• Journal of Microbiology
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• v.45 no.6
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• pp.521-527
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• 2007

Several yeast strains degrading malic acid as a sole carbon and energy source were isolated from Korean wine pomace after enrichment culture in the presence of malic acid. Among them, the strain designated as KMBL 5774 showed the highest malic acid degrading ability. It was identified as Issatchenkia orientalis based on its morphological and physiological characteristics as well as the nucleotide sequences of the internal transcribed spacer (ITS) 1-5.8S rDNA-ITS II region. Phylogenetic analysis of the ITS I-5.8S rDNA-ITS II sequences showed that the KMBL 5774 is the closest to I. orientalis zhuan 192. Identity of the sequences of the KMBL 5774 was 99.5% with those of I. orientalis zhuan 192. The optimal pH of the media for the growth and malic acid degradation by the yeast was between 2.0 and 3.0, suggesting that the strain is an acidophile. Under the optimized conditions, the yeast could degrade 95.5% of the malic acid after 24 h of incubation at $30^{\circ}C$ in YNB media containing 2% malic acid as a sole carbon and energy source.

• Journal of the Economic Geographical Society of Korea
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• v.10 no.3
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• pp.344-353
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• 2007

Business incubators (BIs) could be regarded as an effective mechanism for linking research and industry to inspire technology and knowledge based entrepreneurship and innovation of start-up SMEs. The performance of BIs for small and medium enterprises (SMEs) innovation should be differentiated in accordance with the technology capacity of SMEs, the national entrepreneurial culture and characters in each economy. Therefore, the research intended to categorize BIs in the selected 10 APEC member economies into four types by investigating the issue of member economies' strategies, functions and characteristics in various focused programs.

• Korean journal of food and cookery science
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• v.11 no.5
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• pp.542-547
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• 1995

Pectinesterase was isolated from the culture medium of Aspergillus japonicus and partially purified by DEAE-Sephadex batchwise, Sephadex G-75 gel filtration and ion exchange chromatography. The purified enzyme solution was completely free from polygalacturonase which depolymerizes pectin molecule. The ability of the pectinesterase to demethylate high methoxyl pectin was investigated. On 20 minute of incubation methoxyl content of low methoxyl pectin decreased from 88％ to 6.93%. In general gel prepared with the pectin containing lower methoxyl content showed the lower value of percent sag, and showed the hieher Bel strength. Textural characteristics of pectin gel determined by Rheometer showed that as the methoxyl content was lowered, hardness and resilience of the gel were increased and cohesiveness was decreased. Apple juice containing HMP and organic acids can be converted into low methoxyl pectin apple jelly by the action of pectinesterase and addition of calcium ion. The strength of low methoxyl pectin apple jelly increased when it stored at room temperature.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.10
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• pp.1411-1416
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• 2004

The objective of this work was to isolate a microorganism, able to produce high lactate dehydrogenase (LDH) activity, for use as a microbial feed additive. The LDH is an important enzyme for lactate conversion in the rumen, thereby possibly overcoming lactic acidosis owing to sudden increases of cereal in the diets of ruminants. In the present study, various bacterial strains were screened from a variety of environments. Among the isolated microorganisms, strain FFy 111-1 isolated from a Korean traditional fermented vegetable food called Kimchi showed the highest enzyme activity, along with retaining strong enzyme activity even in rumen fluid in vitro. Based on morphological and biochemical characteristics as well as compositions of cellular fatty acids plus API analyses, this strain was identified as Lactobacillus sp. The optimum temperature and pH for growth were found to be 30$^{\circ}C$ and pH 6.5, respectively. A maximum cell growth of 2.2 at $A_{650}$ together with LDH activity of 2.08 U per mL was achieved after 24 h of incubation. Initial characterization of FFy 111-1 suggested that it could be a potential candidate for use as a direct-fed microbial in the ruminant animals.

• Journal of Preventive Medicine and Public Health
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• v.53 no.6
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• pp.405-408
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• 2020

In epidemiology, the basic reproduction number (R₀) is a term that describes the expected number of infections generated by 1 case in a susceptible population. At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, R₀ was frequently referenced by the public health community and the wider public. However, this metric is often misused or misinterpreted. Moreover, the complexity of the process of estimating R₀ has caused difficulties for a substantial number of researchers. In this article, in order to increase the accessibility of this concept, we address several misconceptions related to the threshold characteristics of R₀ and the effective reproduction number (R_t). Moreover, the appropriate interpretation of the metrics is discussed. R₀ should be considered as a population-averaged value that pools the contact structure according to a stochastic transmission process. Furthermore, it is necessary to understand the unavoidable time lag for R_t due to the incubation period of the disease.

