• Korean Journal of Microbiology
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• v.39 no.3
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• pp.192-196
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• 2003

To obtain large pools of lactic acid bacteria, a strain was isolated from Tongchimi. Through its sugar fermentation and analysis of 16S rRNA gene, it was identified to be Lactobacillus plantarum HB1. This strain is Gram-positive and catalase-negative. In the range of 1～88 bp in the HB1 16S rRNA gene, the HB1 strain was homologous with other L. plantarum strains by almost 100%, and in the range of the rest 32 bp, the HB1 strain showed considerable variation, compared to other strains. Nitrate which may exist in radish can be easily converted to nitrite. The nitrite interacts with amine, and becomes nitrosamine which may cause stomach cancer. The culture obtained by HB1 strain could eliminate 400 ${\mu}M$ nitrite within 1.5 hr. It is necessary to isolate specific components which are involved in nitrite elimination in the culture and to study on its mechanism.

• KSBB Journal
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• v.18 no.4
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• pp.289-293
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• 2003

Doxorubicin is an anthracycline-family polyketide compound with a very potent anti-cancer activity, typically produced by Streptomyces peucetius. In order to increase doxurubicin productivity, a semi-industrial doxorubicin-producing Streptomyces strain named BR-Dox was cultured in a R2YE liquid medium containing CaCO$_3$, and then converted to a cell wall-free protoplast using lysozyme treatment method, followed by PEG-mediated cell wall regeneration. Among several protoplast-regenerated Streptomyces BR-Dox strains, two independent isolates named BR-Dox4 and BR-Dox6 were visually selected using thin layer chromatography (TLC) based on the pigment overproducing phenotype. Comparing with Streptomyces BR-Dox parental strain, two protoplast-regenerated strains, BR-Dox4 and BR-Dox6 exhibited 25.2％ and 12.2％ higher doxorubicin productivity analyzed by high pressure liquid chromatography (HPLC), respectively. This result suggests that a protoplast-regeneration of an antibiotics-producing Streptomyces strain should be a promising strain development approach for antibiotics overproduction in Streptomyces species.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.111-121
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• 2016

In this study, measurements were conducted by image processing to do an in-depth evaluation of strain of rebar in a uniaxial tension test. The distribution of strain and the necking region were evaluated. The image processing is used to analyze the color information of a colored image, so that the parts consistent with desired targets can be distinguished from the other parts. After this process, the image was converted to a binary one. Centroids of each target region are obtained in the binary images. After repeating such process on the images from starting point to the finishing point of the test, elongation between targets is calculated based on the centroid of each target. The tensile test were conducted on grade 60 #7(D22) and #9(D29) rebars fabricated in accordance with ASTM A615 standards. Strain results from image processing were compared to the results from a conventional strain gauge, in order to see the validity of the image processing. With the image processing, the measuring was possible in not only the initial elastic region but also the necking region of more than 0.5(50%) strain. The image processing can remove the measuring limits as long as the targets can be video recorded. It also can measure strain at various spots because the targets can easily be attached and detached. Thus it is concluded that the image processing helps overcome limits in strain measuring and will be used in various ways.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.496-501
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• 2000

Escherichia cole NZN111, which is known as a pfl ldhA double mutant strin, was metabolically engineered to produce succinic acid by overexpressing malic enzyme into the E. coli controlled by a trc promoter. Fermentation studies were carried out in a LB medium by first growing cells aerobically to an $OD_{600}$ of 5. At this point, 0.01 mM IPTG was added to induce the overexpression of malic enzyme and the agitation speed was gradually lowered. When the culture $OD_{600}$ reached 11, a complete anaerobic condition was achieved by flushing with a $CO_3-H_2$ gas mixture. When NZN111(pTrcML) was cultured at $37^{\circ}C$, the final succinic acid concentration of 2.8 g/l could be obtained after 30 h of anaerobic cultivation. The fermentation results were analyzed by the calculation of metabolic fluxes. Metaolic flux analysis showed that about 85% of phosphoenolpyruvate (PEP) was converted to pyruvate, and further converted to malic acid by malic enzyme.

