• Journal of Microbiology and Biotechnology
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• v.26 no.8
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• pp.1452-1456
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• 2016

Overexpression of the genes encoding phosphoeneolpyruvate carboxykinase (pckA) and NAD-dependent malic enzyme (maeA) facilitates higher intracellular ATP and NAD(P)H concentrations, respectively, under aerobic conditions in Escherichia coli. To verify a hypothesis that higher intracellular energy reserves might contribute to H₂ fermentation, wild-type E. coli strains overexpressing pckA and maeA were cultured under anaerobic conditions in a glucose minimal medium. Overexpression of pckA and maeA enabled E. coli to produce 3-times and 4-times greater H₂ (193 and 284 nmol, respectively) than the wild type (66 nmol H₂). The pckA and maeA genes were further overexpressed in a hydrogenase-3-enhanced E. coli strain. The hydrogenase-3-enhanced strain (W3110+fhlA) produced 322 nmol H₂, whereas the ATP-enhanced strain (W3110+fhlA+pckA) produced 50% increased H₂ (443 nmol). Total H₂ in the NAD(P)H-enhanced strain (W3110+fhlA+maeA) was similar to that in the control strain at 319 nmol H₂. Possible explanations for the contribution of the increased cellular energy reserves to the enhanced hydrogen fermentation observed are discussed based on the viewpoint of metabolic engineering strategy.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2009-2018
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• 2018

Leuconostoc mesenteroides can be used to produce mannitol by fermentation, but the mannitol productivity is not high. Therefore, in this study we modified the chromosome of Leuconostoc mesenteroides by genetic methods to obtain high-yield strains for mannitol production. In this study, gene knock-out strains and gene knock-in strains were constructed by a two-step homologous recombination method. The mannitol productivity of the pat gene (which encodes phosphate acetyltransferase) deletion strain (${\Delta}pat::amy$), the fk gene (which encodes fructokinase) deletion strain (${\Delta}fk::amy$) and the stpk gene (which encodes serine-threonine protein kinase) deletion strain (${\Delta}stpk::amy$) were all increased compared to the wild type, and the productivity of mannitol for each strain was 84.8%, 83.5% and 84.1%, respectively. The mannitol productivity of the mdh gene (which encodes mannitol dehydrogenase) knock-in strains (${\Delta}pat::mdh$, ${\Delta}fk::mdh$ and ${\Delta}stpk::mdh$) was increased to a higher level than that of the single-gene deletion strains, and the productivity of mannitol for each was 96.5%, 88% and 93.2%, respectively. The multi-mutant strain ${\Delta}dts{\Delta}ldh{\Delta}pat::mdh{\Delta}stpk::mdh{\Delta}fk::mdh$ had mannitol productivity of 97.3%. This work shows that multi-gene knock-out and gene knock-in strains have the greatest impact on mannitol production, with mannitol productivity of 97.3% and an increase of 24.7% over wild type. This study used the methods of gene knock-out and gene knock-in to genetically modify the chromosome of Leuconostoc mesenteroides. It is of great significance that we increased the ability of Leuconostoc mesenteroides to produce mannitol and revealed its broad development prospects.

• Journal of Microbiology and Biotechnology
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• v.33 no.2
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• pp.167-179
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• 2023

The rifampicin-resistant strain E9-302 of Edwardsiella ictaluri strain 669 (WT) was generated by continuous passage on BHI agar plates containing increasing concentrations of rifampicin. E9-302 was attenuated significantly by 119 times to zebrafish Danio rerio compared to WT in terms of the 50% lethal dose (LD₅₀). Zebrafish vaccinated with E9-302 via intraperitoneal (IP) injection at a dose of 1 × 10³ CFU/fish had relative percentage survival (RPS) rates of 85.7% when challenged with wild-type E. ictaluri via IP 14 days post-vaccination (dpv). After 14 days of primary vaccination with E9-302 via immersion (IM) at a dose of 4 × 10⁷ CFU/ml, a booster IM vaccination with E9-302 at a dose of 2 × 10⁷ CFU/ml exhibited 65.2% RPS against challenge with wild-type E. ictaluri via IP 7 days later. These results indicated that the rifampicin-resistant attenuated strain E9-302 had potential as a live vaccine against E. ictaluri infection. A previously unreported amino acid site change at position 142 of the RNA polymerase (RNAP) β subunit encoded by the gene rpoB associated with rifampicin resistance was identified. Analysis of the whole-genome sequencing results revealed multiple missense mutations in the virulence-related genes esrB and sspH2 in E9-302 compared with WT, and a 189 bp mismatch in one gene, whose coding product was highly homologous to glycosyltransferase family 39 protein. This study preliminarily explored the molecular mechanism underlying the virulence attenuation of rifampicin-resistant strain E9-302 and provided a new target for the subsequent study of the pathogenic mechanism of E. ictaluri.

• Korean Journal of Microbiology
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• v.17 no.1
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• pp.25-41
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• 1979

A strain able to grow up m-toluate minimal medium has been isolated after selective enrichment and given the name T81X, which was later identified as pseudomonase putida according to its morphological and biochemical characteristics. After treatment with plasmied specific curing agent, mitomycin C, followed by replica plating on m-toluate and xylene minimal agar plate, T81Xstrain has been shown to harbour a curable plasmid relating to the m-toluate and xylene metabolism. Spontaneous curing frquency of this plasmid was also greatly enhanced by growing on benzoate minimal medium. After then, it was also xylene metabogrowing on benzoate minimal medium. After then, it was found to be conjugally nontransmissible. From the comparative investigation of catechol 1,2-oxygenase and catechol 2,3-oxygenase activities in wild type and cured strain on various growth substrate, it appeared that T81X strain has both of these two enzymes while cured strain has catechol 1,2-oxygenase only. Growing on m-toluate minimal medium T81X strain should carry the genetic information necessary for coding the catechol 1,2-oxygense induced by m-toluate or benzoate, on that curable plasmid.

