• Journal of Microbiology and Biotechnology
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• 제6권5호
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• pp.340-346
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• 1996

In order to find out if staphylococci occur in significant numbers in Korean fermented fish products, a total of 40 different fermented fish products were collected from different markets in Korea and analyzed for their physico-chemical and microbiological states. The pH, salt concentration and water activity of the products were measured and the total viable cell count and the number of Staphylococcus grown on mannitol salt agar were determined. The identification of the strains of Staphylococcus were made by API Staph Strip and MIS identification kits, and the physiological properties of the identified strains were further characterized by different conventional methods. The pH, salt content and water activity of fermented fish samples varied widely from 4.8 to 7.1, 7.4-28.7$%$ and 0.77-0.84, repectively, depending on the type of product. The total viable cell count varied from $10^4-10^9$ cfu/ml, and most of the samples had $10^5-10^6$ cfu/ml No correlation was found between the viable cell count and the pH, NaCl concentration and water activity of the samples. Among the 35 colonies identified as Staphylococcus strains by the identification kits, S. xylosus was the most frequently occurring strain marking 17, and S. warneri was 8, S. epidermidis 4 and S. cohnii 2. S. hominis, S. saprophyticus, S. haemolyticus and S. aureus were also identified once each. In some samples (K-3, P-6, K-8, G-5 and G-10), 2-3 different species of Staphylococcus were found. Considering the region of sampling, among the 10 samples from Kunsan 5 were identified as S. warneri, while in the other regions S. xylosus was predominant. Although the physiological characteristics of the identified strains were generally consistent with those in Bergey's Manual, some discrepances were also observed. All the strains were highly salt tolerant, growing in the media containing over 18$%$ NaCl. All the strains except S. aureus (G-11) showed negative in hemolysis activity, plasma coagulation and DNase tests. All the strains including S. aureus (G-11) showed negative in enterotoxin test.

• Food Science and Biotechnology
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• 제14권4호
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• pp.461-465
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• 2005

To determine the cause of wet noodle spoilage, microorganisms isolated from wet noodles were identified and characterized. In addition, the growth inhibitory effects of organic acid mixture (OA: lactic acid 27.8%, acetic acid 12.0%, succinic acid 1.0%) and sodium dehydroacetate (SD) on the isolated strain were estimated in nutrient broth medium. The isolated strain was Gram-positive, rod shaped, motile, and spore forming. Based on physiological characteristics and the API 50 CHB-kit test results for the assimilation of 49 carbohydrates, the isolated strain was identified as Bacillus amyloliquefaciens (92.6%), which is able to degrade starch. Decimal reduction times (D-values) at 100, 105, and $110^{\circ}C$ for spores of B. amyloliquefaciens were 8.5, 5.1, and 2.5 min, respectively, and the z-value was $12.8^{\circ}C$. We estimated that B. amylo-liquefaciens isolated from spoiled wet noodles was a thermophilic species having high heat-resistance. Viable cell numbers in wet noodles and broth medium inoculated with B. amyloliquefaciens were decreased by 2-4 log cycles by combined treatment with 0.03 or 0.05% OA and 0.3% SD. These results revealed that OA combined with SD could be used as a potential agent to inhibit B. amyloliquefaciens in wet noodles.

• Food Science and Biotechnology
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• 제15권5호
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• pp.677-682
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• 2006

Strain HY701 was isolated from human feces for probiotic use by selecting highly resistant isolates to artificial gastric acid and bile acid. Strain HY701 was identified as Lactobacillus reuteri using 16S rDNA sequencing, and tentatively named L. reuteri HY701. The resistance of L. reuteri HY701 to artificial gastric acid (PH 2.5) was high with a survival rate of over 90%. L. reuteri HY701 also showed high tolerance to artificial bile acid after incubation in artificial gastric acid. Using the API ZYM test kit, the carcinogenic enzymes (${\beta}$-glucuronidase and (${\beta}$-glucosidase were not detected with L. reuteri HY70l, while the beneficial enzyme (${\beta}$-galactosidase was weakly detected. L. reuteri HY701 was sensitive to $100\;{\mu}g/mL$ nisin, $20\;{\mu}g/mL$ roxithromycin, $15\;{\mu}g/mL$ erythromycin, but resistant to $20\;{\mu}g/mL$ streptomycin, $10\;{\mu}g/mL$ tetracycline, $20\;{\mu}g/mL$ ciprofloxacin, $20\;{\mu}g/mL$ nystatin, $20\;{\mu}g/mL$ gentamycin, $10\;{\mu}g/mL$ doxycycline, $10\;{\mu}g/mL$ chloramphenicol, and $20\;{\mu}g/mL$ ampicillin. L. reuteri HY701 was shown to possess bactericidal activity as it inhibited the growth of Listeria monocytogenes ATCC 19111 and Escherichia coli JM109 completely within 24 hr of incubation. These results indicate that L. reuteri HY701 could be used as a probiotic strain.