• Corrosion Science and Technology
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• v.19 no.5
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• pp.250-258
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• 2020

Recently, 5000 series and 6000 series Al alloys have been used as hull materials for small and medium-sized ships because of their excellent weldability, corrosion resistance, and durability in marine environments. Al ships can navigate at high speed due to their light weight. However, cavitation-erosion problems cause reducing durability of Al ship at high speed. In this investigation, 5052-O, 5083-H321, and 6061-T6 Al alloy materials were used to evaluate the damage characteristics with amplitude (cavitation strength). As a result of the electrochemical experiments, the corrosion current density and corrosion potential of 6061-T6 in seawater were 8.52 × 10-7 A/㎠ and -0.771 V, respectively, presenting the best corrosion resistance. The cavitation-erosion experiment showed that 5052-O had the lowest hardness value and cavitation-erosion resistance. 5052-O also had a very short incubation period. As the experiment progressed for 5052-O, pitting formed and grew in a short time, and was observed as severe cavitation-erosion damage that eliminated in large quantities. Among the three specimens, 5083-H321 presented the highest hardness value and the damage rate was the smallest after the initiation of pitting.

• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.77-86
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• 2018

The human pathogen and food spoiler Bacillus cereus can form biofilms that act as a persistent source of contamination, which is of public health concern. This study aimed to understand how the source of isolation might affect the behavior of biofilm formation. Biofilm formation abilities of 56 strains of B. cereus isolated from different environments, including human food poisoning, farm, and food, were determined. Crystal violet assay results revealed significant (p < 0.05) differences in biofilm formation abilities among the strains isolated from different sources only at an early stage of incubation. However, strain origin showed no impact on later stage of biofilm formation. Next, correlation of the group of isolates on the basis of their biofilm-forming abilities with the number of sessile cells, sporulation, and extracellular polymeric substance (EPS) formation was determined. The number of sessile cells and spores in biofilms was greatly influenced by the groups of isolates that formed dense, moderate, and weak biofilms. The contribution of extracellular DNA and/or proteins to EPS formation was also positively correlated with biofilm formation abilities. Our results that the source of isolation had significant impact on biofilm formation might provide important information to develop strategies to control B. cereus biofilm formation.

• Microbiology and Biotechnology Letters
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• v.43 no.3
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• pp.286-290
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• 2015

Lactic acid is a useful platform chemical for a wide range of food and industrial applications such as pharmaceuticals and cosmetics. Among 313 strains of lactic acid bacteria isolated from different traditional Korean fermented foods, eight Lactobacillus strains effectively utilized xylose as a carbon source to produce lactic acid. A lactic acid bacterium identified as Lactobacillus buchneri produced the highest amount of lactic acid from xylose under anaerobic conditions. The optimum xylose concentration and incubation temperature were 50 g/l and 37℃, respectively; under these conditions, 22.3 g/l lactic acid was produced.

• Journal of Microbiology and Biotechnology
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• v.4 no.2
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• pp.119-125
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• 1994

Steroid $\Delta^1$-dehydrogenase purified from hydrocortisone-induced cells of Arthrobacter simplex converted various 3-ketosteroids into their corresponding $\Delta^1$-dehydrogenated products. The transformation efficiencies depend upon the chemical structure of the steroids, especially length of the side chain at 17 position and hydroxyl groups at 11 and 17 positions. The Km values for androstenedione, the most favorable substrate examined, and hydrocortisone were 74 ${\mu}M$ and 294 ${\mu}M$, respectively. The optimum temperature and pH of the enzyme reaction were 35$^{\circ}C$ and pH 9, respectively, and the enzyme was relatively stable at the range from 20 to 35$^{\circ}C$ and from pH 5 to 10 after one hour of incubation. The enzyme activity was markedly inhibited in the presence of $Cu^{2+},\;Fe^{3+},\;Hg^{2+},\;Mo^{6+}$ ions, and somewhat inhibited by $Zn^{2+}$ and $Fe^{2+}$. $\alpha,\alpha'$-Dipyridyl that inhibits 9$\alpha$-hydroxylase and accumulates 1,4-androstadiene-3,17-dione from sterols revealed no inhibitory effect on this enzyme. EGTA showed inhibitory effect. $\beta$-Estradiol competitively inhibited the enzyme activity. Chemical modifications of the enzyme were attempted with several reagents. p-Hydroxymer-curibenzoate showed inhibition of the enzyme activity and protection of the substrate. This suggests that cysteine residue may be involved in the active site of the enzyme.

• KSBB Journal
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• v.17 no.3
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• pp.317-320
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• 2002

A bacterium(Y-5) which has potent antibacterial activity against swine atrophic rhinitis bacteria (Bordetella bronchiseptica, Pasteurella multocida) was isolated from soil and identified as a strain of Bacillus sp. Y-5 upon investigation of the morphological and physiological characteristics. The culture broth obtained from incubation of the Y-5 strain at $30^{\circ}C$ for 21 h in tryptose-bouillon agar medium (pH 6.0) showed active antibacterial activity against Bordetella bronchiseptica and the culture broth that of $30^{\circ}C$, pH 6.5, 18 h showed active antibacterial activity against Pasteurella multocida.