• The Korean Journal of Mycology
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• v.1 no.1
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• pp.23-28
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• 1973

The soil of Kwangneung area(Kyeunggi-Do) was inoculated directly into wheat-bran-media and after $3{\sim}4$ days of incubation, a Penicillium species whose cellulase activity was 1011u/g was isolated. With the treatment of mutagenic agents an improved strain(cellulase activity: 1303u/g) was obtained. This strain was screened again by mono-spore isolation method. Finally a strain C8-14 (cellulase activity: 2351u/g) which had lesser spores than the wild strain was obtained.

• Mycobiology
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• v.37 no.4
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• pp.267-271
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• 2009

A fungal strain producing a high level of cellulase was selected from 320 fungal isolates and identified as Aspergillus sp. This strain was further improved for cellulase production by sequential treatments by two repeated rounds of $\gamma$-irradiation of $Co^{60}$, ultraviolet treatment and four repeated rounds of treatment with N-methyl-N'-nitro-N-nitrosoguanidine. The best mutant strain, Aspergillus sp. XTG-4, was selected after screening and the activities of carboxymethyl cellulase, filter paper cellulase and $\beta$-glucosidase of the cellulase were improved by 2.03-, 3.20-, and 1.80-fold, respectively, when compared to the wild type strain. After being subcultured 19 times, the enzyme production of the mutant Aspergillus sp. XTG-4s was stable.

• Journal of Microbiology and Biotechnology
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• v.6 no.5
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• pp.315-320
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• 1996

The role of glyoxylate bypass in a lysine-producing Corynebacterium lactofermentum strain was analyzed. Unlike the wild type, the strain expressed enzymes of glyoxylate bypass during growth in the fermentation broth containing glucose as the carbon source. To evaluate the importance of glyoxylate bypass in the strain, we disrupted chromosomal aceA by using a cloned fragment of the gene. Site-specific disruption of aceA which codes for the isocitrate lyase, the first enzyme of the bypass, was confirmed by Southern blot analysis. The aceA mutant strain completely lost isocitrate lyase activity and ability to grow in a minimal medium containing acetate as the sole carbon source. The mutant strain was similar to its parental strain in growth characteristics and produced comparable amounts of lysine in shake flasks containing glucose as the carbon source. The amount of oxaloacetate accumulated in the fermentation medium was similar for both strains, suggesting that expression of glyoxylate bypass does not necessarily lead to the increase in intracellular oxaloacetate. These data clearly demonstrate that glyoxylate bypass does not function as one of the routes of carbon supply for lysine production in the strain. It appears that the leakiness of the glyoxylate bypass in the strain might be the result of a secondary mutation which arose during previous strain development by random mutagenesis.

• The Korean Journal of Mycology
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• v.44 no.2
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• pp.87-93
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• 2016

From 182 non-pathogenic wild yeast isolates from flowers, Pichia silvicola UL6-1 and Sporobolomyces carnicolor 402-JB-1 were selected for potent ${\gamma}$-aminobutyric acid production and microbiological characteristics were investigated. Pichia silvicola UL6-1 formed ascospores and pseudomycelia. The strain was also halotolerant, growing well in 5% NaCl-containing yeast extract-peptone-dextrose (YPD) medium. Sporobolomyces carnicolor 402-JB-1 did not form ascospores or pseudomycelia and grew well on 10% glucose-yeast extract-peptone medium.

• Journal of Mushroom
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• v.7 no.2
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• pp.49-56
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• 2009

This study was conducted to preserve of mushroom resources and utility useful wild mushrooms by segregation and identification from 2005 to 2007. The mushroom strains were collected a center of native mushroom wild growth place of Chungbuk Province. The obtained results from this study were summarized as follows ; We collected 79 wild mushroom strains, and the collected wild mushrooms were composition of 32 strains of edible mushrooms, 3 strains of medicinal use mushrooms, 15 strains of poisonous mushrooms, and 29 strains indistinct mushrooms. The 28 strains were segregated and identified from 32 strains of edible mushrooms. The present preservation strains are 15 strains, and other 13 strains were damaged in tissue culture and preservation. We made specimen of wild mushroom by alcohol, and have preserved perennial mushrooms by drying. We photographed 79 strains of wild mushrooms.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.2
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• pp.188-199
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• 1996

The native ecological environment and aromatic constituents of Korean wild Codonopsis lanceolata and one Japanese strain were investigated to find Codonopsis lanceolata strains showing high aromatics, and to know regional differences among these strains. The results were as follows : There were no remarkable differences among the Korean wild C. lanceolata strains in ecological environments. Recovery yield of essential oils was highest in Togyusan strain with 0.009%. Difference in protein band patterns among these strains was not recognized, and peroxidase and esterase pattern changes were appeared in different collected regions at the leaf and root tissues. Major aromatic constituents were 11 kinds of aliphatic alcohols such as trans-2-hexenal, 1-hexanol, cis-3-hexanol, and trans-2-hexanol. And Togyusan strain, Sobaeksan strain, and Kayasan strain have the highest aliphatic alcohols of plant essential oils. In particular, BHT(butylated hydroxytoluene), one of the antioxidants, was detected in Chirisan strains.