• Microbiology and Biotechnology Letters
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• v.45 no.1
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• pp.43-50
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• 2017

A xylan-degrading bacterium (strain WJ-1) was isolated from soil collected from Jeju Island, Republic of Korea. Strain WJ-1 was characterized as a gram-positive, aerobic, and spore-forming bacterium. The predominant fatty acid in this bacterium was anteiso-$C_{15:0}$ (42.99%). A similarity search based on 16S rRNA gene sequences suggested that the strain belonged to the genus Streptomyces. Further, strain WJ-1 shared the highest sequence similarity with the type strains Streptomyces spinoveruucosus NBRC 14228, S. minutiscleroticus NBRC 13000, and S. glaucescens NBRC 12774. Together, they formed a coherent cluster in a phylogenetic tree based on the neighbor-joining algorithm. The DNA G+C content of strain WJ-1 was 74.7 mol%. The level of DNA-DNA relatedness between strain WJ-1 and the closest related species S. glaucescens NBRC 12774 was 85.7%. DNA-DNA hybridization, 16S rRNA gene sequence similarity, and the phenotypic and chemotaxonomic characteristics suggest that strain WJ-1 constitutes a novel subspecies of S. glaucescens. Thus, the strain was designated as S. glaucescens subsp. WJ-1 (Korean Agricultural Culture Collection [KACC] accession number 92086). Additionally, strain WJ-1 secreted thermostable endo-type xylanases that converted xylan to xylooligosaccharides such as xylotriose and xylotetraose. The enzymes exhibited optimal activity at pH 7.0 and $55^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.16 no.6
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• pp.870-879
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• 2006

The present study describes the formation of succinic acid by a nonvirulent, highly osmotolerant Klebsiella pneumoniae strain SAP (succinic acid producer), its profile of metabolites, and enzymes of the succinate production pathway. The strain produced succinate along with other metabolites such as lactate, acetate, and ethanol under aerobic as well as anaerobic growth conditions. The yield of succinate was higher in the presence of $MgCO_3$ under $N_2$ atmosphere as compared with that under $CO_2$ atmosphere. Analysis of intracellular metabolites showed the presence of a smaller PEP pool than that of pyruvate. Oxaloacetate, citrate, and $\alpha$-ketoglutarate pools were considerably larger than those of isocitrate and fumarate. In order to understand the synthesis of succinate, the enzymes involved in end-product formation were studied. Levels of phosphoenolpyruvate carboxykinase, fumarate reductase, pyruvate kinase, and acetate kinase were higher under anaerobic growth conditions. Based on the profiles of the metabolites and enzymes, it was concluded that the synthesis of succinate took place via oxaloacetate, malate, and fumarate in the strain under anaerobic growth conditions. The strain SAP showed potential for the bioconversion of fumarate to succinate under $N_2$ atmosphere in the presence of $MgCO_3$. At an initial fumarate concentration of 10 g/l, 7.1 g/l fumarate was converted to 7 g/l succinate with a molar conversion efficiency of 97.3%. The conversion efficiency and succinate yield were increased in the presence of glucose. Cells grown on fumarate contained an 18-fold higher fumarate reductase activity as compared with the activity obtained when grown on glucose.

• Environmental Engineering Research
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• v.20 no.1
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• pp.79-87
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• 2015

To treat leather industry wastewater (LIW) containing high nitrogen concentration, eight aerobic denitrifiers were isolated from sludge existing in an LIW-treatment aeration tank. Among them, one strain named as KH8 had showed the great ability in denitrification under an aerobic condition, and it was identified as Pseudomonas aeruginosa R12. The aerobic denitrification ability of the strain KH8 was almost comparable to its anaerobic denitrification ability. In lab-scale aerobic denitrifications performed in 1-L five-neck flasks for 48 hr, denitrification efficiency was found to be much improved as the strain KH8 held a great majority in the seeded cells. From the nitrogen balance at the cell-combination ratio of 10:1 (the strain KH8 to the other seven isolates) within the seeded cells, the percentage of nitrogen loss during the aerobic denitrification process was estimated to be 58.4, which was presumed to be converted to $N_2$ gas. When these seeded cells with lactose were applied to plant-scale aeration tank for 56 day to treat high-strength nitrogen in LIW, the removal efficiencies of $COD_{Cr}$ and TN were achieved to be 97.0% and 89.8%, respectively. Under this treatment, the final water quality of the effluent leaving the treatment plant was good enough to meet the water-quality standards. Consequently, the isolated aerobic denitrifiers could be suitable for the additional requirement of nitrogen removal in a limited aeration-tank capacity. To the best of our knowledge, this is the first report of aerobic denitrifiers applied to plant-scale LIW treatment.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1217-1226
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• 2004

