• Journal of Microbiology and Biotechnology
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• v.31 no.5
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• pp.645-658
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• 2021

Porins are essential for the viability of Gram-negative bacteria. They ensure the uptake of nutrients, can be involved in the maintenance of outer membrane integrity and define the antibiotic or drug resistance of organisms. The function and structure of porins in proteobacteria is well described, while their function in photoautotrophic cyanobacteria has not been systematically explored. We compared the domain architecture of nine putative porins in the filamentous cyanobacterium Anabaena sp. PCC 7120 and analyzed the seven candidates with predicted OprB-domain. Single recombinant mutants of the seven genes were created and their growth capacity under different conditions was analyzed. Most of the putative porins seem to be involved in the transport of salt and copper, as respective mutants were resistant to elevated concentrations of these substances. In turn, only the mutant of alr2231 was less sensitive to elevated zinc concentrations, while mutants of alr0834, alr4741 and all4499 were resistant to high manganese concentrations. Notably the mutant of alr4550 shows a high sensitivity against harmful compounds, which is indicative for a function related to the maintenance of outer membrane integrity. Moreover, the mutant of all5191 exhibited a phenotype which suggests either a higher nitrate demand or an inefficient nitrogen fixation. The dependency of porin membrane insertion on Omp85 proteins was tested exemplarily for Alr4550, and an enhanced aggregation of Alr4550 was observed in two omp85 mutants. The comparative analysis of porin mutants suggests that the proteins in parts perform distinct functions related to envelope integrity and solute uptake.

• Membrane Journal
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• v.24 no.2
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• pp.158-166
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• 2014

In this research, microporous and bicontinuous poly vinylidene fluoride(PVDF) hollow fiber membranes were prepared via hybrid process of the thermally induced phase separation (TIPS) and stretching method. The mechanism of the membrane preparation is based on liquid-liquid phase separation. The final membranes have characteristic structures which have both bicontinuous and fibrillar morphology by applying the stretching method. They showed quite different structure when compared with the spherulitic or nodular structure from S/L TIPS and bicontinuous structure from L/L TIPS. At first, PVDF hollow fiber precursors were prepared via TIPS method using various kind of diluent mixtures. We used gamma-butyrolacton, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) as diluents. We could make hollow fiber membranes which had porous outer surface or dense outer surface by controling the parameters such as cooling conditions, PVDF concentration and the ratio of diluent mixtures. Finally, these hollow fiber were stretched at room temperature and diluents were extracted by ethanol. Effects of the stretching ratio on the membrane morphology were investigated using scanning electron microscope (SEM), and its effects on water flux, porosity, pore size, roughness and tensile strength were examined.

• Membrane Journal
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• v.31 no.5
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• pp.343-350
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• 2021

In this study the suction pressure was measured with respect to operational time by submersing the multi-bore capillary membrane module in membrane bioreactor(MBR). The hexagonal shape capillary module which has the nominal pore size of 0.2 ㎛, outer diameter of 6.4 or 4.2 mm was immersed in MLSS 8,000 mg/L active sludge aqueous solution, and confirmed changes with respect to permeation flux and air flow rate. It was operated by the filtration/relaxation(FR), FR with backwashing(FR/BW), and sinusoidal flux continuous operation(SFCO) modes. The suction pressure for the SFCO and FR modes was lower at 30 and 50 L/m²·hr, respectively. In addition, the suction pressure of the module with a small outer diameter was relatively low. The suction pressure of a large outer diameter was greatly increased, but it could be reduced by more than 40% by backwashing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.270-275
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• 2009

Sound absorption characteristics of membrane system which are used in stadiums and arenas were investigated. Theoretical studies on acoustic properties of single and double leaf permeable membrane conducted. Also, experimental studies on sound absorption characteristics of combined membrane system that is composed of outer and inner membrane material were conducted. In this study, sound absorption characteristics of each membrane were investigated by experiments in reverberation chamber. 4 types of permeable membranes and a non-permeable membrane were used for experiments. Air space behind membrane material and tension on the membrane was varied. Sound absorption performance of permeable membrane materials was confirmed. As increasing air space behind the membrane material, sound absorption coefficient was increased. In a resonance absorption frequency band sound absorption coefficient varied more dramatically. Sound absorption characteristics were flat in mid and high frequency range and sound absorption coefficient was from 0,3 to 0,5. Also sound absorption coefficient was increased by the increment of surface density and air permeability of membrane. However, over the certain value of air permeability, sound absorption coefficient was decreased. These results can be used as design factors and method for the room acoustic design of dome-stadiums and large free-form buildings.

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.9-14
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• 2009

In this study, the stress and deformation characteristics of corner protection in which is fabricated in an insulation area have been analyzed using a finite element method. The proposed corner protection may increase the strength and leakage safeties of conventional LNG storage system. The stress and deformation of LNG storage tank system are computed for an insulation panel box, membrane inner tank, and prestressed concrete outer tank. The FEM computed results indicate that the stress and displacement of new membrane LNG tank system with a corner protection between an inner tank and an outer tank are reduced in comparison to those of a conventional membrane LNG tank. This is explained that the strength safety of LNG membrane tank system may be increased due to a strength stiffness of a corner protection.

