• Journal of Life Science
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• 제24권8호
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• pp.860-864
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• 2014

PAP-1, a novel antimicrobial peptide isolated from pyloric caeca extract of the starfish Asterina pectinifera was purified and characterized. First, the acidified pyloric caeca extract was put through Sep-Pak C18 solid phase extraction cartridge using a stepwise gradient. Among the eluents, RM 60 (retained materials at 60% methanol) showed good antimicrobial activity against Bacillus subtilis and Escherichia coli D31 and was purified in C18 reversed-phase and ion-exchange high-performance liquid chromatography columns. The purification steps yielded two novel peptides showing strong antimicrobial activities. These peptides were named pyloric caeca A. pectinifera peptide 1 and 2 (PAP-1 and PAP-2). For the characterization of the purified peptides, the molecular weights and amino acid sequences were determined by MALDI-TOF MS and Edman degradation. The molecular weights of PAP-1 and PAP-2 were about 2951.54 Da and 2980.15 Da respectively. The amino acid sequences of PAP-1 and PAP-2 were partially determined: AIQNAGES and AIQNAAES, respectively. PAP-2 is an isoform of PAP-1, differing merely by a single residue at position 6 (glycine or alanine). The comparison of the N-terminal amino acid sequences and molecular weights of the peptides with those of other known antimicrobial peptides revealed that PAP-1 and PAP-2 have no homology with any known peptides. These findings suggest that PAP-1 and PAP-2 play a significant role in the innate defense system of starfish pyloric caeca.

• Journal of Microbiology and Biotechnology
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• 제27권2호
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• pp.321-334
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• 2017

Process surveillance within agricultural biogas plants (BGPs) was concurrently studied by high-throughput 16S rRNA gene amplicon sequencing and an optimized quantitative microscopic fingerprinting (QMF) technique. In contrast to 16S rRNA gene amplicons, digitalized microscopy is a rapid and cost-effective method that facilitates enumeration and morphological differentiation of the most significant groups of methanogens regarding their shape and characteristic autofluorescent factor 420. Moreover, the fluorescence signal mirrors cell vitality. In this study, four different BGPs were investigated. The results indicated stable process performance in the mesophilic BGPs and in the thermophilic reactor. Bacterial subcommunity characterization revealed significant differences between the four BGPs. Most remarkably, the genera Defluviitoga and Halocella dominated the thermophilic bacterial subcommunity, whereas members of another taxon, Syntrophaceticus, were found to be abundant in the mesophilic BGP. The domain Archaea was dominated by the genus Methanoculleus in all four BGPs, followed by Methanosaeta in BGP1 and BGP3. In contrast, Methanothermobacter members were highly abundant in the thermophilic BGP4. Furthermore, a high consistency between the sequencing approach and the QMF method was shown, especially for the thermophilic BGP. The differences elucidated that using this biphasic approach for mesophilic BGPs provided novel insights regarding disaggregated single cells of Methanosarcina and Methanosaeta species. Both dominated the archaeal subcommunity and replaced coccoid Methanoculleus members belonging to the same group of Methanomicrobiales that have been frequently observed in similar BGPs. This work demonstrates that combining QMF and 16S rRNA gene amplicon sequencing is a complementary strategy to describe archaeal community structures within biogas processes.

• Journal of Microbiology and Biotechnology
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• 제27권7호
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• pp.1249-1256
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• 2017

In our search for new sources of bioactive secondary metabolites from Streptomyces sp., the ethyl acetate extracts from endophytic Streptomyces SUK 25 afforded five active diketopiperazine (DKP) compounds. The aim of this study was to characterize the bioactive compounds isolated from endophytic Streptomyces SUK 25 and evaluate their bioactivity against multiple drug resistance (MDR) bacteria such as Enterococcus raffinosus, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa, and Enterobacter spp., and their cytotoxic activities against the human hepatoma (HepaRG) cell line. The production of secondary metabolites by this strain was optimized through Thornton's medium. Isolation, purification, and identification of the bioactive compounds were carried out using high-performance liquid chromatography, high-resolution mass liquid chromatography-mass spectrometry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance, and cryopreserved HepaRG cells were selected to test the cytotoxicity. The results showed that endophytic Streptomyces SUK 25 produces four active DKP compounds and an acetamide derivative, which were elucidated as $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Leu-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Phe-{\text\tiny{L}}-Pro)$, $cyclo-({\text\tiny{L}}-Val-{\text\tiny{L}}-Phe)$, and N-(7-hydroxy-6-methyl-octyl)-acetamide. These active compounds exhibited activity against methicillin-resistant S. aureus ATCC 43300 and Enterococcus raffinosus, with low toxicity against human hepatoma HepaRG cells. Endophytic Streptomyces SUK 25 has the ability to produce DKP derivatives biologically active against some MDR bacteria with relatively low toxicity against HepaRG cells line.

