotechnology
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• 제24권6호
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• pp.843-853
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• 2014

In the context of artificial groundwater recharge, a reactive soil column at pilot-scale (4.5 m depth and 3 m in diameter) fed by treated wastewater was designed to evaluate soil filtration ability. Here, as a part of this project, the impact of treated wastewater filtration on soil bacterial communities and the soil's biological ability for wastewater treatment as well as the relevance of the use of multi-bioindicators were studied as a function of depth and time. Biomass; bacterial 16S rRNA gene diversity fingerprints; potential nitrifying, denitrifying, and sulfate-reducing activities; and functional gene (amo, nir, nar, and dsr) detection were analyzed to highlight the real and potential microbial activity and diversity within the soil column. These bioindicators show that topsoil (0 to 20 cm depth) was the more active and the more impacted by treated wastewater filtration. Nitrification was the main activity in the pilot. No sulfate-reducing activity or dsr genes were detected during the first 6 months of wastewater application. Denitrification was also absent, but genes of denitrifying bacteria were detected, suggesting that the denitrifying process may occur rapidly if adequate chemical conditions are favored within the soil column. Results also underline that a dry period (20 days without any wastewater supply) significantly impacted soil bacterial diversity, leading to a decrease of enzyme activities and biomass. Finally, our work shows that treated wastewater filtration leads to a modification of the bacterial genetic and functional structures in topsoil.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권1호
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• pp.32-37
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• 2006

In this study, we have purified and characterized the membrane bound nitrate reductase obtained from the denitrifying bacteria, Ochrobactrum anthropi SY509, which was isolated from soil samples. O. anthropi SY509 can grow in minimal medium using nitrate as a nitrogen source. We achieved an overall purification rate of 15-fold from the protein extracted from the membrane fraction, with a recovery of approximately 12% of activity. The enzyme exhibited its highest level of activity at pH 5.5, and the activity was increased up to $70^{\circ}C$. Periplasmic and cytochromic proteins, including nitrite and nitrous oxide reductase, were excluded during centrifugation and were verified using enzyme essay. Reduced methyl viologen was determined to be the most efficient electron donor among a variety of anionic and cationic dyestuffs, which could be also used as an electron donor with dimethyl dithionite. The effects of purification and storage conditions on the stability of enzyme were also investigated. The activity of the membranebound nitrate reductase was stably maintained for over 2 weeks in solution. To maintain the stability of enzyme, the cell was disrupted using sonication at low temperatures, and enzyme was extracted by hot water without any surfactant. The purified enzyme was stored in solution with no salt to prevent any significant losses in activity levels.

• 생명과학회지
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• 제8권1호
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• pp.85-90
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• 1998

양어장에서 어류의 배설물이나 사료에 의해 생성된 암모니아성 질소 제거를 위한 수처리 공법의 하나로써 질산화 세균 및 탈질화 세균을 고정화 방법의 개잘리 필요한 실정이다. 이를 위해서는 우수한 고정화 방법의 개발이 필요한 실정이다. 이를 위해서는 우수한 질산능과 탈질능을 가지는 미생물의 분리가 선행되어야 하므로 denitifier consortium으로부터 여러 균주를 선별, 동정하여 이를 Pseudomonas sp. KH2-2으로 명명하였다. 분리된 균의 탈질능은 최적의 생육을 보일 때 가장 강하게 나타났다. $30{\circ}C보다는 40{\circ}C$에서 배양하였을 때 최적의 성장을 보여주었고, 탈질능도 현저히 높았다. pH에 있어서는 pH7에서 가장 강한 탈질능을 나타내었다. pH5에서는 균의 성장이 이루어지지 않았고 pH9에서는 $NO_3$^-환원능은 높았으나 $NO_2$^-환원능은 낮았다.

• 한국물환경학회지
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• 제36권6호
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• pp.581-591
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• 2020

In this study, two types of reactors were operated to examine the properties of methanol uptake under the high-rate denitrification process. In a sequencing batch reactor, the denitrifying activity was enriched up to 0.80 g-N/g-VSS-day for 72 days. Then, the enriched denitrifying sludge was transferred to a completely stirred tank reactor (CSTR). At the final phase on Day 46-50, the nitrogen removal efficiency was around 100% and the total nitrogen removal rate reached 0.097±0.003 kg-N/㎥-day. During the continuous process, the sludge settling index (SVI30) was stabilized as 118.3 mL/g with the biomass concentration of 1,607 mg/L. The continuous denitrifying process was accelerated by using a sequencing batch reactor (SBR) with a total nitrogen removal rate of 0.403±0.029 kg-N/㎥-day with a high biomass concentration of 8,433 mg-VSS/L. Because the reactor was open to ambient air with the dissolved oxygen range of 0.2-0.5 mg-O2/L, an increased organic carbon requirement of 5.58±0.70 COD/NO3--N was shown for the SBR in comparison to the value of 4.13±0.94 for the test of the same biomass in a completely anaerobic batch reactor. The molecular analysis based on the 16S rRNA gene showed that Methyloversatilis discipulorum and Hyphomicrobium zavarzinii were the responsible denitrifiers with the sole organic carbon source of methanol.

• 한국미생물·생명공학회지
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• 제39권3호
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• pp.210-217
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• 2011

국내의 대표적 섬이나 생태환경이 잘 보존된 토양으로부터 저영양세균 3,471주를 분리하였고 이로부터 질소발생 분석법에 의해 탈질균 135주를 최종 선발하였다. 이들 균주의 16S rDNA를 염기서열 분석한 결과 이들의 90% 가량이 Proteobacterium문에 속하였으며 다른 44속에 대부분 포함되었다. 대표적인 44속에 대해 분자생물학적 동정을 한 후 다양한 외부환경(온도, pH, 염, 무기질소염) 조건에 대한 이들의 생존성 범위를 조사한 결과, 넓은 온도($4^{\circ}C{\sim}42^{\circ}C$)와 pH(4~10)범위에서 자랄 수 있는 탈질균 12종을 최종 선발하였다.

• 한국농림기상학회지
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• 제1권2호
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• pp.160-164
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• 1999

현재 지구상에서 농업에 기인하여 배출되는 $N_2$O의 80% 정도가 지구의 온난화 뿐만 아니라 오존층 파괴에까지 영향을 미친다. 토양에서 수분함량 등과 관련한 유기태 탄소는 지하수면의 계절적 변화에 따라 탈질화를 결정하는 주요 요인이 되기도 하며 심층토의 탈질화 활동은 토양내 유기물을 분해하여 유기태 질소를 일시적으로 토양에 축적시키기도 한다. 그리고 토양의 관리방법, 폐기물의 토양처리, 질소질 비료의 시용 등이 $N_2$O 증가에 결정적 요인이 되기도 한다. 그러나 이러한 효과의 정도는 거의 알려져 있지 않을 뿐만 아니라 질산화나 탈질화와 같은 상반되는 과정과 제한 요소와 관련하여 범용적으로 적용할 수 있는 $N_2$O 방출을 예측하는 측정 계수와 같은 연구는 매우 미미한 상태이다. 그러므로 농업토양에서 비료와 유기물 시용 둥에 의해 발생하는 토양의 $N_2$O배출을 효율적으로 관리하기 위하여 심층토에서의 동적 역학적 $N_2$O 배출 측정과 관리 방법을 개발하여야 한다.