• Journal of Adhesion and Interface
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• v.4 no.1
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• pp.18-27
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• 2003

Interfacial properties and microfailure degradation mechanisms of the oxygen-plasma treated biodegradable poly(p-dioxanone) (PPDO) fiber/poly(L-lactide) (PLLA)composites were investigated for the orthopedic applications as implant materials using micromechanical technique and surface wettability measurement. PPDO fiber reinforced PLLA composite can provide good mechanical performance for long hydrolysis time. The degree of degradation for PPDO fiber and PLLA matrix was measured by thermal analysis and optical observation. IFSS and work of adhesion, $W_a$ between PPDO fiber and PLLA matrix showed the maximum at the plasma treatment time, at 60 seconds. Work of adhesion was lineally proportional to the IFSS. PPDO fiber showed ductile microfailure modes at We initial state, whereas brittle microfailure modes appeared with elapsing hydrolysis time. Interfacial properties and microfailure degradation mechanisms can be important factors to control bioabsorbable composites performance because IFSS changes with hydrolytic degradation.

• Journal of Adhesion and Interface
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• v.15 no.2
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• pp.69-76
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• 2014

Two kinds of epoxy-functionalized alkoxysilane (EAS) compounds (EAS-MS and EAS-ES) were successfully synthesized through the reaction between epoxy resin (YD-128) and aminopropyl trimethoxysilane (APTMS) or aminopropyl triethoxysilane (APTES). By the hydrolysis-polycondensation reaction of EAS compounds with 3-Glycidyloxypropyl trimethoxysilane (GPTMS) and Tetraethyl orthosilicate (TEOS), silica/epoxy nanohybrids could be prepared at various compositions of EAS to GPTMS/TEOS. Prepared nanohybrids were yellow transparent and miscible with various organic solvents. By the reaction silica/epoxy nanohybrids with curing agents (TETA or acrylic acid), cured hybrids films could be obtained. These cured films showed higher thermal stability and mechanical property compared to cured neat epoxy resin. TEM and AFM images showed formation of nano-sized silica nanoparticles within cured hybrid films.

• Microbiology and Biotechnology Letters
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• v.15 no.2
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• pp.122-128
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• 1987

Lipases from Candida rogosa and Rhizopus arrhizus were immobilized by entrapment with photo-crosslinkable resin prepolymer for the study of fat splitting and interesterification in isooctane-two phase system. Dioctylsulfosuccinate was selected as the most suitable surfactant during the immobilization. Lipase entrapped with hydrophobic photo-crosslinkable resin prepolymer(ENTP-3000) exhibited the highest activity, whereas lipase entrapped with hydrophilic gel(ENT-4000) was more stable in organic solvent. As the degree of hydrophobicity of the immobilization matrix was increased, Vm(app) of the lipase entrapped was increased, but Km(app) was approximately constant. While the optimum pH of the lipases entrapped on hydrophilic gel (ENT-4000) were around pH 7.0 for Candida lipase and Rhizopus lipase, the reaction rate of the lipases entrapped on hydrophobic gel were less dependent on pH variations for short reaction time. However, for longer reaction time, the lipnses from C. rugosa and R. arrhizus entrapped on hydrophobic gel yielded maximum rate at pH 6.0 and 6.5, respectively, Entrapment method endowed the lipase with thermal stability.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.2
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• pp.89-97
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• 2007

In this study, thermalpretreatment was used to solubilize organic matter contained in sewage sludge before acid fermentation. By thermal pretreatment, solubilization of particulate CODcr, carbohydrate and protein increased. By thermal treatment at $120^{\circ}C$ for 30 minutes, CODcr solubilization efficiency of the primary sludge reached 8.3%. Meanwhile, for the secondary sludge, CODcr solubilization efficiency reached 16.5% because of high solubilization ratio of protein under the same pretreatment conditon. The results of anaerobic biodegradability test showed that both VFAs conversion ratio and hydrolysis rate of organic compounds in sewage sludge were improved by thermal pretreatment. Meanwhile, the optimum thermal pretreatment condition was varied with composition of organic compounds in sludge. In this study, the optimun thermal pretreatment condition of the primary sludge, containing high concentration of carbohydrate, was $80^{\circ}C$ for 30 minutes. Meanwhile, for the secondary sludge, mainly composed of protein, the sludge treated at $120^{\circ}C$ for 30 minutes showed the effective organic removal and VFAs production.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.7
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• pp.746-752
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• 2005

