Powder preparation for a shell mold using a new coating process

A new coating process in the powder preparation for a shell mold has been developed to increase the fracture strength of the shell mold. It is due to the homogeneous formation of a glass phase on the starting particles and the increase in the glassification efficiency by the reduction in the loss of inorganic precursors. The inorganic binder system used for the new coating process is composed of tetraethyl orthosilicate (TEOS) and sodium methoxide (NaOMe) as the silica (SiO₂) and sodium oxide (Na₂O) precursors, respectively. Three different coating processes are employed for the powder preparation with a high glassification efficiency. In process I, the starting particles are coated with NaOMe, and then TEOS are coated on the particles treated with NaOMe. Process II is the reverse sequence of process I. Process III involves coating of the particles with a mixture of TEOS and NaOMe. The particles coated with an individual or mixture precursor were fixed with an organic binder and then heated at 1000 °C for 1 h. Molds prepared through the new coating processes, especially process III, show a higher fracture strength value compared with that of the conventional convert mold process, which may be caused by the increase in the glassification efficiency of the precursors. Powder prepared by process III shows a more uniform coating of the glass phase than those by other processes, resulting from an enhancement in the phase mixing between SiO₂ and NaOH molecules.     

Purification and Characterization of a Ginsenoside Rb1-Hydrolyzing ��-Glucosidase from Aspergillus niger KCCM 11239

Rb₁-hydrolyzing β-glucosidase from Aspergillus niger KCCM 11239 was studied to develop a bioconversion process for minor ginsenosides. The specific activity of the purified enzyme was 46.5 times greater than that of the crude enzyme. The molecular weight of the native enzyme was estimated to be approximately 123 kDa. The optimal pH of the purified enzyme was pH 4.0, and the enzyme proved highly stable over a pH range of 5.0–10.0. The optimal temperature was 70 °C, and the enzyme became unstable at temperatures above 60 °C. The enzyme was inhibited by Cu²⁺, Mg²⁺, Co²⁺, and acetic acid (10 mM). In the specificity tests, the enzyme was found to be active against ginsenoside Rb₁, but showed very low levels of activity against Rb₂, Rc, Rd, Re, and Rg₁. The enzyme hydrolyzed the 20-C,β-(1→6)-glucoside of ginsenoside Rb₁ to generate ginsenoside Rd and Rg₃, and hydrolyzed 3-C,β-(1→2)-glucoside to generate F₂. The properties of the enzyme indicate that it could be a useful tool in biotransformation applications in the ginseng industry, as well as in the development of novel drug compounds.     

日帝强占时期首尔的都市公园探析

位于朝鲜半岛中心的首尔是依照风水理论予以选址,并根据儒教理念进行都市空间规划的,至1897年大韩帝国建立之前没有很大改变。但开港以后,随着帝国主义及殖民主义对朝鲜半岛的影响,首尔发生了剧烈的变化,原有的空间秩序得以重新构筑首尔属于盆地地形,其近郊有丰富的山麓及溪谷,这些地方为市民提供了良好的游乐条件。因而西方近代都市的公园并不是必须具备的。随着1876年的开港,有关公园的情报及用语传入以后,诞生了近代公园,游览公园成为了都市人日常生活的一部分。特别是1920～1930年代首尔的都市公园,充分地实现了其功效。以清溪川为界,南村是以本町为中心的日本人的生活舞台,北村的钟路则是朝鲜人的街道。南山公园是位于南村居住地的日本人经常光顾的近邻公园,而塔洞公园则发挥了在钟路中心吸引众多民众的都心公园功能,其内涵却包含了殖民统治的优越性及为了合理化而精心实施的战略。     

Antioxidative and anti-inflammatory activities of Citrus unshiu peel extracts using a combined process of subcritical water extraction and acid hydrolysis

Antioxidant and in vitro anti-inflammatory activities of citrus (Citrus unshiu) peel extracts and their acid hydrolysates were evaluated. Citrus peel extracts were extracted by subcritical water, hot water, and ethanol. Subcritical water extraction led to extract more phenolic compounds than hot water or ethanol extraction. Acid hydrolysis more than doubled the extracts’ total phenolics and flavonoids. Acid hydrolysates showed greater DPPH-radical scavenging activities and antioxidant activities, as assayed by β-carotene bleaching and ferric thiocyanate, than the initial extracts. Anti-inflammatory activities of citrus peel extracts and hydrolysates, determined by the inhibition of hyaluronidase activity, showed that the inhibition activities of hot water and ethanol extracts increased from 2.1 and 1.8% to 37.0 and 18.5%, respectively, upon acid hydrolysis; however, the anti-inflammatory activity of the subcritical water extract was not improved. These results indicated that acid hydrolysis of citrus peel extracts regardless of their extraction methods improved the antioxidative and anti-inflammatory activities.     

