• Journal of Microbiology and Biotechnology
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• 제31권10호
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• pp.1455-1464
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• 2021

Trehalose is a non-reducing disaccharide in increasing demand for applications in food, nutraceutical, and pharmaceutical industries. Single-step trehalose production by trehalose synthase (TreS) using maltose as a starting material is a promising alternative process for industrial application due to its simplicity and cost advantage. Pseudomonas monteilii TBRC 1196 was identified using the developed screening method as a potent strain for TreS production. The TreS gene from P. monteilii TBRC 1196 was first cloned and expressed in Escherichia coli. Purified recombinant trehalose synthase (PmTreS) had a molecular weight of 76 kDa and showed optimal pH and temperature at 9.0 and 40℃, respectively. The enzyme exhibited >90% residual activity under mesophilic condition under a broad pH range of 7-10 for 6 h. Maximum trehalose yield by PmTreS was 68.1% with low yield of glucose (4%) as a byproduct under optimal conditions, equivalent to productivity of 4.5 g/l/h using enzyme loading of 2 mg/g substrate and high concentration maltose solution (100 g/l) in a lab-scale bioreactor. The enzyme represents a potent biocatalyst for energy-saving trehalose production with potential for inhibiting microbial contamination by alkaline condition.

• 융합정보논문지
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• 제11권9호
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• pp.115-123
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• 2021

본 연구는 산말 3종류 Desmarestia dudresnayi subsp. Tabacoides (담배잎산말), Desmarestia viridis (쇠꼬리산말), Desmarestia ligulate (참산말) 잎 추출물의 항산화 및 항 멜라닌 활성에 대한 기능적 연구를위해 수행하였다. 3종류의 산말 중 담배잎산말 추출물이 2.5 mg / mL의 농도에서 DPPH 및 ABTS 라디칼 소거활성이 각각 68.0 % ± 1.9 % 및 84.6 % ± 1.7 %로 강한 항산화력을 나타냈다. 질소 (NO) 라디칼 소거 활성은 91.6 % ± 1.1 %의 높은 항산화능을 보였다 산말 추출물을 이용한 B16F10세포의 세포독성은 100 ㎍/mL 농도에서 3종의 산말 추출물이 모두 85% 이상의 세포 생존률을 보였고, 100 ㎍ / mL농도에서 담배잎산말 및 쇠꼬리산말이 70% 이상의 멜라닌 억제효과를 보였다. 이러한 내용은 산말이 항산화 및 항멜라닌 활성과 같은 천연 화장품 소재로 사용될 수 있을 것으로 사료된다.

• Journal of Microbiology and Biotechnology
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• 제31권9호
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• pp.1191-1199
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• 2021

Enteropathogenic Escherichia coli (EPEC), which belongs to the attaching and effacing diarrheagenic E. coli strains, is a major causative agent of life-threatening diarrhea in infants in developing countries. Most EPEC isolates correspond to certain O serotypes; however, many strains are non-typeable. Two EPEC strains, EPEC001 and EPEC080, which could not be serotyped during routine detection, were isolated. In this study, we conducted an in-depth characterization of their putative O-antigen gene clusters (O-AGCs) and also performed constructed mutagenesis of the O-AGCs for functional analysis of O-antigen (OAg) synthesis. Sequence analysis revealed that the occurrence of O-AGCs in EPEC001 and E. coli O132 may be mediated by recombination between them, and EPEC080 and E. coli O2/O50 might acquire each O-AGC from uncommon ancestors. We also indicated that OAg-knockout bacteria were highly adhesive in vitro, except for the EPEC001 wzy derivative, whose adherent capability was less than that of its wild-type strain, providing direct evidence that OAg plays a key role in EPEC pathogenesis. Together, we identified two EPEC O serotypes in silico and experimentally, and we also studied the adherent capabilities of their OAgs, which highlighted the fundamental and pathogenic role of OAg in EPEC.

• Plant Breeding and Biotechnology
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• 제5권3호
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• pp.192-203
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• 2017

Metabolite profile is a powerful analytical technique to identify the functional characterization of plants. In this study, the phytochemicals and secondary metabolites of lentils (Lens culinaris) were analyzed to compare the anti-oxidative activities according to the different colors. The polar metabolites, fatty acids, carotenoids, flavonoids, anthocyanins, total phenolic acids, DPPH activity were analyzed. Three kind of lentils, French green whole lentil (FG), red whole lentil (LR), and green whole lentil (LG) (ASIA SEED Co., LTD), were used for this study. Fatty acids, phytochemicals, and antioxidative components from each lentil varieties were analyzed by official methods. The contents of lutein in carotenoids were 6-9 times higher than zeaxanthin in all lentils, but were not significantly different among three varieties. The content of carotenoids in FG was lower significantly than those in the LR and LG. Myricetin and luteolin were detected in the only FG. Kaempferol and delphinidin were significantly highest in the FG. Most of the phenolic acids except coumarate were higher in FG and LG than in LR. Also antioxidant effects ($EC_{50}$) were higher in FG and LG than in LR. The analyzed metabolites obtained from lentils showed distinct separation in the PCA results according to the varieties. Also, lentils showed different anti-oxidant profiles according to the colors. FG and LG showing higher contents of phytochemicals showed higher antioxidative activity than LG containing relative low contents of phytochemicals.

