Yeung-Joon Choi

Angiotensin I-converting enzyme inhibitor derived from cross-linked oyster protein.

Following cross-linking by microbial transglutaminase, modified oyster proteins were hydrolyzed to improve inhibitory activity against angiotensin-converting enzyme (ACE) inhibitory activity with the use of a single protease, or a combination of six proteases. The oyster hydrolysate with the lowest 50% ACE inhibitory concentration (IC50) of 0.40 mg/mL was obtained by two-step hydrolysis of the cross-linked oyster protein using Protamex and Neutrase. Five ACE inhibitory peptides were purified from the oyster hydrolysate using a multistep chromatographic procedure comprised of ion-exchange, size exclusion, and reversed-phase liquid chromatography. Their sequences were identified as TAY, VK, KY, FYN, and YA, using automated Edman degradation and mass spectrometry. These peptides were synthesized, and their IC50 values were measured to be 16.7, 29.0, 51.5, 68.2, and 93.9 μM, respectively. Toxicity of the peptides on the HepG2 cell line was not detected. The oyster hydrolysate also significantly decreased the systolic blood pressure of spontaneously hypertensive rats (SHR). The antihypertensive effect of the oyster hydrolysate on SHR was rapid and long-lasting, compared to commercially obtained sardine hydrolysate. These results suggest that the oyster hydrolysate could be a source of effective nutraceuticals against hypertension.

Co-expression of nerve growth factor and p75NGFR in the inferior alveolar nerve after mandibular distraction osteogenesis

During mandibular distraction osteogenesis (DO), the inferior alveolar nerve (IAN) is damaged during distractor activation, but spontaneously recovers during consolidation. Although many neurotrophic factors are known to play critical roles, there have been few studies on the mechanism of peripheral nerve recovery after DO. The aim of this study was to observe the expression pattern of p75NGFR (low-affinity receptor of NGF) and to detect autocrine growth activity in IANs following mandibular DO. Unilateral mandibular distractions (0.5mm each, twice per day for 10 days) were conducted on eight mongrel dogs. Two each were killed at 7, 14, 28 and 56 days after completing distraction. The distracted IAN and contralateral control nerve were harvested. Immunohistochemical staining was performed to determine p75NGFR expression, and double immunofluorescent staining to detect NGF and p75NGFR co-expression. Levels of p75NGFR expression were found to be significantly elevated at 7 and 14 days in Schwann cells located in the outer layer of axon, but were almost undetectable at 28 and 56 days. In double immunofluorescent images, the co-expression of NGF and p75NGFR was also detected at 7 and 14 days. p75NGFR plays an important role in remyelination due to its abundant expression in Schwann cells of damaged nerves, and NGF is an autocrine growth factor present in distracted IANs during the early consolidation period after mandibular DO.

Purification and properties of a collagenolytic protease produced by marine bacteriumVibrio vulnificus CYK279H

A collagenolytic enzyme, produced byVibrio vulnificus CYK279H, was purified by ultrafiltration, dialysis, Q-Sepharose ion exchange and Superdex-200 gel chromatography. The enzyme from the supernatant was purified 13.2 fold, with a yield of 11.4%. The molecular weight of the purified enzyme was estimated by SDS-PAGE to be approximately 35.0 kDa. The N-terminal sequence of the enzyme was determined as Gly-Asp-Pro-Cys-Met-Pro-Ile-Ile-Asn. The optimum temperature and pH for the enzyme activity were 35°C and 7.5, respectively. The enzyme activity was stable within the pH and temperature ranges 6.8∼8.0 and 20∼35°C, respectively. The purified enzyme was strongly activated by Zn2+, Li2+, and Ca2+, but inhibited by Cu2+. In addition, the enzyme was strongly inhibited by 1, 10-phenanthroline and EDTA. The purified enzyme was suggested to be a neutral metalloprotease.

Enzyme-assisted extraction of anticoagulant polysaccharide from Liparis tessellatus eggs.

