Jiyeon Chun

Characterization of a 27 kDa fibrinolytic enzyme from Bacillus amyloliquefaciens CH51 isolated from cheonggukjang.

Bacillus amyloliquefancies CH51 isolated from cheonggukjang, a traditional Korean fermented soy food, has strong fibrinolytic activity and produces several fibrinolytic enzymes. Among four different growth media, tryptic soy broth was the best in terms of supporting cell growth and fibrinolytic activity of this strain. A protein with fibrinolytic activity was partially purified from the culture supernatant by CMSephadex and Phenyl Sepharose column chromatographies. Tandem mass spectrometric analysis showed that this protein is a homolog of AprE from B. subtilis and it was accordingly named AprE51. The optimum pH and temperature for partially purified AprE51 activity were 6.0 and 45 degrees , respectively. A gene encoding AprE51, aprE51, was cloned from B. amyloliquefaciens CH51 genomic DNA. The aprE51 gene was overexpressed in heterologous B. subtilis strains deficient in fibrinolytic activity using an E.colo-Bacillus Shuttle vector, pHY300PLK.

Zeatin Prevents Amyloid β-Induced Neurotoxicity and Scopolamine-Induced Cognitive Deficits

The antioxidative and protective effects of zeatin against amyloid beta-protein (Abeta)-induced neurotoxicity were investigated using PC12 cells. Zeatin showed antioxidative and cell protective effects against Abeta-induced neurotoxicity. In this study, we also evaluated the effect of zeatin on learning and memory capacity in vivo using ICR mice with amnesia induced by scopolamine (1 mg/kg of body weight). Zeatin, when administered to mice at 4.5 mg/kg of body weight, significantly ameliorated scopolamine-induced amnesia as measured in both the passive avoidance test and Y-maze test. Injecting mice with scopolamine impaired performance on the passive avoidance test (48 +/- 4.5% decrease) and on the Y-maze test (12 +/- 1.3% decrease). In contrast, mice treated with zeatin before scopolamine injections were protected from these changes (5-34% decrease in step-through latency; 1-4% decrease in alternation behavior). The present results suggest a possible chemopreventive role of zeatin in Alzheimers disease.

Chronic effect of ferulic acid from Pseudosasa japonica leaves on enhancing exercise activity in mice.

Ferulic acid derived from Pseudosasa japonica leaves, which possessed antioxidative potentials with DPPH‐ (54%) and ABTs‐ (65%) radical scavenging activities, and lipid‐peroxidation inhibitory activity (71%), was orally administered to mice for 12 days in order to investigate its effects on exercise endurance capacity and alterations of antioxidant defense systems. Exhaustive swimming time was increased in the ferulic acid‐supplemented group compared with the control group on days 6 and 12 (1.7‐ and 1.8‐fold, respectively). When the mice were exhaustively exercised for 2 consecutive days, a high decrease (53%) was shown in the control group, but no change was found in the ferulic acid‐treated group. The administration of ferulic acid significantly protected the depletion of enzymatic‐ and non enzymatic‐antioxidants due to exhaustive exercise. Also, lipid‐peroxidation levels decreased in the ferulic acid‐treated group compared with the non exercised‐ and control‐groups. These results suggest that ferulic acid from Pseudosasa japonica leaves has a chronic effect on endurance exercise capacity, which is attributed to its ability to ameliorate oxidative stress by improving antioxidant potentials. Copyright

Hydration and Pasting Properties of Oat (Avena sativa) Flour.

Three oat cultivars and one oat breeding line were evaluated for chemical, hydration and pasting properties. Protein, starch and β-glucan levels ranged 11.13∼14.37, 56.37∼64.86 and 3.44∼4.76%, respectively. The oat cultivars Daeyang and Seonyang contained higher β-glucan levels of 4.76 and 4.35%. The Daeyang variety had a higher water absorption index (WAI) of 2.83∼3.35 (g/g), but a lower water solubility index (WSI) of 8.67 ∼11.08%. Daeyang and Seonyang cultivars showed higher peak and trough viscosity, but lower breakdown and setback, indicating that they easily swell, and thus could possibly provide the desirable viscosity of an oat product. The β-glucan levels were correlated positively with WAI, peak and trough viscosity, and negatively to WSI, breakdown and setback viscosity.

Effect of Frozen Storage Temperature on the Quality of Premium Ice Cream

The market sales of premium ice cream have paralleled the growth in consumer desire for rich flavor and taste. Storage temperature is a major consideration in preserving the quality attributes of premium ice cream products for both the manufacturer and retailers during prolonged storage. We investigated the effect of storage temperature (−18℃, −30℃, −50℃, and −70℃) and storage times, up to 52 wk, on the quality attributes of premium ice cream. Quality attributes tested included ice crystal size, air cell size, melting resistance, and color. Ice crystal size increased from 40.3 μm to 100.1 μm after 52 wk of storage at −18℃. When ice cream samples were stored at −50℃ or −70℃, ice crystal size slightly increased from 40.3 μm to 57-58 μm. Initial air cell size increased from 37.1 μm to 87.7 μm after storage at −18℃ for 52 wk. However, for storage temperatures of −50℃ and −70℃, air cell size increased only slightly from 37.1 μm to 46-47 μm. Low storage temperature (−50℃ and −70℃) resulted in better melt resistance and minimized color changes in comparison to high temperature storage (−18℃ and −30℃). In our study, quality changes in premium ice cream were gradually minimized according to decrease in storage temperature up to−50℃. No significant beneficial effect of −70℃ storage was found in quality attributes. In the scope of our experiment, we recommend a storage temperature of −50℃ to preserve the quality attributes of premium ice cream.

