• Korean Journal of Environmental Biology
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• v.20 no.3
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• pp.237-244
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• 2002

To analyze proteins related to antifungal activity, SAR01 strain was isolated from seaweed and identified as Streptomyces sp. from the result of FAME (fatty acid methyl ester) analysis. The isolated strain had antifungal activities against T species of plant pathogenic fungi. Antifungal activity deficient mutant (SAR 535) of Streptomyces sp. SAR01 was induced by gamma radiation $(^{60}Co,\;5kGy)$. By 2 D electrophoresis analysis, 6 protein spots were found in wild strain (SAR01) but these spots disappeared in mutant strain (SAR535). Among them, 5 proteins showed similarities to heat shock protein 70(HSP70), Fe-containing superoxide dismutase II (Fe- SODII), ribosome recycling factor (RRF), 10 kDa chnperonin (GroES) and inorganic pyrophosphatase (PPAse), respectively. It suggested that the above 6 proteins could be closely related to the antifungal activity of Streptomyces sp. SAR01.

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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• pp.767-774
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• 2010

In this study, the problems of high caloric content, increased maturation time, and off-flavors in commercial beer manufacture arising from residual sugar, diacetyl, and acetaldehyde levels were addressed. A recombinant industrial brewing yeast strain (TQ1) was generated from T1 [Lipomyces starkeyi dextranase gene (LSD1) introduced, ${\alpha}$-acetohydroxyacid synthase gene (ILV2) disrupted] by introducing Saccharomyces cerevisiae glucoamylase (SGA1) and a strong promoter (PGK1), while disrupting the gene coding alcohol dehydrogenase (ADH2). The highest glucoamylase activity for TQ1 was 93.26 U/ml compared with host strain T1 (12.36 U/ml) and wild-type industrial yeast strain YSF5 (10.39 U/ml), respectively. European Brewery Convention (EBC) tube fermentation tests comparing the fermentation broths of TQ1 with T1 and YSF5 showed that the real extracts were reduced by 15.79% and 22.47%; the main residual maltotriose concentrations were reduced by 13.75% and 18.82%; the caloric contents were reduced by 27.18 and 35.39 calories per 12 oz. Owing to the disruption of the ADH2 gene in TQ1, the off-flavor acetaldehyde concentrations in the fermentation broth were 9.43% and 13.28%, respectively, lower than that of T1 and YSF5. No heterologous DNA sequences or drug resistance genes were introduced into TQ1. Hence, the gene manipulations in this work properly solved the addressed problems in commercial beer manufacture.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1197-1206
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• 2005

Vibrio vulnificus is an opportunistic pathogen that causes a septicemia and expresses numerous virulence factors, in which luxS and smcR are genes encoding for components responsible for quorum-sensing regulation. In the present study, null mutants were constructed with lesions in each or both of these two genes from the V. vulnificus Vv$\Delta$Z strain, which is a lacZ$^{-}$ and chloramphenicol/streptomycin-resistant derivative of the wild-type ATCC29307 strain, and their phenotypes related to virulence were compared with those of the parental cells. $LD_{50}$ and histopathological findings of luxS-, smcR-, or luxS- smcR- deficient mutant were not different from those of the parent strain, a lacZ-deficient streptomycin-resistant strain in mice. However, time of death in mice was delayed, and numbers of bacteria survived in bloodstream after intraperitoneal injection in mice were decreased by mutation, especially luxS and smcR double mutant (VvSR$\Delta$ZSR). These phenomena were supported by increased serum sensitivity and delayed bacterial proliferation in both murine blood and iron-restricted medium. These results suggest that the luxS and luxR homologous genes in V. vulnificus could playa role in bacterial survival in host by enhancing proliferation and adjusting to changed environment.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.565-573
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• 2019

Production of biofuels and value-added materials from cellulosic biomass requires the development of a microbial strain capable of efficiently fermenting mixed sugars. In this study, the natural xylose fermenting yeast, Pichia stipitis, was evolved to simultaneously ferment cellobiose and xylose. Serial subcultures of wild-type P. stipitis in 20 g/l cellobiose were performed to increase the rate of cellobiose consumption. A total of ten rounds of the serial subculture led to the isolation of an evolved strain fermenting cellobiose significantly faster than the parental strain. The evolved strain displayed enhanced ethanol yield from 0 to 0.4 g ethanol/g cellobiose. The evolved P. stipitis simultaneously fermented cellobiose and xylose in batch fermentation. The genetic information of our evolved P. stipitis would be valuable in the development of a microbial host for the production of biofuels and biomaterials from cellulosic biomass.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.53-60
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• 2000

