• KSBB Journal
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• v.19 no.4
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• pp.327-330
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• 2004

An inducible expression system of poly[(R)-3-hydroxybutyrate] (PHB) depolymerization was established in metabolically engineered Escherichia coli with the PHB biosynthesis genes. The Ralstonia eutropha PHB depolymerase gene was cloned in a vector system containing the PHB biosynthesis genes and expressed under inducible promoter. Recombinant E. coli harboring the PHB biosynthesis genes and depolymerase gene was first cultured for the accumulation of PHB, and then the depolymerase was expressed resulting in the degradation of accumulated PHB into (R)-3-hydroxybutyric acid (R3HB). R3HB could be produced with the concentration of 7.6 g/L in flask culture. Two different PHB biosynthesis genes from Alcaligenes latus and R. eutropha were compared for the production of R3HB. This strategy can be used for the production of enantiomerically pure (R)-hydroxycarboxylic acids with high concentration.

• Food Science and Biotechnology
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• v.18 no.4
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• pp.872-877
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• 2009

By-products of marine organisms including salmon, skate, flatfish, and yellow goosefish were investigated to search for new source of chondroitin sulfate (CS). Agarose gel electrophoresis with chondroitinase depolymerization showed that purified chondroitin sulfate did not contain any other glycosaminoglycans. 1H-nuclear magnetic resonance (NMR) spectra were acquired to confirm the structure and purity. The average molecular weight ranging from 22 to 64 kDa was determined by high performance size exclusion chromatography. Disaccharide compositions and purities were determined by strong anion exchange-high performance liquid chromatography (SAX-HPLC) after chondroitinase ABC depolymerization. SAX-HPLC data exhibited that the purity was from $81.7{\pm}1.3$ to $114.2{\pm}2.5%$ and the yield was from 1.3 to 12.5%. All analytical results indicate that salmon cartilage, skate cartilage, and yellow goosefish bone could be promising sources of CS to substitute shark cartilage CS in commercial neutraceuticals.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.61-64
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• 1998

We have investigated the effects of ultraviolet (UV) light irradiation condition and imidization temperature for the generation of pretilt angle in nematic liquid crystal (NLC) on the two kinds of the polyimide (PI) surfaces. High pretilt angle of NLC is generated with oblique p-polarized UV light irradiation of 30$^{\circ}$ on PI surface for 20 min. Also, the high pretilt angle of NLC is generated with oblique p-polarized UV light irradiation of 10-30$^{\circ}$ on PI surface at 20min. The pretilt angle of NLC decreases with increasing the imidization temperature on all rubbed PI surfaces ; the pretilt angle of NLC with oblique p-polarized UV light irradiation of 30$^{\circ}$on PI surface decreases with increasing the imidization temperature. The high pretilt angle of NLC is observed due to high photo-depolymerization reaction by low surface energy at low imidization temperature. We suggest that the pretilt angle of NLC is strongly attributed to the photo-depolymerization reaction with the UV light irradiation condition and imidization temperature.

• Journal of Environmental Health Sciences
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• v.28 no.2
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• pp.41-49
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• 2002

Resource recovery and recycling of materials and products including polyurethanes are viewed as a necessity in today's society. The problems of recycling polyurethane wastes has major technological, economic and ecological significance because polyurethane itself is relatively expensive and its disposal by burning is also costly. In general, the recycling methods for polyurethane could be classified as mechanical, chemical and physical. In the chemical recycling method, there ate hydrolysis, glycolysis, pyrolysis and aminolysis. This study was carried out glycolysis using new method such as sonication and catalyzed reaction. There are kinds of recycled polyols were produced by current method(glycolysis) but, this study were with catalyzed reaction and sonication as decomposers and the chemical properties were analyzed. The reaction results in the formation of polyester urethane diols and then the OH value which is determined by the quantity of diol used for the glycolysis conditions. The glycolysis rates by sonication and catalyzed reaction for the various glycols, increased as: PPG

• Journal of the Korean Chemical Society
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• v.17 no.6
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• pp.450-454
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• 1973

The afterpolymerization and depolymerization of poly-${\varepsilon}$-caproamide in solid state have been studied under two different reaction conditions, nitrogen flow and sealed state. The degree of polymerization ($\bar{P}$) of nylon 6 increased with the increase in reaction time and temperature, and then reacted finally an equilibrium. In the presence of oxygen, $\bar{P}$ decreased by increasing the reaction time due to the oxidation reaction. Under certain reaction condition, the change of $\bar{P}$ for different initial degree of polymerization ($\bar{P}_0$) tendered toward unity in equilibrium.