• 한국육종학회지
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• 제42권1호
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• pp.1-10
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• 2010

Five mutants were investigated at the molecular level to determine the factors responsible for mutated endosperm types. They were classified as high (HA) or low amylose (LA) phenotypes based on the amylose content in endosperm. The five were previously produced from Ilpum and Shindongjin cultivar treated with N-methyl-N-nitrosourea and gamma-ray irradiation, respectively. Analysis of the genomic structure and expression of Granule-bounded Starch Synthase I (GBSSI) genes revealed that mutants generally showed a higher incidence of nucleotide transition than transversion, and the $A:T{\rightarrow}G:C$ transition was particularly prevalent. The rates of nucleotide substitution in HA mutants were generally higher than those in the LA mutants, leading to higher substitutions of amino acid in the HA mutants. Neither nucleotide substitutions interfering with intron splicing or causing early termination of protein translation were found, nor any large-sized deletions or additions were found in all the mutants. In principle, amylose content can be regulated by three factors: internal alterations of GBSSI protein, the strength of gene expression, and other unknown external factors. Our results indicate that the endosperm mutants from Shindongjin arose from internal alterations of GBSSI proteins, which may be the result of amino acid substitutions. On the other hand, the Ilpum mutants might be principally caused by the alteration of gene expression level. Analysis of another three glutinous cultivars revealed that the major factor leading to glutinous phenotypes is the 23-bp duplicative motif (5'-ACGGGTTCCAGGGCCTCAAGCCC-3') commonly found in exon 2, which results in the premature termination of protein translation leading to the production of a non-functional GBSSI enzyme.

• Journal of Microbiology and Biotechnology
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• 제29권4호
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• pp.577-586
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• 2019

The engineered Aspergillus oryzae has a high NADPH demand for xylose utilization and overproduction of target metabolites. Glucose-6-phosphate dehydrogenase (G6PDH, E.C. 1.1.1.49) is one of two key enzymes in the oxidative part of the pentose phosphate pathway, and is also the main enzyme involved in NADPH regeneration. The open reading frame and cDNA of the putative A. oryzae G6PDH (AoG6PDH) were obtained, followed by heterogeneous expression in Escherichia coli and purification as a his6-tagged protein. The purified protein was characterized to be in possession of G6PDH activity with a molecular mass of 118.0 kDa. The enzyme displayed maximal activity at pH 7.5 and the optimal temperature was $50^{\circ}C$. This enzyme also had a half-life of 33.3 min at $40^{\circ}C$. Kinetics assay showed that AoG6PDH was strictly dependent on $NADP^+$ ($K_m=6.3{\mu}M$, $k_{cat}=1000.0s^{-1}$, $k_{cat}/K_m=158.7s^{-1}{\cdot}{\mu}M^{-1}$) as cofactor. The $K_m$ and $k_{cat}/K_m$ values of glucose-6-phosphate were $109.7s^{-1}{\cdot}{\mu}M^{-1}$ and $9.1s^{-1}{\cdot}{\mu}M^{-1}$ respectively. Initial velocity and product inhibition analyses indicated the catalytic reaction followed a two-substrate, steady-state, ordered BiBi mechanism, where $NADP^+$ was the first substrate bound to the enzyme and NADPH was the second product released from the catalytic complex. The established kinetic model could be applied in further regulation of the pentose phosphate pathway and NADPH regeneration of A. oryzae to improve its xylose utilization and yields of valued metabolites.

• Molecules and Cells
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• 제42권3호
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• pp.262-269
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• 2019

The porcine myeloid antimicrobial peptide (PMAP), one of the cathelicidin family members, contains small cationic peptides with amphipathic properties. We used a putative lysozyme originated from the bacteriophage P22 (P22 lysozyme) as a fusion partner, which was connected to the N-terminus of the PMAP36 peptide, to markedly increase the expression levels of recombinant PMAP36. The PMAP36-P22 lysozyme fusion protein with high solubility was produced in Escherichia coli. The final purified yield was approximately 1.8 mg/L. The purified PMAP36-P22 lysozyme fusion protein exhibited antimicrobial activity against both Gram-negative and Grampositive bacteria (Staphylococcus aureus, Salmonella enterica serovar Typhimurium, Pseudomonas aeruginosa, and Bacillus subtilis). Furthermore, we estimated its hemolytic activity against pig erythrocytes as 6% at the high concentration ($128{\mu}M$) of the PMAP36-P22 lysozyme fusion protein. Compared with the PMAP36 peptide (12%), our fusion protein exhibited half of the hemolytic activity. Overall, our recombinant PMAP36-P22 lysozyme fusion protein sustained the antimicrobial activity with the lower hemolytic activity associated with the synthetic PMAP36 peptide. This study suggests that the PMAP36-P22 lysozyme fusion system could be a crucial addition to the plethora of novel antimicrobials.