Effect of Sub- and Super-critical Water Treatment on Physicochemical Properties of Porcine Skin

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-H2O, 300℃, 80 bar) treatment as well as super-critical water (Super-H2O, 400℃, 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℃, 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-H2O or Sub-H2O treatment. The free amino acid content was 57.18 mM and 30.13 mM after Sub-H2O and Super-H2O treatment, respectively. Determination of amino acid profile revealed that the content of Glu (22.5%) and Pro (30%) was higher after Super-H2O treatment than after Sub-H2O treatment, whereas the content of Gly (28%) and Ala (13.1%) was higher after Sub-H2O treatment. Super-H2O or Sub-H2O treatment affected the pH of PS, which changed from 7.29 (Raw) to 9.22 (after Sub-H2O treatment) and 9.49 (after Super-H2O treatment). Taken together, these results showed that Sub-H2O treatment was slightly more effective for hydrolysis than Super-H2O was. However, both Sub-H2O and Super-H2O treatments were effective processing methods for hydrolysis of PS collagen in a short time and can be regarded as a green chemistry technology.

Production of soy yogurt enriched with glyceollins

Soy milk was prepared from regular soybean (M1), soybean germinated for 3 days at 25°C (M2), and soybean germinated under fungal infection (M3). Rhizopus microsporus var. oligosporus ATCC 22959 was used as the elicitor for glyceollin production. Each soy milk was fermented with Streptococcus infantarius 12 and Weissella sp. 4 (1:5, v/v) for 12 h at 37°C. Significant induction of glyceollins was confirmed only in M3 soy milk and glyceollins maintained stably during 12 h fermentation period. The concentration of glyceollins in M3 yogurt was 2,400.4±83 and 2,525.2±158 μg/g dry matter (d.m.) at 0 and 12 h, respectively. The amount of daidzein was significantly higher in M3 yogurt (635.1±21) than that of M1 (417±11) and M2 (545±17 μg/g d.m.) yogurt in 12 h (p<0.05). M2 yogurt had the highest amount of genistein (695.3±17) followed by M3 (634.5±26) and M1 (612.5±14 μg/g d.m.) yogurt. M3 soy yogurt also showed the highest content of total phenolic compounds (5.37 mg/g) and antioxidant activity. The results indicated that functional soy yogurt can be prepared from soybean enriched with glyceollins.

Change of Multiple-Layered Phospholipid Vesicles Produced by Electrostatic Deposition of Polymers during Storage

Abstract In this study, 1 wt% lecithin (–), chitosan (+), and λ-carrageenan (–) were prepared to manufacture multiple-layered liposomes with optimal formulations developed in a previous study by using layer-by-layer electrostatic deposition. We observed their particle size, ζ-potential, sedimentation behavior, and microstructure for 6 weeks. Multiple-layered liposomes were quenched with calcein to evaluate stability in terms of factors such as encapsulation efficiency and released amount of calcein. The particle size of multi-layered liposomes increased with storage periods and the ζ-potential of multiple-layered liposomes gained a neutral charge. Interestingly, negatively charged layered liposomes were smaller than positively charged layered liposomes and showed a lower polydispersity index. Moreover, the ζ-potential did not apparently change compared to positively charged layered liposomes. For the calcein release study, multiple-layered liposomes significantly sustained quenched calcein more than that observed using non-layered liposomes. This study showed that it was possible to increase the thickness of the liposome surface and to manipulate its charge using chitosan and λ-carrageenan through electrostatic deposition. Results showed that manufacturing negatively charged multiple-layer (over 4-layer) liposomes with charged biopolymer improved the physicochemical stability of liposomes.