A psychrotrophic bacterial strain, Pseudomonas fluorescens BM07, synthesized unsaturated fatty acids (UFA) from fructose in response to lowering of growth temperature, and incorporated them into both polyhydroxyalkanoic acid (PHA) and membrane lipid. The blocking of PHA synthesis by adding 5 mM 2-bromooctanoic acid to the growth medium, containing 70 mM fructose, was found to be a useful means to profile the composition of membrane lipid by gas chromatography. As the growth temperature changed from 35 to $50^{\circ}C$, the total content of two UFA, 3-hydroxy-cis-5­dodecenoic acid ($C_{12:1}$) and 3-hydroxy-cis-7-tetradecenoic acid ($C_{14:1}$), in PHA increased from 31 to 44 $mol\%$. The growth at lower temperatures also led to an increase in the level of two major UFA, palmitoleic acid (C16:1 cis9) and cis-vaccenic acid (C18:1 cis11), in membrane lipid. A fraction of these membrane-lipid UFA was converted to their corresponding cyclopropane fatty acids (CFA). The CFA conversion was a function of culture time, exhibiting biphasic increase before and after entering the stationary phase. However, pH changes in growth media had no effect on the CFA conversion, which is contrary to the case of E. coli reported. The cells grown at $30^{\circ}C$ responded to a cold shock (lowering the medium temperature down to $10^{\circ}C$) by increasing the level of C16:1 cis9 and C 18: I cis II up to that of $10^{\circ}C$-grown control cells and concomitantly decreasing the relative level of cis-9,10­methylenehexadecanoic acid (the CFA converted from C16:1 cis9) from 14 to 8 $mol\%$, whereas the 10-grown cells exhibited little change in the lipid composition when exposed to a warmer environment of $30^{\circ}C$ for 12 h. Based on this one- way response, we suggest that this psychrotrophic strain responds more efficiently and sensitively to a cold shock than to a hot shock. It is also suggested that BM07 strain is a good producer of two unsaturated 3-hydroxyacids, $C_{12:1}\;and\;C_{141:1}$.

• Microbiology and Biotechnology Letters
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• v.25 no.5
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• pp.520-526
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• 1997

Bacterial strains which degrade Arabian Light crude oil were isolated by enrichment culture from oil-spilled soil. The strain A54 was finally selected after testing emulsifying activity and oil conversion rate. Strain A54 was identified as a Acinetobacter sp. based on the morphological, biochemical and physiological characteristics. It appears to be highly specialized for growth on Arabian Light crude oil in minimal salts medium since it showed preference for oil or degradation products as substrates for growth. It was found that it could grow on at least fifteen different hydrocarbons. The optimum cultural and environmental conditions were as follows; 25$\circ$C for temperature, 7,5 for pH, 2.0% for NaCl concentration and 2.0% for crude oil concentration. Additionally, the optimal concentration of NH$_{4}$NO$_{3}$, and K$_{2}$HPO$_{4}$, were 12.5 mM and 0.057 mM, respectively. Cell growth and emulsifying activity as a function of time were also determined. Crude oil degradation and the reduction of product peaks were identified by the analysis of remnant oil by gas chromatography. Approximately 63% of crude oil were converted into a form no longer extractable by mixed organic solvents.

• KSBB Journal
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• v.26 no.6
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• pp.557-560
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• 2011

It has been known that Δ-desaturase (TAD5) in the biosynthetic pathway of long chain polyunsaturated fatty acids of Thraustochytrium aureumis responsible for the conversion of di-homo-${\gamma}$-linolenic acid (C20：4) into arachidonic acid (C20：4). The genetic sequence analysis on TAD5 of Thraustochytrium aureum ATCC34304 used in this study showed that it has two amino acid changes when compared to that of Thraustochytrium aureum TAD5 first reported in 2003. Accordingly, Thraustochytrium aureum ATCC34304 TAD5 was named TAD5_1. TAD5_1-inserted methylotropic Pichia pastoris was prepared and then cultured with a precursor fatty acid, di-homo-${\gamma}$-linolenic acid. GC analysis confirmed that a certain amount of the precursor fatty acid was converted into arachidonic acid. In this study, not only a recombinant Pichia pastoris with the typical activity of ${\Delta}5$-desaturase which plays an essential role in the biosynthesis of LCPUFAs was successfully made but also the preparationpotential of a recombinant Pichia pastoris strain which may synthesize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) that are important in maintaining and improving human's brain function was proposed.