In this study, the effect of reaction parameters including reaction temperature, time, and pressure on sludge degradation and conversion to intermediates such as organic acids were investigated at low critical wet air oxidation(LC-WAO) conditions. Degradation pathways and a modified kinetic model in LC-WAO were proposed and the kinetics model predictions were compared with experimental data under various conditions. Results in the batch experiments showed that reaction temperature directly affected the thermal hydrolysis reaction rather than oxidation reaction. The efficiencies of sludge degradation and organic acid formation increased with the increase of the reaction temperature and time. The removal of SS at $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 10 min of reaction time were 52.6%, 68.3%, 72.6%, and 74.4%, respectively, indicating that most organic suspended solids were liquified at early stage of reaction. At $180^{\circ}C$, $200^{\circ}C$, $220^{\circ}C$ and $240^{\circ}C$ of reaction temperatures and 40 min of reaction time, the amounts of organic acids formed from 1 g of sludge were 93.5 mg/g SS, 116.4 mg/g SS, 113.6 mg/g SS, and 123.8 mg/g SS, respectively, and the amounts of acetic acid from 1 g of sludge were 24.5 mg/g SS, 65.5 mg/g SS, 88.1 mg/g SS, and 121.5 mg/g SS, respectively. This suggested that the formation of sludge to organic acids as well as the conversion of organic acids to acetic acid increased with reaction temperature. Based on the experimental results, a modified kinetic model was suggested for the liquefaction reaction of sludge and the formation of organic acids. The kinetic model predicted an increase in kinetic parameters $k_1$ (liquefaction of organic compounds), $k_2$ (formation of organic acids to intermediate), $k_3$ (final degradation of intermediate), and $k_4$ (final degradation of organic acids) with reaction temperature. This indicated that the liquefaction of organic solid materials and the formation of organic acids increase according to reaction temperature. The calculated activation energy for reaction kinetic constants were 20.7 kJ/mol, 12.3 kJ/mol, 28.4 kJ/mol, and 54.4 kJ/mol, respectively, leading to a conclusion that not thermal hydrolysis but oxidation reaction is the rate-limiting step.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.2
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• pp.109-124
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• 1990

A rapid processing method for fish sauce of high quality stability and favorable flavor was investigated using mackerel waste as starting material. The chopped waste was homogenized with water and hydrolyzed by commercial proteolytic enzymes such as Complex enzyme-2000($2.18\cdot10^4$ U/g solid, Pacific Chem. Co.) and Alcalase ($1.94\cdot10^4$ U/g solid, Novo) in a cylindrical vessel with 4 baffles and 6-bladed turbine impeller. Optimal pH and temperature for the hydrolysis with Complex enzyme-2000 were 8.0 and $50^{\circ}C$, and those with Alcalase were 9.0 and $55^{\circ}C$. In both cases, the reasonabe amount of added water and enzyme concentration based on the waste weight were $40\%,\;3\%$ and hydrolyzing time was 100 min. Thermal treatment of the hydrolysate with $6\%$ of invert sugar for 2 hours at $90^{\circ}C$ was adequated to inactivation of the enzymes and pasteurization of the hydrolysate. Flavor, taste and color of the hydrolysate were improved during the thermal treatment in which the browning reaction products might participate and result in antioxidative and bactericidal effects. Combined use of $0.005\%$ of Caryophylli flos with $6\%$ of invert sugar was also effective for the improvement of taste. Yield of the fish sauce based on the total nitrogen of the raw waste was $93.7\~94.9\%$, and $87.6\~87.9\%$ of the total nitrogen in the fish sauce was in the from of amino nitrogen. The pH, salinity and histamine content of the fish sauce prepared with $15\%$ of table salt were $6.1\~6.2$, $14.0\~14.5\%$ and less than $10mg\%$, respectively. The fish sauce was stable on bacterial growth during the storage of 60 days at $26\pm3^{\circ}C$ and the quality was also maintained.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.1
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• pp.10-19
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• 1986

A study on the rapid fermentation of fish sauce has been carried out for effective utilization of sardine. The frozen sardine was thawed at room temperature, chopped, homogenized with equal amount of water and then hydrolyzed by addition of commercial proteolytic enzymes such as bromelain, papaya protease, ficin and a enzyme mixture under different conditions of hydrolysis. The effect of wheat gluten for masking fishy odor and color development during thermal treatment were also tested. The reaction mixture was heated for 30 minutes at $100^{\circ}C$ for enzyme inactivation, pasteurization and color development and then centrifuged for 20 minutes at 4,000 rpm. Finally, table salt and benzoic acid were added for bacteriostatic effect. The results were summarized as follows ; 1. The hydrolyzing temperature, time, pH and the concentration of enzymes based on the weight of whole sardine for optimal hydrolysis were as follows: autolysis, $52.5^{\circ}C$, 4 hours, pH 8.0: with $0.25\%$ bromelain, $52.5^{\circ}C$, 4 hours, pH 6.6 :with $0.25\%$ ficin, $52.5^{\circ}C$, 4 hours, pH 6.8: with $0.3\%$ papaya protease, $52.5^{\circ}C$, 4 hours, pH 6.6: with $6\%$ enzyme mixture, $52.5^{\circ}C$, 4 hours, pH 6.9, respectively. But pH control was not much beneficial in increasing yield. 2. The hydrolytic reaction of chopped sardine with proteolytic enzymes could be interpreted as a first order reaction that devided into 2 periods with different reaction rate constsnts. $Q_{10}$ values of the first period prior to 4 hours were 1.23 to 1.31, and those of post 4 hours were 1.25 to 1.55. The corresponding activation energies were $1.81{\times}10^4\;to\;2.34{\times}10^4\;kJ/kmol$ and $1.92{\times}10^4\;to\;3.77{\times}10^4\;kJ/kmol$, respectively. 3. The reasonable amount of $75\%$ vital wheat gluten for addition was $9\%$ of chopped sardine. 4. The dark brown color was mainly developed during the thermal treatment for 30 minutes at $100^{\circ}C$ and not changed during storage.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1192-1203
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• 1996