Enhancement of the cytotoxicities and antioxidative activities of white ginseng extract by hydrolysis under mild acidic conditions

White ginseng extract (WGE) was hydrolyzed with organic acids to increase the yield of ginsenoside Rg₃ which has high bio-functional activities. The condition of hydrolysis by citric acid was studied to maximize a production of ginsenoside Rg₃. The total content of ginsenoside Rg₃ in WGE treated with 10% citric acid at 110°C for 1 h was 10-folds greater than that of commercial extract. The antitumor and antioxidant activities of WGE and the acid-hydrolysates were evaluated via an MTT assay and the DPPH method, respectively. At 1.0 mg/mL, hydrolysates inhibited the proliferation of AGS and Hep-2 cells by more than 90%, but did not inhibit their growth. It suggests that citric acid hydrolysis enhances the content of Rg₃. In addition, the acid hydrolysates evidenced a free radical scavenging activity of 80% at a concentration of 4.0 mg/mL, while WGE exhibited only a 49% free radical scavenging activity at the same concentration.     

Antimicrobial activity of acid-hydrolyzed Citrus unshiu peel extract in milk

Citrus fruit (Citrus unshiu) peels were extracted with hot water and then acid-hydrolyzed using hydrochloric acid. Antimicrobial activities of acid-hydrolyzed Citrus unshiu peel extract were evaluated against pathogenic bacteria, including Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes. Antilisterial effect was also determined by adding extracts at 1, 2, and 4% to whole, low-fat, and skim milk. The cell numbers of B. cereus, Staph. aureus, and L. monocytogenes cultures treated with acid-hydrolyzed extract for 12 h at 35°C were reduced from about 8 log cfu/mL to <1 log cfu/mL. Bacillus cereus was more sensitive to acid-hydrolyzed Citrus unshiu peel extract than were the other bacteria. The addition of 4% acid-hydrolyzed Citrus unshiu extracts to all types of milk inhibited the growth of L. monocytogenes within 1 d of storage at 4°C. The results indicated that Citrus unshiu peel extracts, after acid hydrolysis, effectively inhibited the growth of pathogenic bacteria. These findings indicate that acid hydrolysis of Citrus unshiu peel facilitates its use as a natural antimicrobial agent for food products.     

Synthesis of hollow and mesoporous polycaprolactone nanocapsules

New polycaprolactone (PCL) nanocapsules with a hollow core and mesoporous shell have been synthesized. The PCL nanocapsules have an average size of about 100 nm and a mesopores shell of about 20 nm. The size of the mesopores on the shell is about 4 nm. Fluorescent dye Rhodamin 6G was loaded into the nanocapsules to demonstrate the mesoporous structure of the capsules and their ability to load small molecules. The nanocapsules with such a structure can be used in many areas for various applications such as drug and gene delivery.     

Robust size control of bovine serum albumin (BSA) nanoparticles by intermittent addition of a desolvating agent and the particle formation mechanism

In polymeric nanoparticle preparation, despite similar conditions, large fluctuations in particle size distributions are usually observed. Herein, we demonstrate that the intermittent addition of a desolvating agent can improve reproducibility in the preparation of polymeric bovine serum albumin (BSA) nanoparticles. Using this modification, BSA nanoparticles of controlled size can be manufactured with narrow particle size distributions. In our study, ethanol as a desolvating agent was added intermittently to 1% BSA solutions at different pHs with stirring at 700 rpm. The effect of the preparation parameters on size and optical density of the fabricated nanoparticles were studied. The average particles sizes of BSA nanoparticles prepared at pH values of 6, 7 and 9 were approximately 100, 200 and 300 nm, respectively. As ethanol addition increased, desolvation of BSA molecules resulted in formation of loose-structured particles with pH-dependent size. Beyond that, only particle density increased, but size remained unchanged with further addition of ethanol. Consistently uniform particle size distribution was achieved by adding ethanol intermittently.