This study aimed to recover a heparin-like anticoagulant polysaccharide from Liparis tessellatus eggs (PLE) by using enzyme-assisted extraction technique. Extraction experiments were carried out using three different enzymes (Alcalase®2.4 L, Flavourzyme®500 MG, and Protamex®) under different conditions of temperature (45, 50, and 55°C), pH (6.5, 7.0, and 7.5), incubation time (24, 36, and 48 h), and enzyme to substrate ratio (E/S=0.5, 1.0, and 1.5%, w/w), which were combined according to a D-optimal design. Statistical analysis of extraction results allowed identifying the variables with greater influence on the extraction yield, and selecting the conditions that maximize the PLE extraction. The best extraction results were achieved when using the Protamex® enzyme in an E/S ratio of 1.34% (w/w), pH 6.60, 47.40°C, during 26.50 h. Under these conditions, a polysaccharide yield of 2.10% (w/w) was obtained. Clotting time measurements, activated partial thromboplastin time, and prothrombin time for evaluation of the anticoagulant properties of PLE were determined and showed increasing activities in correlation with the concentrations used. In the final step, the heparin-like nature of PLE was confirmed by digestion with heparinases I, II, and III, which showed ΔDiHS-0S, ΔDiHS-6S, ΔDiHS-diS1, and ΔDiHS-diS2 at compositions of 0.04, 0.03, 0.35, and 0.24 mol/g, respectively.

The Effects of Mechanically Deboned Chicken Hydrolysates on the Characteristics of Imitation Crab Stick

The effects of adding mechanically deboned chicken (MDC) hydrolysates on the quality characteristics of imitation crab stick (ICS) during storage were investigated. ICS was prepared from Alaska Pollack, chicken breast surimi, and protein hydrolysates enzymatically extracted from MDC. ICS samples were divided into 4 groups: without protein hydrolysate (control), added with 0.5% protein hydrolysate (T1), added with 1.0% protein hydrolysate (T2), and added with 1.5% protein hydrolysate (T3). Results showed that crude protein content did not differ significantly among the ICS samples (p>0.05). ICS sample added with MDC hydrolysates had higher crude fat and ash content but lower moisture content than the control (p<0.05). Lightness was significantly lower in T2 and T3 than in the other groups at 0 and 4 wk of storage. Also, whiteness decreased in the groups contained MDC hydrolysates. Breaking force and jelly strength were higher in samples containing MDC hydrolysates compared to control samples (p<0.05). Additionally, saturated fatty acid contents were lower in the groups containing MDC hydrolysates than in control sample groups (p<0.05). Polyunsaturated fatty acid (PUFA) and essential fatty acids (EFA) were significantly higher in T2 and T3 than the control samples. In particular, all samples containing MDC hydrolysates had reduced thiobarbituric acid-reactive substances (TBARS) values at 4 wk. Free radical scavenging activity also was increased with addition of MDC hydrolysates.

Effects of a Mixed Proportion of Alaska Pollack, Chicken Breast Surimi and Starch on Textural Properties of Sausage