$Al_2O_3-TiO_2$ composite oxide adsorbents which could be applied in high-temperature water were prepared by hydrolysis of aluminum and titanium alkoxide. The prepared adsorbents were calcined at $600{\sim}1400^{\circ}C$ and in order to investigate the various properties - the transition of crystals, thermal properties, and specific surface area, X-ray diffractometry, thermal analysis, FT-IR, SEM and BET method were employed. And the $Co^{2+}$ adsorption characteristics of these adsorbents in high-temperature water were investigated by batch adsorption experiment in a stirred autoclave. Since the adsorption of $Co^{2+}$ on the $Al_2O_3-TiO_2$ adsorbents was irreversible endothermic in the temperature range of $150{\sim}250^{\circ}C$, the standard enthalpy changes of 26, 43, and 80 mol% of $TiO_2$ on $Al_2O_3$ were in the range of $16.5{\sim}26.0kJ{\cdot}mol^{-1}$. The adsorbent of 26 mol% of $TiO_2$ on $Al_2O_3$ which was calcined at $600^{\circ}C$ for 2 hours showed the adsorption amount of $0.1674meq{\cdot}g^{-1}$ in the high temperature water at $250^{\circ}C$.

• Microbiology and Biotechnology Letters
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• v.49 no.1
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• pp.88-94
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• 2021

The seaweed, Gracilaria verrucosa (red seaweed) was fermented to produce bioethanol. Optimal thermal acid hydrolysis conditions were determined as 200 mM H₂SO₄ and 10% (w/v) seaweed slurry at 130℃ for 60 min yielding 47.5% of pretreatment efficiency (E_p). After the thermal acid hydrolysis, enzymatic saccharification was carried out with 16 U/ml Viscozyme L, Cellic CTec2 or mixture of Viscozyme L and Cellic CTec2 to G. verrucosa hydrolysates. Enzymatic saccharifications with Viscozyme, Cellic CTec2 or mixture of those yielded 7.3 g/l glucose with efficiency of saccharification, E_s = 34.9%, 11.6 g/l glucose with E_s = 64.4% and the mixture of those 9.6 g/l glucose with E_s = 56.6%, respectively. Therefore, based on the E_s value, Cellic CTec2 was selected for the optimal enzyme for enzymatic saccharification of G. verrucosa hydrolysate. The ethanol productions with non-adapted S. cerevisiae CEN-PK2 (wild type) and S. cerevisiae CEN-PK2 with adaptive evolution to galactose produced 8.5 g/l ethanol with Y_EtOH = 0.19 and 21.5 g/l ethanol with Y_EtOH = 0.50 at 144 h, respectively. From these results, the ethanol production by S. cerevisiae with adaptive evolution showed high concentration of ethanol production using G. verrucosa as a substrate.

• Food Science of Animal Resources
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• v.35 no.1
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• pp.35-40
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• 2015

Super- and sub-critical water treatments have been of interest as novel methods for protein hydrolysis. In the present study, we studied the effect of sub-critical water (Sub-$H_2O$, $300^{\circ}C$, 80 bar) treatment as well as super-critical water (Super-$H_2O$, $400^{\circ}C$, 280 bar) treatment on the physicochemical properties of porcine skin (PS), which has abundant collagen. Porcine skin was subjected to pre-thermal treatment by immersion in water at $70^{\circ}C$, and then treated with sub- or super-critical water. Physicochemical properties of the hydrolysates, such as molecular weight distribution, free amino acid content, amino acid profile, pH, color, and water content were determined. For the molecular weight distribution analysis, 1 kDa hydrolyzed porcine skin (H-PS) was produced by Super-$H_2O$ or Sub-$H_2O$ treatment. The free amino acid content was 57.18 mM and 30.13 mM after Sub-$H_2O$ and Super-$H_2O$ treatment, respectively. Determination of amino acid profile revealed that the content of Glu (22.5%) and Pro (30%) was higher after Super-$H_2O$ treatment than after Sub-$H_2O$ treatment, whereas the content of Gly (28%) and Ala (13.1%) was higher after Sub-$H_2O$ treatment. Super-$H_2O$ or Sub-$H_2O$ treatment affected the pH of PS, which changed from 7.29 (Raw) to 9.22 (after Sub-$H_2O$ treatment) and 9.49 (after Super-$H_2O$ treatment). Taken together, these results showed that Sub-$H_2O$ treatment was slightly more effective for hydrolysis than Super-$H_2O$ was. However, both Sub-$H_2O$ and Super-$H_2O$ treatments were effective processing methods for hydrolysis of PS collagen in a short time and can be regarded as a green chemistry technology.