• YAKHAK HOEJI
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• v.42 no.4
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• pp.353-358
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• 1998

The MeOH extract of the bark of Paeonia moutan showed potent inhibitory effect on the mushroom tyrosinase activity in vitro. The activity-guided fractionation of t he MeOH extract resulted in the isolation of three active compounds. The chemical structures of these compounds were elucidated by chemical and spectroscopic evidence as catechin, 1,2,3,6-tetra-O-galloyl-${\beta}$-D-glucose and 1,2,3,4,6-penta-0-galloyl-${\beta}$-D-glucose, respectively. Among them, the inhibitory activity by 1,2,3,6-tetra-galloyl-${\beta}$-D-glucose on mushroom tyrosinase was more potent $(IC_{50}=3.5\;{\mu}M)$ than that of kojic acid $(IC_{50}=8.7\;{\mu}M)$ ,but catechin enhanced the mushroom tyrosinase activity 50% in the concentration of 34.5M.

• Journal of Environmental Science International
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• v.5 no.1
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• pp.43-50
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• 1996

Thiobacillus neopolitanus R-10, which produces a active thiosulfate oxidase was isolated from nightsoil. The optimal culture conditions of Thiobacillus neopolitanus R-10 for the production of enzyme was determined as followed: 0.8% $Na_2S_2O_3$, 0.2% $KH_2PO_4$, 0.2% $K_2HPO_4$, 0.04% $Na_2CO_3$, 0.02% $MgSO_4$.$7H_2O$, 2ml trace elements solution, ann PH 6.5 at 3$0^{\circ}C$ and 72hr cultivation. The oxidase was successively purified 83 folds yield by ${(NH_2)}_2SO_4$ fractionation, DEAE-Cellulose, Sephadex A-50 column chromatogrophy and gel Sephadex G-150 gel filteration with yield of 5.9%. The molecular weight of purified enzyme was estimated to be 43.000 dalton by SDS-polyacrylamide gel electrophoresis and gel filteration column chromatography The enzyme activity was highest at 40t and PH 7.0 The enzyme activity was relatively high by $\beta$-mercaptoethanol but strongly inhibited by cysteine.

• Korean Journal of Microbiology
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• v.34 no.4
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• pp.219-224
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• 1998

The cyclic metabolism of poly(3-hydroxyhutyrate-co-3-hydroxyvalerate) synthesized from glucose by Alcaligenes sp. SH-69 in the presence or absence of new carbon substrate was investigated. In batch culture, the content and weight average molecular weight of the copolymer already stored in the cell decreased rapidly when there was no other carbon source available. After the depletion of carbon source, the amount of high molecular weight copolymer decreased more rapidly than that of low molecular weight copolymer, and as a result, average molecular weight distribution shifted to the lower value. The addition of a mixture of glucose and levulinic acid when the initial carbon substrate, glucose, was nearly depleted supported the continual increase in cell mass and the accumulation of poly(3HB-co-3HV) with high molar fraction of 3HV. However, solvent fractionation of the polymer with acetone revealed the degradation of pre-existing polyhydroxyalkanoale (PHA) in parallel with the synthesis of PHA from new carbon substrate. Even though PHAs obtained from each substrate alone were the copolymer of 3HB and 3HV, it was found that the polymer accumulated in the cells grown by sequential feeding was mainly physical mixture of two poly(3HB-co-3HV) copolymers containing different molar fractions of 3HV.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.357-366
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• 2017

Natural pigments are materials that express color and have been used in foods, cosmetics, medicine and so on. Since natural pigments are extracted from animals and plants, they are not uniform in size. Red pigments in particular are more lipophilic than other color pigments and tend to aggregate easily in aqueous solutions which make it difficult to reproduce the specific color due to size change. Found to be an allergen and the growing aversion for it to be used in foods, cochineal pigment, an animal pigment used for red pigments is being used less. In this study, red vegetable pigment lycopene extract and gardenia yellow was made uniform in size by ball-milling, then asymmetrical flow-field flow fractionation (AsFlFFF) and dynamic light scattering (DLS) were used to measure the size, and a color meter was used to confirm the color. Experimental results showed that the pigment particles were large in size and size distribution was wide before milling, but the size of the particles decreased and size distribution narrowed after milling. Color meter measurements showed that as the milling time increased, the size of the pigment particles decreased and the brightness, redness, and yellowness increased indicating a bright red color.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.99-103
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• 2006

Use of recycled fibers in papermaking has been increased for economical and environmental reasons. Recycled panels are major liber resources for brown grades and newsprints. Since the recycled fibers have disadvantageous properties as raw materials for papermaking it is of great importance to optimize the use of these recycled fibers. OCC (Old Corrugated Containers) is the major fiber source for linerboards and corrugating mediums that require diverse specification in strength properties. Many studies have been focused to overcome the problems of strength reduction of brown grades when recycled fibers are used as raw materials. The problem of strength loss for papers made from recycled fibers is closely associated with the increased amount of fines in recycled fibers and hornification of fibers. Fines contained in the recycled fiber resources cause problems not only in paper properties but also in process runnability. This shows that the optimal management and proper use of fines in recycling papermaking system are critical to get most benefits of using recycled fibers. In this study some approaches for optimal use of fiber fines in recycled paper mill have been investigated. Stock samples, prepared in the laboratory and obtained from a recycling plant were used. Fractionation of these samples was made using Sweco screen. And the effect of the addition of polyelectrolytes including cationic PAM and PEI on drainage and retention was evaluated. Different methods of polymer addition were compared to find the most effective ways of treating recycled fiber stocks with polyelectrolytes. Addition of polyelectrolytes to the short fiber fraction was most effective in retention and drainage. The influence of the charge and molecular weight of these two polymers has been examined and discussed.