• YAKHAK HOEJI
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• v.42 no.1
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• pp.31-38
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• 1998

Dextran-5-(4-ethoxycarbonylphenylazo)salicylic acid ester(Dextran-5-ESA) was synthesized as a potential colon-specific prodrug of 5-aminosalicylic acid (5-ASA). No free 5-(4-eth oxycarbonylphenylazo) salicylic acid (5-ESA) was detected when the chemical stability of dextran-5-ESA was tested at pH 1.2, or pH 6.8 bath solution, Effects of the degree of substitution (DS) and molecular weight of dextran on the depolymerization by dextranase was investigated. Depolymerization(%) decreased with increasing DS, and was not affected by M.W. of dextran. The extent of prodrug conversion after incubation in the contents of various G.I. Tract segments of rats was evaluated. 5-ASA was released in the cecal contents, but not in the contents of proximal small intestine (PSI) or distal small intestine (DSI). No significant prodrug conversion was observed in the cecal contents of rats pretreated with kanamycin sulfate, which indicated that microbial enzymes were responsible for the cleavage of the prodrug.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.124-134
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• 2016

The main goal of this study was to investigate biomodification mechanism of lignin by white rot fungus, Abortiporus biennis, and to depolymerize ethanol organosolv lignin for industrial application. In nitrogen-limited culture, A. biennis polymerized mainly lignin showing a rapid increase of molecular weight and structural changes depending on incubation days. At the initial incubation days, cleavage of ether bonds increased phenolic OH content, while the results were contrary in of the later part of the culture. Based on these results, ascorbic acid as a reducing agent was used to induce depolymerization of lignin during cultivation with white rot fungus. As a result, the degree of increase of average molecular weight of lignin was significantly declined when compared with those of the ascorbic acid free-experiment, although the molecular weight of fungus treated sample slightly increased than that of control. Furthermore, lignin derived oligomers in culture medium were depolymerized with the addition of ascorbic acid, showing that the average molecular weight was 381 Da, and phenolic OH content was 38.63%. These depolymerized lignin oligomers were considered to be applicable for industrial utilization of lignin. In conclusion, A. biennis led to the polymerization of lignin during biomodification period. The addition of ascorbic acid had a positive effect on the depolymerization and increase of phenolic OH content of lignin oligomers in medium.

• Clean Technology
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• v.28 no.3
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• pp.232-237
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• 2022

Biorefineries, in which renewable resources are utilized, are an eco-friendly alternative based on biomass feedstocks. Alginic acid, a major component of brown algae, which is a type of marine biomass, is widely used in various industries and can be converted into value-added chemicals such as sugars, sugar alcohols, furans, and organic acids via catalytic hydrothermal decomposition under certain conditions. In this study, ruthenium-supported activated carbon and magnesium oxide were mixed and applied to the depolymerization of alginic acid in a batch reactor. The addition of magnesium oxide as a basic promoter had a strong influence on product distribution. In this heterogeneous catalytic system, the separation and purification processes are also simplified. After the reaction, low molecular weight alcohols and organic acids with 5 or fewer carbons were produced. Specifically, under the optimal reaction conditions of 30 mL of 1 wt% alginic acid aqueous solution, 100 mg of ruthenium-supported activated carbon, 100 mg of magnesium oxide, 210 ℃ of reaction temperature, and 1 h of reaction time, total carbon yields of 29.8% for alcohols and 43.8% for a liquid product were obtained. Hence, it is suggested that this catalytic system results in the enhanced hydrogenolysis of alginic acid to value-added chemicals.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.579-582
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• 2000

Enantiomerically pure hydroxycarboxylic acids have great potential as chiral building blocks in fine chemicals due to their easily modificable two functional groups. Microbial polyhydroxyalkanoates (PHAs) can have more than one hundred of hydroxycarboxylic acids as monomeric constituents by growing cells under various conditions. All of the monomeric constituents are enantiomerically pure in (R)-conformation if there is a chiral center. Therefore, efficient production of enantiomerically pure hydroxycarboxylic acids by degrading PHAs is possible. In this presentation, we report on the development of a novel method for the preparation of (R)-hydroxybutyric acid by in vivo depolymerization of Polyhydroxybutyrae.

• Textile Coloration and Finishing
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• v.10 no.1
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• pp.20-24
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• 1998

Oligomeric extracts of poly(ethylene terephthalate-co-ethylene isophthalate)s [(PET/EI] are analyzed by high performance liquid chromatography(HPLC) and nuclear magnetic resonance spectroscopy (NMR). Existence of separated peaks for small cyclics of trimer and tetramer gives the existence of structural isomeric forms. NMR confirms that cyclization of PET/EI occurs more easily at the site of isophthaloyl unit.