• Food Science and Biotechnology
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• 제17권3호
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• pp.519-526
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• 2008

To improve the quality of traditional kochujang, strains with high protease and amylase activity were isolated and identified from Sunchang traditional kochujang. Twenty-three strains strongly producing protease and 16 strains strongly producing $\alpha$- and $\beta$-amylase were isolated by using 1% isolated soy protein agar medium and 2% starch agar medium, respectively. Protease activities of the IA7, I5, and IA2 strain were 22.5, 21.2, and 20.6 unit/mL, respectively, and were higher than those of the other strains. Stains with high $\alpha$-amylase activity included K9 (967.8 unit/mL), K14 (828.3 unit/mL), K13 (662.5 unit/mL), K8 (601.5 unit/mL), and K11 (405.9 unit/mL). The $\beta$-amylase activity of the K11 strain was the highest, 34.3 unit/mL, among the isolated strains. Based on morphological, physiological properties, and API 50CHB-kit test for assimilation of 49 carbohydrates, 8 strains selected according to protease, $\alpha$-amylase, and $\beta$-amylase activities were tentatively identified as Bacillus megaterium (IA2), Bacillus subtilis (IA7, 15), Bacillus amyloliquefaciens (K8, K9, K11, and K13), and Bacillus stearothermophillus (K14). The IA7, 15, and K11 strains were finally identified as B. subtilis (99% ID) based on 16S rDNA sequencing.

• KSBB Journal
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• 제19권4호
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• pp.315-320
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• 2004

본 연구에서는 환경호르몬 물질의 하나인 스티렌 다이머를 분해하는 미생물을 자연계로부터 분리하고자 하였다. 분리결과 스티렌 다이머 분해 능력이 있는 strain YH3를 분리하였다. Strain YH3은 단일균주가 아닌 3종류의 서로 다른 미생물상을 이루고 있었다. 동정을 한 결과 strain YH32는 Pseudomonas sp.로, strain YH33은 Klebsiella pneumoniae로 동정되었으나, strain YH31은 동정이 되지 않았다. 이들 세균주는 단일균 혹은 두 종류씩 짝을 지어 배양 하여도 스티렌 다이머를 분해하지 못하였으나 세 균주가 혼합되었을 때는 O. $D_{660nm}$ 값과 색도의 변화를 통해 생장을 확인 할 수 있었다. 세 균이 혼합된 복합균주 YH3을 대상으로 균주의 최적 생장 조건을 검토한 결과, 35$^{\circ}C$, pH 7.0, 기질 농도 1,000ppm (v/v)으로 각각 조사되었다. 또한, 유기용매에 대한 내성은 복합균주 YH3는 logP 값이 3.1 이상에서 생장하였고, 방향족화합물인 ethyl benzene과 제초제의 일종인 2,4-D를 분해하였다. 그러나 benzene, toluene, xylene 및 styrene trimer는 분해가 어려운 것으로 확인되었다. 그리고 TLC 분석 결과, 배양 5일째부터 스티렌 다이머의 중간대사산물이 관찰되었다.

• 한국축산식품학회지
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• 제34권1호
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• pp.106-114
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• 2014

Folic acid, one of the B group of vitamins, is an essential substance for maintaining the functions of the nervous system, and is also known to decrease the level of homocysteine in plasma. Homocysteine influences the lowering of the cognitive function in humans, and especially in elderly people. In order to determine the strains with a strong capacity to produce folic acid, 190 bacteria were isolated from various kinds of jeotgal and chungkuk-jang. In our test experiment, JA71 was found to contain $9.03{\mu}g/mL$ of folic acid after 24 h of incubation in an MRS broth. This showed that JA71 has the highest folic acid production ability compared to the other lactic acid bacteria that were isolated. JA71 was identified as Lactobacillus plantarum by the result of API carbohydrate fermentation pattern and 16s rDNA sequence. JA71 was investigated for its physiological characteristics. The optimum growth temperature of JA71 was $37^{\circ}C$, and the cultures took 12 h to reach pH 4.4. JA71 proved more sensitive to bacitracin when compared with fifteen different antibiotics, and showed most resistance to neomycin and vancomycin. Moreover, it was comparatively tolerant of bile juice and acid, and displayed resistance to Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus with restraint rates of 60.4%, 96.7%, and 76.2%, respectively. These results demonstrate that JA71 could be an excellent strain for application to functional products.

