• Journal of Industrial Technology
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• v.39 no.1
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• pp.21-25
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• 2019

This work experimentally determined the effect of microaerobic condition on anaerobic digestion of thickened waste activated sludge in semi-continuous mesophilic digesters at hydraulic retention time of 20 days. The concentration of hydrogen sulfide was $7{\pm}2ppm$ at the microaerobic condition and $14{\pm}2ppm$ at the anaerobic condition. Removal efficiency of volatile solid was not significantly different between microaerobic ($40{\pm}8%$) and anaerobic ($38{\pm}8%$) conditions. There was no important difference between microaerobic ($1,352{\pm}98ml/d$) and anaerobic ($1,362{\pm}104ml/d$) conditions in the biogas production, either. Therefore, it could be concluded that the application of the microaerobic condition was an efficient method of the hydrogen sulfide removal from the biogas.

• Korean Journal of Microbiology
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• v.46 no.3
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• pp.229-232
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• 2010

Enolase is one of the glycolytic enzymes, which are involved in a central energy metabolism present in nearly all organisms. In Escherichia coli, enolase constitutes RNA degradosome with RNase E, PNPase and RNA helicase, which are involved in most mRNA degradation and RNA processing. Recently, it has been reported that RNase G, an RNase E homolog, degrades eno mRNA. To examine a functional role of RNase G in enolase expression which is known to be up-regulated under microaerobic condition, we carried out experiments. Here, we report that expression levels of enolase and RNase G are not correlated under microaerobic condition. Based on this observation, we suggest the existence of an unknown factor(s) which regulate the activity of RNase G or enolase mRNA under microaerobic conditions.

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.99-105
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• 2013

In this study, nitrous oxide ($N_2O$) emission was compared between the operations of two different sequencing batch reactors, conventional sequencing batch reactor (CNVSBR) and simultaneous nitrification and denitrification sequencing batch reactor (SND-SBR), using synthetic wastewater. The CNV-SBR consisted of anoxic (denitrification) and aerobic phases, whereas the SND-SBR consisted of a microaerobic (low dissolved oxygen concentration) phase, which was achieved by intermittent aeration for simultaneous nitrification and denitrification. The CNV-SBR emitted 3.9 mg of $N_2O$-N in the denitrification phase and 1.6 mg of $N_2O$-N in the nitrification phase, resulting in a total emission of 5.5mg from 432mg of $NH_4^+$-N input. In contrast, the SND-SBR emitted 26.2mg of $N_2O$-N under the microaerobic condition, which was about 5 times higher than the emission obtained with the CNV-SBR at the same $NH_4^+$-N input. From the $N_2O$ yield based on $NH_4^+$-N input, the microaerobic condition produced the highest yield (6.1%), followed by the anoxic (0.9%) and aerobic (0.4%) conditions. It is thought that an appropriate dissolved oxygen level is critical for reducing $N_2O$ emission during nitrification and denitrification at wastewater treatment plants.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.762-766
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• 2001

The nar promoter of Escherichia coli was known to induce maximally under anaerobic or microaerobic conditions in the presence of nitrate. In this study, the nar promoter was tested to see whether the expression level of a reporter gene which fused lacZ gene at nar promoter's downstream, in the some gram negative host strains(Agrobacterium, Pseudomonas and Rhizobium). A nar promoter system(Combination of nar promoter and gram negative strain) was grown under aerobic conditions to absorbance at 600 nm of nearly 2.0 and then, the nar promoter was induced by lowering DO to 1-2% with alternating microaerobic and aerobic condition in the fermentor cultures, using different gram negative hosts. For a wild type nar promoter (pNW61), it was possible to maintain production of ${\beta}-galactosidase$ activity per cell(specific ${\beta}-galactosidase$ activity) at 14,000, 9600, 45 Miller units in the presence of 1% nitrate. and for a nitrate - independent nar promoter (pNW618) at 12,000, 10,400 and 58 Miller units in the absence of nitrate ion, respectively.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1227-1231
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• 2004

Campylobacter, one of the emerging foodborne pathogens, is highly adaptable to the external environments by changing its morphology. In the present study, a question of whether the whole-cell antibody would still be effective for its detection even though the morphology of C. jejuni was changed was examined. When microaerophilic C. jejuni was exposed to aerobic conditions for 48 h, its morphological change was detected by confocal laser scanning microscope: Its morphology was confirmed as a spiral-bacilli form in microaerobic condition, however, as a coccoid form with a little spiral-bacilli form, when exposed to aerobic conditions. Also, the expressions of the whole-cell proteins of C. jejuni, and the suppression or induction of newly synthesized proteins in both aerobic and microaerobic conditions were analyzed by two dimensional gel electrophoresis. Additionally, immunoblotting assay with the whole cell antibody for the proteins expressed under the two conditions was performed. It was confirmed that the commercial whole-cell antibody of C. jejuni raised in rabbit was reactive. When analyzed with MALDI- TOF MS, the expressed proteins were confirmed as flagellins. Therefore, even though the morphology changed in aerobic condition, these flagellins were expressed and worked as the eitope proteins, thus making it possible to utilize for the development of an immunosensor for real-time detection of any kind of C. jejuni cell.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.754-757
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• 2001

Expression of the vhb gene encoding bacterial hemoglobin (VHb) from Vitreoscilla has been used to improve recombinant cell growth and enhance product formation under microaerobic conditions because of its ability to enhance oxygen use. We coexpressed GFP and VHb in Escherichia coli BL21 and W3110, and compared with GFP control which was not expressed VHb. We used nar oxygen-dependent inducible promoter for VHb expression. The GFP amounts in E. coli expressed VHb was about five fold higher than in the control Fluorescence intensity was increased about two fold.

