Journal of Microbiology and Biotechnology (J Microbiol Biotechnol )

Publisher: Hanʼguk Sanŏp Misaengmul Hakhoe


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Publications in this journal

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    ABSTRACT: Metarhizium anisopliae is a widely studied model to understand the virulence factors that participate in pathogencity. Proteases such as subtilisin-like enzymes (Pr1) and trypsin-like enzymes (Pr2) are considered important factors for insect cuticle degradation. In four M. anisopliae strains (798, 6342, 6345, 6347), the presence of pr1 and pr2 gene, including enzymatic activity of these genes, was correlated with their virulence against two different insect pests. The 11 pr1 genes (A, B, C, D, E, F, G, H, I, J, K) and pr2 gene were found in all strains. Activity of individual Pr1 and Pr2 proteases exhibits variation in time (24, 48, 72 and 96 h) and in the presence or absence of chitin as inductor. The highest Pr1 enzymatic activity was showed by 798 strain at 48 h with chitin. The highest Pr2 enzymatic activity was exhibited by 6342 and 6347 strains, both grown with chitin at 24 and 48 h respectively. Highest mortality on S. exigua was caused by 6342 strain at 48 h, and 6342, 6345, and 6347 strains caused the highest mortality 7 days later. Mortality on Prosapia reached 30% without variation. The presence of subtilisin and trypsin genes and the activity of these proteases in M. anisopliae strains cannot be associated with the virulence against two insect pests. Probably subtilisin and trypsin enzyme production is not a vital factor for pathogenicity but its contribution is important to the pathogenicity process.
    Journal of Microbiology and Biotechnology 11/2014;
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    ABSTRACT: We investigated whether Bacillus spp., newly isolated from Korean traditional food resources, influence the resistance of hosts to foodborne pathogens by using Caenorhabditis elegans as a surrogate host model. Initially, we selected 20 Bacillus spp. that possess antimicrobial activity against various foodborne pathogens including Staphylococcus aureus. Among the selected strains, six strains of Bacillus spp. used in pre-conditioning significantly prolonged the survival of nematodes exposed to S. aureus. Based on 16S rRNA sequencing, all six strains were identified as B. licheniformis. Our findings suggest that pre-conditioning with B. licheniformis may modulate the host defense response against S. aureus.
    Journal of Microbiology and Biotechnology 06/2014;
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    ABSTRACT: L-asparaginase from gram-positive bacteria has been poorly explored. We conducted recombinant overexpression and purification of L-asparaginase from Staphylococcus sp. OJ82 (SoAsn) isolated from Korean fermented seafood to evaluate its biotechnological potential as an anti-leukemic agent. SoAsn was expressed in Escherichia coli BL21 (DE3) with an estimated molecular mass of 37.5 kDa determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Consistent with asparaginase in gram-negative bacteria, Size-exclusion chromatography determined SoAsn as a homodimer. Interestingly, optimal temperature of SoAsn was 37°C and over 90% of activity retained between 37°C and 50°C, and its thermal stability range was narrower than that of commercial E. coli L-asparaginase (EcAsn). Both SoAsn and EcAsn were active between pH 9 and pH 10, although their overall pH-dependent enzyme activities were slightly different. The Km value of SoAsn was 2.2 mM, which is higher than that of EcAsn. Among 8 metals tested for enzyme activity, cobalt and magnesium were greatly enhanced the SoAsn and EcAsn activity, respectively. Interestingly, SoAsn retained more than 60% of its activity under 2M NaCl conditions, but the activity of EcAsn was reduced to 48%. Overall, biochemical characteristics of SoAsn was similar to those of EcAsn, but its kinetics, cofactor requirements, and NaCl tolerance differed from those of EcAsn.
    Journal of Microbiology and Biotechnology 05/2014;
  • Journal of Microbiology and Biotechnology 08/2013;
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    ABSTRACT: In mice, supplementation of t10,c12 conjugated linoleic acid (CLA) increases liver mass and hepatic steatosis via increasing uptake of fatty acids released from adipose tissues. However, the effects of t10,c12 CLA on hepatic lipid synthesis and the associated mechanisms are largely unknown. Thus, we tested the hypothesis that gut microbiota-producing t10,c12 CLA would induce de novo lipogenesis and triglyceride (TG) synthesis in HepG2 cells, promoting lipid accumulation. It was found that treatment with t10,c12 CLA () for 72 h increased neutral lipid accumulation via enhanced incorporation of acetate, palmitate, oleate, and 2-deoxyglucose into TG. Furthermore, treatment with t10,c12 CLA led to increased mRNA expression and protein levels of lipogenic genes including SREBP1, ACC1, FASN, ELOVL6, GPAT1, and DGAT1, presenting potential mechanisms by which CLA may increase lipid deposition. Most strikingly, t10,c12 CLA treatment for 3 h increased phosphorylation of mTOR, S6K, and S6. Taken together, gut microbiota-producing t10,c12 CLA activates hepatic de novo lipogenesis and TG synthesis through activation of the mTOR/SREBP1 pathway, with consequent lipid accumulation in HepG2 cells.
    Journal of Microbiology and Biotechnology 01/2013; 23(11).
  • Journal of Microbiology and Biotechnology 01/2011;
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    ABSTRACT: An extremely thermostable xylanase gene, xynB, from hyperthermophilic bacterium Thermotoga maritima MSB8 was successful expressed in Kluyveromyces lactis. Response surface methodology (RSM) was applied to optimize medium components for production of XynB secreted by the recombinant K. lactis. Secretion level (102 mg/L) and enzyme activity (49 U/ml) of XynB in the optimized medium (yeast extract, lactose, and urea; YLU) were much higher than those (56 mg/L, 16 U/ml) in original medium (yeast extract, lactose, and peptone; YLP). It was also observed that the secretory efficiency of mature XynB was improved by the YLU medium. mRNA levels of 13 characterized secretion-related genes between K. lactis cultured in YLP and YLU were detected using semi-quantitative RT-PCR method. It was found that unfolded protein response (UPR) related genes such as ero1, hac1, and kar2 were up-regulated in K. lactis cultured in YLU. Therefore, nutrient ingredient, especially nitrogen source had a significant influence on the XynB secretory efficiency in the host K. lactis.
    Journal of Microbiology and Biotechnology 11/2010; 20(11):1471-80.
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    ABSTRACT: Chitinase is one of the most important mycolytic enzymes with industrial significance. This enzyme is produced by a number of organisms including bacteria. In this study we describe optimization of media components with increased production of chitinase for selected bacteria Stenotrophomonas maltophilia isolated from the soil. Different components of the defined media responsible for influencing chitinase secretion by the bacterial isolate were screened using Plackett-Burman experimental design and were further optimized by Box-Behnken factorial design of response surface methodology (RSM) in liquid culture. Maximum chitinase production was predicted in medium containing chitin 4.94 g/l, maltose 5.56 g/l, yeast extract 0.62 g/l, KH2PO4 1.33 g/l and MgSO4.7H2O 0.65 g/l using Response surface plots and point prediction tool of DESIGN EXPERT 7.1.6 (Statease, USA) software.
    Journal of Microbiology and Biotechnology 11/2010; 20(11):1597-602.