• 한국해양공학회지
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• 제25권3호
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• pp.73-84
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• 2011

This is the fifth in a series of companion papers dealing with the dynamic hardening properties of various marine structural steels at intermediate strain rates. Five steps of strain rate levels (0.001, 1, 10, 100, 200/s) and three steps of temperature levels (LT ($-40^{\circ}C$), RT, and HT ($200^{\circ}C$)) were taken into account for the dynamic tensile tests of three types of marine structural steels: API 2W50 and Classifications EH36 and DH36. The total number of specimens was 180 pieces. It was seen that the effects of dynamic hardening became clearer at LT than at RT. Dynamic strain aging accompanying serrated flow stress curves was also observed from high temperature tests for all kinds of steels. The dynamic hardening factors (DHFs) at the two temperature levels of LT and RT were derived at the three plastic strain levels of 0.05, 0.10, 0.15 from dynamic tensile tests. Meanwhile, no DHFs were found for the high temperature tests because a slight negative strain rate dependency due to dynamic strain aging had occurred. A new formulation to determine material constant D in a Cowper-Symonds constitutive equation is provided as a function of the plastic strain rate, as well as the plastic strain level. The proposed formula is verified by comparing with test flow stress curves, not only at intermediate strain rate ranges but also at high strain rate ranges.

• International Journal of Industrial Entomology and Biomaterials
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• 제25권2호
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• pp.195-203
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• 2012

In reared populations of Allomyrina dichotoma, commercial insects, the skin of last instar larvae was changed softer with opaque white, and infested grubs eventually died. To clarify the cause of the symptom, we collected the larvae of A. dichotoma from five farms and examined their intestinal bacterial florae using pyrosequencing technique. From those results, a member of Paenibacillus was found only in the larvae showing the symptom of disease. Through PCR analysis using a Paenibacillus specific primer set, we obtained the partial 16S rRNA gene sequence and confirmed the microbe as Paenibacillus sp. For clear identification, a whole guts was extracted from each larva showing the sign of the disease and incubated at $70^{\circ}C$ for 15 min to isolate spore forming bacteria. After then, each content of guts was cultured on $MYPGP_{NAL}$ agar medium($12.5{\mu}g/ml$ of nalidixic acid) at $30^{\circ}C$. The 16S rRNA gene sequence analysis for the isolated bacteria showed that they were closely related to P. rigui(97.9% similarity), to P. chinjuensis(96.1% similarity), and to P. soli(95.3% similarity). Additional tests including API test and cellular fatty acid composition analysis were performed, but the strain couldn't be identified at species level, suggesting it may represent novel species of the genus Paenibacillus.

• 한국식품과학회지
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• 제31권5호
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• pp.1324-1329
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• 1999

국내 유통중인 냉동만두와 피자 중 L. monocytogenes의 분포와 분리균의 특성을 조사하기 위하여 1998년 8월부터 11월에 걸쳐 시료 72개를 구입하여 실험하였다. 전체 냉동식품 중 9.7%(7개)에서 L. monocytogenes가 분리되었으며 냉동만두 중 11.1%,피자 중 5.6%가 오염되어 있었다. USDA와 FDA방법. 그리고 modified cold enrichment 방법 중 USDA방법이 가장 L. monocytogenes의 분리율이 높았으며 분리된 L. monocytogenes 혈청형은 4였다. PCR실험결과 CAMP test와 API Listeria kit를 사용하여 분리된 균주가 L. monocytogenes임이 확인되었다. USDA방법과 PCR을 이용하여 L. monocytogenes를 분리하고 확인하는데 3-4일 정도의 시간이 소요되어 시간을 단축시킬 수 있는 분리 및 확인방법의 개발이 필요하리라 사료된다. 분리된 L. monocytogenes의 내열성을 조사한 결과 tryptic soy broth에서 D값이 $60^{\circ}C$에서 49.2초, $65^{\circ}C$에서 8.8초였으며 냉동식품의 안전한 사용을 위하여 L. monocytogenes의 분리율이 높은 식품에서 D값의 측정이 필요하다고 사료된다.

• 한국식품과학회지
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• 제22권2호
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• pp.129-133
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• 1990

누룩으로부터 유당 분해능과 $CO_2$ 생성능이 있는 균주를 분리하였다. 분리한 균주의 세포파쇄액을 ${\beta}-galactosidase$ 조효소액으로 하여 효소생산을 위한 최적 배양조건에 대해 조사한 결과 $28^{\circ}C$에서 배양하는 경우 균체량과 효소생산량은 pH4.5-5.0, 28시간에서 최대치를 나타내었다. 탄소원으로서는 galactose와 Sucrose를, 질소원으로서는 urea를 사용했을 때 효소 생산량이 증가하였다. 분리한 균주의 유당 발효능을 조사하기 위해서 유청에 접종하여 알코올 생산량을 검토한 결과 유청에 있는 유당만을 이용한 경우에 최대 알코올 생산함량이 2% 정도인데, 유청에 20%(w/v)의 당 첨가에 의해서 알코올 생산함량이 12%로 증가하였다. 누룩으로부터 분리한 균주와 본 실험에서 비교군으로 사용한 S. fragilis ATCC 8583의 유당 분해능과 알코올 생성능은 매우 유사하나 유당발효에의 최적 pH가 누룩 yeast는 4.5인데 비해서 S. fragilis는 3.5이었다.