• Journal of Microbiology and Biotechnology
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• 제29권2호
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• pp.244-255
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• 2019

Xylose isomerase (XI; E.C. 5.3.1.5) catalyzes the isomerization of xylose to xylulose, which can be used to produce bioethanol through fermentation. Therefore, XI has recently gained attention as a key catalyst in the bioenergy industry. Here, we identified, purified, and characterized a XI (PbXI) from the psychrophilic soil microorganism, Paenibacillus sp. R4. Surprisingly, activity assay results showed that PbXI is not a cold-active enzyme, but displays optimal activity at $60^{\circ}C$. We solved the crystal structure of PbXI at $1.94-{\AA}$ resolution to investigate the origin of its thermostability. The PbXI structure shows a $({\beta}/{\alpha})_8$-barrel fold with tight tetrameric interactions and it has three divalent metal ions (CaI, CaII, and CaIII). Two metal ions (CaI and CaII) located in the active site are known to be involved in the enzymatic reaction. The third metal ion (CaIII), located near the ${\beta}4-{\alpha}6$ loop region, was newly identified and is thought to be important for the stability of PbXI. Compared with previously determined thermostable and mesophilic XI structures, the ${\beta}1-{\alpha}2$ loop structures near the substrate binding pocket of PbXI were remarkably different. Site-directed mutagenesis studies suggested that the flexible ${\beta}1-{\alpha}2$ loop region is essential for PbXI activity. Our findings provide valuable insights that can be applied in protein engineering to generate low-temperature purpose-specific XI enzymes.

• Metals and materials international
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• 제24권6호
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• pp.1359-1368
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• 2018

The mechanical properties and microstructure evolution of Mg-8Li-3Al-1Y alloy undergoing different rolling processes were systematically investigated. X-ray diffraction, optical microscope, scanning electron microscopy, transmission electron microscopy as well as electron backscattered diffraction were used for tracking the microstructure evolution. Tensile testing was employed to characterize the mechanical properties. After hot rolling, the $MgLi_2Al$ precipitated in ${\beta}-Li$ matrix due to the transformation reaction: ${\beta}-Li{\rightarrow}{\beta}-Li+MgLi_2Al+{\alpha}-Mg$. As for the alloy subjected to annealed hot rolling, ${\beta}-Li$ phase was clearly recrystallized while recrystallization rarely occurred in ${\alpha}-Mg$ phase. With regard to the microstructure undergoing cold rolling, plenty of dislocations and dislocation walls were easily observed. In addition, the microstructure of alloys subjected to annealed cold rolling revealed the formation of new fresh ${\alpha}-Mg$ grains in ${\beta}-Li$ phase due to the precipitation reaction. The mechanical properties and fracture modes of Mg-8Li-3Al-1Y alloys can be effectively tuned by different rolling processes.

• Asian-Australasian Journal of Animal Sciences
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• 제32권3호
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• pp.413-420
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• 2019

Objective: This study investigated the effects of dry radish leaf and root on the quality of pork patties during refrigeration storage. Methods: The patties were divided into the following three groups: the control containing 0% dry radish leaf root powder, RL1 containing 0.5% dry radish leaf root powder, and RL2 and RL3 containing 1% and 2% dry radish leaf root powder, respectively. Proximate composition, pH, cooking loss, microbial analysis, lipid oxidation analysis, color, texture profile analysis and sensory test were performed. Results: Moisture, crude protein, and crude ash contents in RL2 and RL3 were significantly higher than those in other groups (p<0.05), whereas crude fat contents in RL2 and RL3 were significantly lower than other groups (p<0.05). Lightness was significantly lower in RL2 and RL3 than in CON (p<0.05). Cooking loss for RL2 and RL3 were significantly lower than those for the other groups (p<0.05). The pH, thiobarbituric acid levels, and total plate counts of RL2 and RL3 were significantly lower than those of CON at days 7 and 14 (p<0.05). Hardness values of RL2 and RL3 were significantly lower than those of CON, whereas chewiness values were higher than those of CON (p<0.05). In addition, the juiciness of RL2 were significantly greater (p<0.05) than those of the other groups. Conclusion: Dried radish leaves and roots improved the proximate composition and quality characteristics of pork patties, providing a basis to produce high-quality patties with extended expiration dates. Thus, dried radish leaves and roots are effective ingredients for health or functional foods.