Thermal and functional characteristics of defatted bovine heart using supercritical CO2 and organic solvent: Thermal and functional properties of SC-CO2 and hexane-treated bovine heart

BACKGROUND Consumer demand for low-fat foods has been increasing as a result of attempts to reduce obesity and chronic diseases. Bovine heart was defatted using supercritical CO2 (SC-CO2 ) at different pressures together with solvent extraction to produce a protein-based functional ingredient for low-fat food products. Thermal and functional characteristics of control and defatted samples were compared. RESULTS Supercritical CO2 treatment at high pressure results in more removal of fat, producing a protein-rich defatted bovine heart (DBH). The differential scanning calorimeter (DSC) thermograms and SDS-PAGE bands for SC-CO2 -treated DBHs were similar to those of the control sample, indicating high protein stability and better functionality. Hexane-treated DBH showed no major thermal peaks and very diffuse bands in SDS-PAGE, indicating denaturation of proteins during solvent extraction. No denaturation of proteins in SC-CO2 -treated DBHs resulted in significantly higher water/oil absorption capacities (3320.00 and 2630.00 g kg-1 , respectively), total soluble solids (822.20 and 208.71 g kg-1 at pH 3.5 and 6.5, respectively), foaming capacities (149.37%), and emulsion activity (66.89%) than the hexane-treated DBH. CONCLUSION Supercritical CO2 treatment of DBH led to higher thermal stability and functional properties than the control and hexane-treated DBH. Defatted bovine heart using SC-CO2 can be a functional ingredient for various low-fat and high-protein food products for health-conscious consumers.

Validation of Pepsin-Assisted Extraction and Immunoaffinity-HPLC/DAD Analysis for Vitamin B12 in Seafood

한국은 삼면이 바다로 둘러 쌓여있어 연중 다양한 수산물이 식단에 활용되고 있기 때문에 수산물은 쇠고기나 돼지고기와 같은 육류 자원과 함께 한국 식단에서 비타민 B12 섭취를 위한 우수한 급원이 되고 있다. 식품 중의 비타민 B12는 단백질과 결합된 형태로 존재할 수 있으므로 국내 수산 자원의 비타민 B12 함량에 대한 신뢰도 있는 데이터베이스 구축을 위해서는 비타민 B12 추출법에 대한 검증이 필요하다. 따라서 본 연구에서는 매트릭스가 다른 수산물 4종(바지락, 꽃게, 고등어, 오징어)을 선정하여 pepsin을 이용한 비타민 B12 추출을 immunoaffinity column을 이용한 clean-up 및 HPLC/DAD 분석에 적용하는 분석법의 유효성을 검증하였다. 시료는 생물을 구입하여 가식 부위만 균질화한 다음 pepsin 처리 없이 추출된 자유 비타민 B12와 pepsin을 처리하여 결합된 비타민 B12를 포함한 총 비타민 B12 함량을 각각 분석하였으며, 이에 대한 분석법 검증(특이성, 민감성, 직선성, 정확성, 정밀성)을 수행하였다. 효소 처리 여부와 상관없이 특이적으로 cyanocobalamin을 분석할 수 있었으며 우수한 직선성(y=2008x－19.757, R²=0.9992)을 나타내었다. 검출한계(LOD)와 정량한계(LOQ)는 pepsin 무처리 시 각각 0.006과 0.061 μg/100 g을 나타내었으나 pepsin 처리 시 약 2배가 높은 0.015와 0.106 μg/100 g을 나타내었다. 인증참고물질 BCR-487(pig liver)을 분석한 회수율 측정에서 pepsin 처리가 99.4%, 무처리 추출이 96.3%로 효소 처리법이 다소 높은 회수율을 나타내었다. 정밀성 시험에서는 pepsin 무처리 추출의 반복성과 재현성이 각각 6.0과 10.5%, pepsin 처리 시 각각 9.4와 13.6%로 나타나 효소를 이용한 추출에서 정밀성이 더 높아지는 것으로 나타났다. 그러나 두 분석법 모두 AOAC에서 제안하는 수용 범위 수준을 충족하는 정확성과 정밀성을 나타내어 식품 중의 비타민 B12 분석에 적용 가능할 것으로 보인다. Pepsin 처리 추출법을 적용한 immunoaffinity-HPLC 분석법으로 4종 수산물(raw, wet basis)의 비타민 B12 함량을 분석한 결과, 바지락의 자유와 총 비타민 B12 함량은 각각 46.9와 55.2 μg/100 g으로 총 비타민 B12 함량이 유의적으로 높게 나타났으나(P<0.05), 꽃게와 오징어의 경우 각각 6.09~6.87 μg/100 g과 2.39~2.45 μg/100 g의 범위를 보이며 유의적인 차이를 나타내지 않았다. 이는 바지락과 고등어의 경우 총 비타민 B12 함량중에서 각각 약 18%와 20%가 단백질과 결합된 상태로 존재하는 것을 의미하며 이는 pepsin과 같은 효소를 이용한 추출법이 필요하다는 것을 가리킨다 하겠다. 또한, 본 연구의 LOD와 LOQ 결과는 pepsin 처리를 이용한 immunoaffinity-HPLC/DAD 분석법이 식품 중에 낮은 수준으로 존재하는 비타민 B12를 분석하는 데 적용 가능한 분석법임을 보여준다. Pepsin을 이용한 비타민 B12 분석은 정밀성과 정확성이 수용 범위 수준이기는 하지만 무처리 분석보다는 높기 때문에 다양한 수산 자원의 매트릭스에 따른 이들의 적용여부는 보다 구체적인 접근 방법을 검토해보는 것이 필요하다 생각된다.