• Microbiology and Biotechnology Letters
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• v.26 no.1
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• pp.7-14
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• 1998

To study the oxygen tolerance mechanism of bifidobacteria, we have studied the growth of cells, the activities of the enzymes which were related with oxygen, such as catalase, superoxide dismutase(SOD), NADH oxidase, and NADH peroxidase, and cellular fatty acid compositions of Bifidobacterium adolescentis and B. longum under anaerobic and aerated (microaerobic and aerobic) conditions. B. longum grew relatively well under the microaerobic conditions, whereas the growth of B. adolescentis was inhibited under the same aerated conditions. B. adolescentis had extremely low level of NADH oxidative enzymes while B. longum had the relatively high level of NADH oxidative enzymes, whose activities were dramatically increased from 3.7 to 11.4 times by microaerobic condition but not in B. adolescentis. The activity of SOD was unexpectedly high in B. adolescentis compared with in B. longum under anaerobic and aerated conditions. The activities of catalase were not detected in all samples tested in this study. We also found that normal $C_{l6:0}$ and $C_{18:1}$ were the major fatty acids in B. adolescentis and B. longum under anaerobic and aerated conditions. 2.2-14.1% $C_{l9:0}$ cyclo fatty acid was detected only in B. longum and the fatty acid was increased by the addition of the aeration. The $C_{l9:0}$ cyclic fatty acid was identified as a cis 9, 10-methylene octadecanoic acid, which was different from lactobacillic acid in the cyclized site. 6.6%-24.6% of dimethyl acetals (DMA) which came from plasmalogen were observed in the B. adolescentis and B. longum grown under anaerobic condition, and the components were notably decreased in the cells grown under the aerated conditions. It is believed that NADH oxidative enzymes play an important role to detoxify oxygen metabolites of Bifidobacteriurn spp. under anaerobic and microaerobic conditions. Independently from oxidative enzymes, it seems that oxygen stress may induce the change of the level of cellular fatty acids showing an increase of $C_{l9:0}$ cyclo in B. longum and a decrease of $C_{l8:1}$ of plasmalogen in B. longum and B. adolescentis to adapt in environment.

• Korean Journal of Microbiology
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• v.1 no.1
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• pp.30-37
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• 1963

Ten(10) strains of aerobic bacteria and two(2) strains of microaerobic bacteria were isolated out of soysauce which was brewed by the conventional process. The following bacteria were identified by studying their morphorogies and physiological characters. Bacillus pumillus-R-2; Bacillus subtilis var., aterimus-S-1; Bacillus licheriformis var-S-2; Bacillus subtilis-T-1; Sarcina maxima-T-2; Pediococcus acidi lactici-Z-2; Bacillus citreus var, . soyaB-Z-5. T-2 and Z-5 of the isolated bacteria were found good in growth even in the 24%-salted density, and Z-5 was more vigorous than T-2 though stinking. S-1 produced black-brown pigment from the medium containing various kinds of carbohydrate and the medium of soysauce which are available to S-1.

• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.179-185
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• 2001

Nitrate grown cells of cyanobacterium Plectonema boryanum, transferred to nitrogen stress, evolved nitrogenase catalyzed $H_2$ under microaerophilic condition. Nitrogen ($N_2$) in gs phase, low light intensity, and reducing substances in incubation phase stimulated $N_2$fixation ($H_2\;evolution$). Cyanobacterium grew slowly under microaerobic condition with a low intracellular ammonia pool. Nitrogen sources (${NO_3}^-,{NH_4}^+,\;and\;CH_3NH_3$) inhibited nitrogenase and glutamine synthetase (GS) transferase activity, and methylamine behaved like an ammonical nitrogen source. Depletion of molybdenum (Mo) and addition of tungsten (W) in the incubation medium inhibited $H_2$ evolution, Cyanobacterium was able to take up nitrate and expressed nitrate reductase (NR) activity under microaerophilic condition at an extremely slow rate.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1920-1927
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• 2015

This study aimed to optimize four factors affecting biomass accumulation and 5-aminolevulinic acid (ALA) yield together with pollutants removal in Rhodobacter sphaeroides wastewater treatment. Results showed that it was feasible to produce biomass and ALA in R. sphaeroides wastewater treatment. Microaerobic, 1,000-3,000 lux, and pH 7.0 were optimal conditions for the highest ALA yield of 4.5 ± 0.5 mg/g-biomass. Under these conditions, COD removal and biomass production rate were 93.3 ± 0.9% and 31.8 ± 0.5 mg/l/h, respectively. In addition, trace elements Fe²⁺, Mg²⁺, Ni²⁺, and Zn²⁺ further improved the ALA yield, COD removal, and biomass production rate. Specifically, the highest ALA yield (12.5 ± 0.6 mg/g-biomass) was achieved with Fe²⁺ addition.