Strain BH5 was isolated from naturally fermented Kimchi and identified as a bacteriocin producer, which has bactericidal activity against Micrococcus flavus ATCC 10240. Strain BH5 was identified tentatively as Lactococcus lactis by the API test and some characteristics. Lactococcus lactis BH5 showed a broad spectrum of activity against most of the non-pathogenic and pathogenic microorganisms tested by the modified deferred method. The activity of lacticin BH5, named tentatively as the bacteriocin produced by Lactococcus lactis BH5, was detected at the mid-log growth phase, reached its maximum during the early stationary phase, and decreased after the late stationary phase. Lacticin BH5 also showed a relatively broad spectrum of activity against non-pathogenic and pathogenic microorganisms as tested by the spot-on-lawn method. Its antimicrobial activity on sensitive indicator cells was completely disappeared by protease XIV or ${\alpha}$-chymotrypsin. The inhibitory activities of lacticin BH5 were detected during treatments up to 100$^{\circ}C$ for 30 min. Lacticin BH5 was very stable over a pH range of 2.0 to 9.0 and was stable with all the organic solvents examined. The cell concentration and bacteriocin production in strain BH5 were maximum when grown at 30$^{\circ}C$ in a modified MRS medium supplemented with 0.5% tryptone, 1.0% yeast extract, and 0.5% beef extract as nitrogen sources. It demonstrated a typical bactericidal mode of inhibition against Micrococcus flavus ATCC 10240. Lacticin BH5 was purified through ammonium sulfate precipitation, ethanol precipitation, and CM-Sepharose column chromatography. The apparent molecular mass of lacticin BH5 was estimated to be in the region of 3.7 kDa, by the direct detection of bactericidal activity after SDS-PAGE. Mutant strain NO141 which was isolated by nitrosoguanidine mutagenesis produced about 4 fold more bacteriocin than the wild type.

• Mycobiology
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• v.42 no.4
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• pp.361-367
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• 2014

Makgeolli, also known as Takju, is a non-filtered traditional Korean alcoholic beverage that contains various floating matter, including yeast cells, which contributes to its high physiological functionality. In the present study, we assessed the levels of ${\beta}$-glucan and glutathione in various yeast strains isolated from traditional Korean Nuruk and selected a ${\beta}$-glucan- and glutathione-rich yeast strain to add value to Makgeolli by enhancing its physiological functionality through increased levels of these compounds. Yeast ${\beta}$-glucan levels ranged from 6.26% to 32.69% (dry basis) and were strongly species-dependent. Dried Saccharomyces cerevisiae isolated from Nuruk contained $25.53{\mu}g/mg$ glutathione, $0.70{\mu}g/mg$ oxidized glutathione, and $11.69{\mu}g/g$ and $47.85{\mu}g/g$ spermidine and L-ornithine monohydrochloride, respectively. To produce functional Makgeolli, a ${\beta}$-glucan- and glutathione-rich yeast strain was selected in a screening analysis. Makgeolli fermented with the selected yeast strain contained higher ${\beta}$-glucan and glutathione levels than commercial Makgeolli. Using the selected yeast strain to produce Makgeolli with high ${\beta}$-glucan and glutathione content may enable the production of functional Makgeolli.

• Korean Journal of Microbiology
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• v.39 no.3
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• pp.155-160
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• 2003

The wild type and two morphological variants of Streptomyces viridochromogenes were studied for their lipidand fatty acid compositions at different incubation temperatures. It showed that a decrease in triacylglycerol content was closely linked to the aerial mycelium formation. Phospholipids showed no characteristic changes, except that the contents of phosphatidylethanolamine were clearly high for aerial mycelium deficient strain BR2 grown at $20^{\circ}C$. The strain BR2 also presented unidentified aminolipids with various $R_{f}$ values. Among the aminolipids, ornithinolipid increased gradually during the cultivation for all strains. The changes in fatty acid compositions showed a temperature dependency that the proportion of unsaturated acids decreased as the growth temperature increased. The proportion of straight chain saturated fatty acids decreased as the aerial mycelium developed, and it was most evident for the mutant strain M13 with more extensive aerial mycelium. The mutant strain BR2 presented significantly higher level of iso branched odd numbered saturated fatty acids.