• Membrane Journal
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• v.28 no.6
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• pp.395-405
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• 2018

Poly(ethylene-co-vinylalcohol) EVOH hollow fiber membranes were successfully fabricated via a thermally induced phase separation (TIPS) method. It was observed that all membranes fabricated under different spinning conditions had interconnected and bicontinuous structures through liquid-liquid phase separation. Glycerol and poly(ethylene glycol) 200 were used as diluents for the TIPS method. Glycerol was used as a mixing component in quenching bath to control pores on the outer surface of the hollow fiber membrane. Hot quenching bath with a mixing component to generate large pores on the outer surface of the hollow fiber membrane. The effects of polymer concentration, diluent and quenching bath on the morphologies, water permeabilities, and mechanical properties of the EVOH hollow fiber membranes were systematically investigated. The relationship between water permeability, mechanical properties and spinning conditions was discussed in detail.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2241-2255
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• 2018

RSM methodology was applied to present mathematical models for the fabrication of polyvinylidene fluoride (PVDF) dual-layer hollow fibers in membrane distillation process. The design of experiments was used to investigate three main parameters in terms of polymer concentration in both outer and inner layers and the flow rate of dope solutions by the Box-Behnken method. According to obtained results, the optimization was done to present the proper membrane with desirable properties. The characteristics of the optimized membrane (named HF-O) suggested by the Box-Behnken (at the predicted point) showed that the proposed models are strongly valid. Then, a morphology study was done to modify the fiber by a combination of three types of a structure such as macro-void, sponge-like and sharp finger-like. It also improved the hydrophobicity of outer surface from 87 to $113^{\circ}$ and the mean pore size of the inner surface from 108.12 to 560.14 nm. The DCMD flux of modified fiber (named HF-M) enhanced 62% more than HF-O when it was fabricated by considering both of RSM and morphology study results. Finally, HF-M was conducted for long-term desalination process up to 100 hr and showed stable flux and wetting resistance during the test. These stepwise approaches are proposed to easily predict the main properties of PVDF dual-layer hollow fibers by valid models and to effectively modify its structure.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.1
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• pp.41-46
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• 2000

Using fluorescence polarization of 12-(9-anthroyloxy)stearic acid (12-AS) and 2-(9-anthroyloxy)stearic acid (2-AS), we evaluated the differential effects of local anesthetics on differential rotational rate between the surface (in carbon number 2 and its surroundings including the head group) and the hydrocarbon interior (in carbon number 12 and its surroundings) of the outer monolayer of the total lipid fraction liposome extracted from synaptosomal plasma membrane vesicles. The anisotropy (r) values for the hydrocarbon interior and the surface region of the liposome outer monolayer were $0.078{\pm}0.001$ and $0.114{\pm}0.001,$ respectively. This means that the rate of rotational mobility in the hydrocarbon interior is faster than that of the surface region. In a dose-dependent manner, the local anesthetics decreased the anisotropy of 12-AS in the hydrocarbon interior of the liposome outer monolayer but increased the anisotropy of 2-AS in the surface region of the monolayer. These results indicate that local anesthetics have significant disordering effects on the hydrocarbon interior but have significant ordering effects on the surface region of the liposome outer monolayer.

• Ocean and Polar Research
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• v.34 no.2
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• pp.151-163
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• 2012

Digestive cells of the bivalves have a highly developed lysosomal system and the system is known to be sensitive to changes in environmental qualities. In this study, we measured lysosomal responses of the digestive cells in wild oyster, Crassostrea gigas using frozen section. Oysters were collected in June 2010 from intertidal areas in the inner and outer bay of Gwangyang off the south coast of Korea. From the tissue sections, we measured the digestive cell lysosomal membrane stability (LMS), level of neutral lipids (NL), lipofuscin (LF) and the digestive gland atrophy (DGA). The DGA and condition index of oysters from the inner bay were significantly lower (P<0.05). The statistical test indicated that LMS levels of oysters in the inner bay and the outer bay were not significantly different since a shorter activity was displayed by oysters from the inner bay than that of oysters in outer bay. The LF deposition level of the oysters in the inner bay displayed significantly higher levels than the outer bay (P<0.05). In contrast, the NL accumulation measured from oysters in outer bay was significantly higher than the level observed in the inner bay (P<0.05). Different levels of DGA and LF that were observed in the inner and outer bays were thought to be associated to different level of environmental contamination and these two assays are considered to be good biomarkers.

• Journal of Microbiology and Biotechnology
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• v.4 no.2
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• pp.155-159
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• 1994

Two Zymomonas mobilis strains (ZM63 and ZM6307), containing both lactose and galactose operons, were constructed. $\beta$-Galactosidase and galactokinase assays indicated that both operons were expressed in both strains. The transport systems available for lactose uptake by Zymomonas mobilis were investigated using $^{14}C$-labelled lactose. After the outer membrane, which was considered to be a possible barrier to lactose uptake, was disrupted by treatment with EDTA and $Ca^{2+}$ ions, some increase in lactose uptake was observed in ZM6306 ($lac^+$) and ZM6307 ($lac^+\;gal^+$), but not in the parent, ZM6. This suggested that the outer membrane of Zymomonas mobilis acts as a barrier to lactose uptake to some degree, and also that the lactose permease is operational in Zymomonas mobilis.