• Journal of the Korean Applied Science and Technology
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• 제33권4호
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• pp.802-812
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• 2016

Silicone foam is very useful as flame resistant material for many industrial areas such as high performance gasketing, thermal shielding, vibration mounts, and press pads. A silicone foam was prepared through simultaneous crosslinking and foaming by hydrogen condensation reaction of a vinyl-containing polysiloxane (V-silicone) and a hydroxyl-containing polysiloxane (OH-silicone) with hydride containing polysiloxane (H-silicone) in the presence of platinum catalyst and imorganic filler at room temperature. This is more convenient process for silicone foam manufacturing than the conventional separated crosslinking and foaming systems. Funtionalized silicones we used in this experiment were consisted with a V-silicone containing 1,0 meq/g of vinyl groups and a viscosity of 20 Pa-s, an OH-silicone with 0.4 meq/g of hydroxyl groups and a viscosity from 50 Pa-s, and an H-silicone containing 7.5 meq/g of hydride groups and a viscosity of 0.06 Pa.s. The effects of compositions of functionalized silicones and additives, such as catalyst and filler on the structure and mechanical properties of silicone foam were studied. 0.5 wt% of Pt catalyst was enough to accelerate the foaming rate of silicone resins. The addition of OH-silicone with lower viscosity accelerates the initial foaming rate and decreases the foam density, but the addition of V-silicone with lower viscosity reduces the tensile strength as well as the elongation. The final foam density, tensile strength, and elogation of silicone foam prepared under the SF-3 condition increase maximum to $0.58g/cm^3$, $3,51kg_f/cm^2$, and 176 %, repectively. We found out the filler alumina also played an important role to improve the mechanical properties of silicone foams in our foaming system.

• Korean Chemical Engineering Research
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• 제44권2호
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• pp.187-192
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• 2006

The preparation and characterization of new polymer composite membranes containing polyphenylene oxide (PPO) thin films with hetropoly acid (HPA) are presented. PPO thin films with phosphotungstic acid (PWA) or phosphomolybdic acid (PMA) have been prepared by using the solvent mixture. The PWA and PPO can be blended using the solvent mixture, because PPO and PWA are not soluble in the same solvent. In this study, methanol was used as a solvent dissolving PWA and chloroform was used as a solvent dissolving PPO. PPO-PWA solutions were cast onto a glass plate with uniform thickness. The composite membranes were prepared by casting Nafion mixture on porous PPO-PWA films. The morphology and structure of these PPO-PWA films were observed with scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The composite membranes were characterized by measuring their ion conductivity and methanol permeability. The performance was evaluated with composite membranes as electrolytes in fuel cell conditions. The methanol cross-over of composite membranes containing PPO-PWA barrier films in the DMFC reduced by 66％.

• Food Science and Preservation
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• 제15권3호
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• pp.437-444
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• 2008

Structured lipids(SLs) were synthesized by enzymatic interesterification with DHA-enriched fish oil(containing 27% docosahexaenoic acid) and soybean oil in the hatch-type reactor. The interesterification was performed for 24 hr at $55^{\circ}C$ and TLIM(immobilized lipase from Thermonyces lanuginosa, 10% by weight of total substrates) was mixed with 180 rpm of shaking. The fish oil and soybean oil were interesterifed with several weight ratio(fish oil : soybean oil, 2:8, 3:7, 4:6, 5:5, w:w), Reverse-phase high performance liquid chromatography with an evaporative light-scattering detector separated the triglyceride species of SLs. The products contained the newly synthesized peaks. Especially, one of peaks was distinctively increased with the increasing weight ratio from 2:8 to 5:5 while the peak of trilinolein (LLL) decreased vice versa. The effect of antioxidants such as catechin, BHT(Butylated hydroxytoluene), and their combinations on the oxidative stability in SL were investigated. Oxidative stability was carried out under oven test at $60^{\circ}C$ over 72 hr thereafter SLs were analyzed for total fatty acid content, rancimat, peroxide value, electronic nose and TBARS value. Among all combinations of antioxidant, the highest stability was obtained from 200 ppm of catechin. Besides, total tocopherol ($\alpha$, $\gamma$, and $\delta$-tocopherol), iodine and saponification value were analyzed in which iodine and saponification value of SLs were 151.19 and 182.35.

• Korean Journal of Optics and Photonics
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• 제24권4호
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• pp.176-183
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• 2013

In this paper, we report the design, fabrication and characterization of the 3-Dimensional optical receiver for a Laser Detection And Ranging (LADAR) system. The optical receiver is composed of three parts; $16{\pm}16$ Geiger Mode InGaAs Avalanche Photodiode (APD) array device operated at 1560 nm wavelength, Read Out Integrated Circuit (ROIC) measuring the Time-Of-Flight (TOF) of the return signal reflected from target objects, a package and cooler maintaining the proper operational condition of the detector and control electronics. We can confirm that the LADAR system can detect the signal from a target up to 1.2 km away, and it showed low Dark Count Rate (DCR) of less than 140 kHz, and higher than 28%-Photon Detection Efficiency (PDE). This is considered to be the best performance of the $16{\pm}16$ FPA APD optical receiver for a LADAR system.