• Korean Journal of Microbiology
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• v.26 no.4
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• pp.305-311
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• 1988

The spectinomycin resistant strain of slow growing R. japonicum R-168 was selected to be participated in conjugation with E. coli WA803/pGS9. Tn5 was introduced from suicide vector pGS9 into R. japonicum R-168 $spr^{r}$ chromosome at the frequency of $1.0\times 10^{-5}-5.0\times 10^{-7}$ and the transconjugante were selected on the yeast extract-mannitol plate containing kanamycin ($50{\mu}$g/ml) and spectinomycin ($100{\mu}$g/ml) after 8-9 days incubation. All transconjugants we tested were found to contain Tn 5 DNA on their genome, which was confirmed by Southern hybridization experiments. R. japonicum RNa75, which had been selected through plant test, was found to be defective in symbiotic nitrogen fixing ability and the production of leghemoglobin in soybean nodules formed by the inoculation of this mutant. In addition, this mutant strain hardly developed nitrogenase activity asymbiotically in contrast with the wild type strain, indicating that some nitrogen fixing gene might be blocked in this strain and the production of leghemoglobin could be decreased by the interference in nitrogen fixing genes.

• Journal of Microbiology and Biotechnology
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• v.31 no.6
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• pp.882-889
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• 2021

In order to use an enzyme industrially, it is necessary to increase the activity of the enzyme and optimize the reaction characteristics through molecular evolution techniques. We used the error-prone PCR method to improve the reaction characteristics of LipCA lipase discovered in Antarctic Croceibacter atlanticus. Recombinant Escherichia coli colonies showing large halo zones were selected in tributyrin-containing medium. The lipase activity of one mutant strain (M3-1) was significantly increased, compared to the wild-type (WT) strain. M3-1 strain produced about three times more lipase enzyme than did WT strain. After confirming the nucleotide sequence of the M3-1 gene to be different from that of the WT gene by four bases (73, 381, 756, and 822), the secondary structures of WT and M3-1 mRNA were predicted and compared by RNAfold web program. Compared to the mean free energy (MFE) of WT mRNA, that of M3-1 mRNA was lowered by 4.4 kcal/mol, and the MFE value was significantly lowered by mutations of bases 73 and 756. Site-directed mutagenesis was performed to find out which of the four base mutations actually affected the enzyme expression level. Among them, one mutant enzyme production decreased as WT enzyme production when the base 73 was changed (T→ C). These results show that one base change at position 73 can significantly affect protein expression level, and demonstrate that changing the mRNA sequence can increase the stability of mRNA, and can increase the production of foreign protein in E. coli.

• Korean Journal Plant Pathology
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• v.1 no.1
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• pp.3-11
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• 1985

Three mild mutant strains of tobacco mosaic virus (TMV) were isolated from Nicotiana tabacum var. Samsun incubated at $38^{\circ}C$ for 10 days after inoculation with a wild type of TMV-OM strain. They were designated into Tg 5272, Tw 227 and Tw 333. All mild strains could be distinguished from TMV-OM by their reactions on different indicator plants. The mild strains induced the mild mottling without distinct symptoms, whereas the wild strain produced severe mosaic, rugose and stunting on tobacco and red pepper plants. Tw 227 and Tw 333 produced smaller necrotic spots than those of Tg 5272 and TMV-OM on N. glutinosa and Datura stramonium. The former two strains also produced ring spots and mosaic on Gomphrena globosa compared with necrotic spots by the latter strains. Three mild strains were serologically identical to TMV-OM. Their physical properties were thermal inactivation point $80-85^{\circ}C$, dilution end point between $10^{-4}\;and\;10^{-6}$, and longevity in vitro 7days or longer. Ultraviolet absorption spectra of purified preparations of the mild strains and TMV-OM were identical, with a minimum at 247nm, a maximum at 260nm, and a slight shoulder at 290nm. Electrophoresis of the strains in polyacrylamide-agarose gel showed that all the strains formed one major band and two minor bands, except for one minor band of Tw 333. However, when sodium dodecyl sulfate was added to the purified viruses before electrophoresis, each strain formed only one major band.