게맛살 및 크래미 생산을 위한 기초 배합비 시험을 위하여 수리미 소시지 제조 시 명태연육만을 이용한 대조구, 명태연육:닭가슴살수리미:전분 비율이 90.91:0:9.09인 T1, 80:0:20인 T2, 62.5:37.5:0인 T3, 58.82:35.3:5.88인 T4, 40:60:0인 T5, 36.36:54.55:9.09인 T6에 대한 조직적 특성을 비교한 결과, 대조구에 비하여 T1의 경우 표면경도, 파괴강도 및 겔 강도가 높게 나타났으며, T2의 경우 파괴강도, 겔 강도 및 접기시험 결과는 높은 반면 T1 및 T2 모두 관능평가 결과는 낮았다. T3의 경우 표면경도, 파괴강도, 변형값, 겔 강도 및 젤리 강도는 높은 반면 응집성과 접기시험 결과는 낮았다. T4의 경우 표면경도, 변형값 및 젤리 강도는 높았다. T5의 경우 파괴강도, 겔 강도 및 젤리 강도 결과는 높은 반면 응집성, 검성 및 씹힘성은 낮았다. T6의 경우 탄력성 및 변형값 결과는 높은 반면 경도, 응집성, 검성, 씹힘성, 파괴강도 및 겔 강도는 낮았다. 특히 T5와 T6 모두 다른 처리구들에 비해 높은 관능적 선호도를 보였으나, 경도, 검성 및 씹힘성 간의 높은 정의 상관관계와 달리 낮은 조직적 특성을 보였다. 따라서 대조구와 비교 시 명태연육:닭가슴살수리미:전분을 62.5:37.5:0으로 혼합한 T3 및 58.82:35.3:5.88로 혼합한 T4가 조직 특성상 양호한 결과를 얻었으며, 관능적 선호도 역시 대조구 차이를 보이지 않아 닭가슴살수리미를 명태연육의 35%까지 대체가 가능한 것으로 판단된다. 【This study was conducted to determine the effect of different proportions of Alaska pollack surimi, chicken breast surimi and starch on textural properties of sausage. Sausage were manufactured such as Alaska pollack surimi(control), T1(90.91:0:9.09), T2(80:0:20), T3(62.5:37.5:0), T4(58.82:35.3:5.88), T5 (40:60:0) and T6(36.36:54.55:9.09) depending on different proportions of Alaska pollack surimi, chicken breast surimi and starch. Brittleness, breaking force and gel strength were significantly higher in T1 than the control(P】

Effects of pH Adjustment on Characteristics of Surimi Using Pork Leg and Chicken Breast.

In this study, we prepared surimi from pork leg and chicken breast by pH adjustments of 3.0 and 11.0. The content of crude protein, yield, water-holding capacity, redness, yellowness, myoglobin(Mb) and metmyoglobin(metMb) were significantly higher in the surimi manufactured from pork leg at adjustment pH 3.0 compared to the other surimi samples; whereas whiteness, myofibrillar protein, breaking force, deformation and gel strength were lower than other samples(P

Antioxidative Properties of Mackerel Scomber japonicus Fed a Diet Fortified with Conjugated Linoleic Acid and Ascidian Halocynthia roretzi Tunic Extract

This study was performed to assess the antioxidative properties of lipid from aquacultured mackerel Scomber japonicus fed with a diet fortified with conjugated linoleic acid (CLA) and ascidian Halocynthia roretzi tunic extracts by radical scavenging assay. The fish were separated into squid oil (Control) and 2.5% CLA (CA25) groups during the 8-week feeding period. The reducing power of each sample showed high levels of activity compared with α-tocopherol and butylated-hydroxyanisol (BHA) at 0.2-1.0 mg/mL of lipid. Inhibition of linoleic acid oxidation in samples from Control and CA25 groups showed similar activity after 2 days of incubation at 40℃. The 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide, and hydroxyl radical scavenging activities of CLA and carotenoid-deposited sample (CA25) were higher than those of the Control group. The results indicated that the lipid extracted from the viscera of mackerel showed slightly higher antioxidant activities than that from the muscle.

Screening and Identification of Alkaline Protease Inhibitor-Producing Marine-derived Actinomyces.

In this study, we screened and identified the bacterial strain showing high alkaline pretense inhibitor activity from marine environment. Nine bacterial strains with alkaline pretense inhibitor activity were isolated from marine sediments. Among them, strain C12 had the highest alkaline pretense inhibitor activity and was selected for further taxonomical study. On the basis of morphological and physiological characteristics, strain C12 was identified as the genus Streptomyces. A phylogenetic analysis of the 165 rDNA showed that the isolated strain was actually a member of the genus Streptomyces, because the determined sequence exhibited a higher homology with Streptomyces thermocarboxydus. Morphological characteristics showed cylindrical spore chain and smooth spore surface by scanning electron microscope. Strain C12 was grown on all media except for ISP 9 agar. This strain could be grown in the medium containing up to 9% NaCl.