• Korean Journal of Optics and Photonics
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• 제4권1호
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• pp.15-21
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• 1993

This paper describes the design and development of a KrF excimer laser stepper and discusses the detailed system parameters and characterization data obtained from the performance test. We have developed a deep UV step-and-repeat system, operating at 248 nm, by retrofitting a commercial modules such as KrF excimer laser, precision wafer stage and fused silica illumination and 5X projection optics of numerical aperture 0.42. What we have developed, to the basic structure, are wafer alignment optics, reticle alignment system, autofocusing/leveling mechanisms and environment chamber. Finally, all these subsystem were integrated under the control of microprocessor-based controllers and computer. The wafer alignment system comprises the OFF-AXIS and the TTL alignment. The OFF-AXIS alignment system was realized with two kinds of optics. One is the magnification system with the image processing technique and the other is He-Ne laser diffraction type system using the alignment grating on the wafer. 'The TTL alignment system employs a dual beam inteferometric method, which takes advantages of higher diffraction efficiency compared with other TTL type alignment systems. As the results, alignment accuracy for OFF-AXIS and TTL alignment system were obtained within 0.1 $\mu\textrm{m}$/ 3 $\sigma$ for the various substrate on the wafers. The wafer focusing and leveling system is modified version of the conventional systems using position sensitive detectors (PSD). This type of detection method showed focusing and leveling accuracies of about $\pm$ 0.1 $\mu\textrm{m}$ and $\pm$ 0.5 arcsec, respectively. From the CD measurement, we obtained 0.4 $\mu\textrm{m}$ resolution features over the full field with routine use, and 0.3 $\mu\textrm{m}$ resolution was attainable under more strict conditions.

• Journal of Life Science
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• 제20권5호
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• pp.683-690
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• 2010

The yeast strains of Saccharomyces diastaticus produce one of three isozymes of an extracellular glucoamylase I, II or III, a type of exo-enzyme which can hydrolyse starch to generate glucose molecules from non-reducing ends. These enzymes are encoded by the STA1, STA2 and STA3 genes. Another gene, sporulation-specific glucoamylase (SGA), also exists in the genus Saccharomyces which is very homologous to the STA genes. The SGA has been known to be produced in the cytosol during sporulation. However, we hypothesized that the SGA is capable of being secreted to the extracellular region because of about 20 hydrophobic amino acid residues at the N-terminus which can function as a signal peptide. We expressed the cloned SGA gene in S. diastaticus YIY345. In order to compare the biochemical properties of the extracellular glucoamylase and the SGA, the SGA was purified from the culture supernatant through ammonium sulfate precipitation, DEAE-Sephadex A-50, CM-Sephadex C-50 and Sephadex G-200 chromatography. The molecular weight of the intact SGA was estimated to be about 130 kDa by gel filtration chromatography with high performance liquid chromatography (HPLC) column. Sodium dedecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed it was composed of two heterogeneous subunits, 63 kDa and 68 kDa. The deglycosylation of the SGA generated a new 59 kDa band on the SDS-PAGE analysis, indicating that two subunits are glycosylated but the extent of glycosylation is different between them. The optimum pH and temperature of the SGA were 5.5 and $45^{\circ}C$, respectively, whereas those for the extracellular glucoamylase were 5.0 and $50^{\circ}C$. The SGA were more sensitive to heat and SDS than the extracellular glucoamylase.

• Membrane Journal
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• 제19권4호
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• pp.341-347
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• 2009

Nanohybrid based on environmentally friendly and biodegradable polymer, poly propylene carbonate (PPC) and cloisite 20B (PPC/C-20B) have been synthesized by solution blending method and their morphology, thermal and water absorption properties have been evaluated. The structure of PPC/C-20B nanohybrid was confirmed by X-ray diffraction (XRD). The thermal property of PPC and PPC/C-20B nanohybrid were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetric (DSC). The experimental results demonstrated that nanohybrid showed the highest thermal stability in TGA and DSC. TGA tests revealed that the thermal decomposition temperature ($T_{d50%}$) of the nanohybrid increased significantly, being $23^{\circ}C$ higher than that of pure PPC while DSC measurements indicated that the introduction of 5 mass% of clay increased the glass transition temperature from 21 to $30^{\circ}C$. Further the water absorption capacity of the PPC was significantly decreased by the incorporation of clay. Water absorption cause degradation of the coating by the moistures and affect the physical and mechanical performance. This result indicates that organic modifiers have effect on thermal and water absorption capacity of PPC and are of importance for the practical process and application of PPC.