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Yoon, Yohan;Sofos, John N. Sookmyung Women's University Research Institute of 2011 여성과 건강 Vol.6 No.2
This study used various approaches to investigate the potential association of autoinducer-2 (AI-2) presence with thermal and acid resistance of Salmonella cultures. Salmonella Thompson strains RM1987N (luxS-positive; AI-2 positive) and RM1987NLUX (luxS-negative; AI-2 negative) were exposed to 55 °C (6 h) in Luria-Bertani (LB) broth, while the /w.Y5-negative 5. Thompson strain and a Salmonella Typhimurium / luxS-positive strain were exposed to 55 °C in AI-2-positive or -negative preconditioned (PC) media derived from S. Thompson and Escherichia coli 0157:H7 luxS-positive and -negative strains. In addition, the /HA\S'-negative S. Thompson strain was subjected to pH 3.5 PC media (35 °C, 6 h) with or without AI-2 activity, and acid-adapted or nonadapted S. Thompson strains were exposed to pH 3.0 LB broth (35 °C, 6 h). Surviving bacterial populations during exposure to 55 °C LB were not different between luxS -negative and -positive S. Thompson strains. In addition, heating at 55 °C of the luxS-negative S. Thompson strain in AI-2-positive and -negative PC media resulted in similar (P≥0.05) survivor counts. Furthermore, surviving cell counts of S. Typhimurium (luxS-positive) in 55 °C AI-2-positive PC media were not different (P > 0.05) than those in AI-2 negative PC media. No differences in surviving cell counts of the luxS-negative S. Thompson strain was found when exposed to pH 3.5 Al-2-positive and -negative PC media. Also, survivors of acid-adapted or nonadapted cells of luxS-negative and -positive S. Thompson strains were not different following exposure to pH 3.0 LB. The results indicated that, under the conditions of this study, AI-2-bascd quorum sensing did not appear to be associated with heat and acid resistance of Salmonella.
Identification of Inhibitory Effect on Streptococcus mutans by Oleanolic Acid
Yohan Yoon(윤요한),Kyoung-Hee Choi(최경희) 한국생명과학회 2010 생명과학회지 Vol.20 No.3
구강에 상주하는 미생물 중, Streptococcus mutans는 충치 및 치주염의 원인인 치아플라그를 형성하는데 중요한 역할을 한다. Phytochemical은 식물에서 추출된 화학성분으로서, 사람의 건강에 유익한 영양물질로서 많은 연구들이 진행되어왔다. 본 연구는 이 phytochemical이 중요 구강미생물인 S. mutans에 대한 효과를 살펴보았다. 최근에 Thomson seedless raisin에서 여러 phytochemicals가 추출되었는데, 그 중 oleanolic acid (OA)와 5-(hydroxymethyl)-2-furfural (HF)의 임상적으로 중요한 여러 미생물에 대한 항균활성효과를 확인한 결과, OA가 그람음성균들에게는 항균활성효과가 나타나지 않았고, 그람양성균들에만 항균활성효과를 보였다. 그러나, HF의 경우에는 모든 균주에 대해 항균활성을 나타내지 않았다. 또한, OA는 S. mutans 균주의 표면부착과 생균막의 형성을 저해하기도 하였다. 따라서, 이 연구결과들은 OA가 치아에 존재하는 S. mutans의 생육 및 여러 생리적 특성들을 저해하므로 항플라그제나 항충치약으로서의 활용가능성을 확인할 수 있었다. Among endogenous oral microflora, Streptococcus mutans plays a critical role in dental plaque formation, which mainly contributes to the development of caries and periodontal disease. Phytochemicals are plant-derived chemical compounds that have been studied as beneficial nutrients to human health. The purpose of this study was to determine the effects of phytochemicals against S. mutans. Among them, oleanolic acid (OA) and 5-(hydroxymethyl)-2-furfural (HF) from Thomson seedless raisins were tested for anti-microbial effects against various clinically important bacteria. OA inhibited the growth of Gram-positive bacteria, but not Gram-negative bacteria. However, HF did not display any antibacterial effect against any of the strains tested. OA also exhibited inhibitory effects in surface adherence and biofilm formation of S. mutans. The results suggest that OA can be utilized as a potential anti-plaque and anti-caries agent by controlling the physiological characteristics of S. mutans on teeth.
Yohan Yoon,Gyeongyeol Kim,Minji Nam,Won-Bo Shim,Eunkyoung Seo,Jae-Hun Kim,Ju-Woon Lee,Myung-Woo Byun,Duck-Hwa Chung 한국식품과학회 2009 Food Science and Biotechnology Vol.18 No.1
This study evaluated glucose effect on Listeria monocytogenes survival under gamma irradiation and NaCl stress. L. monocytogenes in phosphate buffered saline (PBS) plus glucose (0-4%) was treated with gamma irradiation (0-0.5 kGy), and the samples were then exposed to NaCl (0-9%) in tryptic soy agar plus 0.6% yeast extract. D₁? and t₃D values were determined, and a model for prediction of D₁? values was developed. Cell counts of L. monocytogenes reduced as irradiation dose increased, and L. monocytogenes in PBS (no glucose) was more sensitive to irradiation and NaCl compared to those in PBS (2 or 4% glucose). D₁? values were 0.07-0.1, 0.12-0.16, and 0.13-0.15 kGy for 0, 2, and 4% glucose, respectively. The t₃D values were 0.22-0.3 (0% glucose), 0.35-0.48 (2% glucose), and 0.40-0.44 (4% glucose). A model performance was acceptable. These results indicate that glucose in foods would increase the resistance of L. monocytogenes to gamma irradiation and NaCl stress.
Yoon, Young Min,Park, Jong-Heum,Lee, Ji-Hye,Park, Jae-Nam,Park, Jin-Kyu,Sung, Nak-Yun,Song, Beom-Seok,Kim, Jae-Hun,Yoon, Yohan,Gao, Meixu,Yook, Hong-Sun,Lee, Ju-Woon Elsevier 2012 Radiation physics and chemistry Vol.81 No.8
<P><B>Abstract</B></P><P>The purpose of this study was to compare the effect of gamma irradiation on the total bacterial population and the sensory quality of <I>Dakgalbi</I> irradiated before and after cooking. Fresh chicken meat was cut into small pieces and used to prepare <I>Dakgalbi</I>. For the preparation of <I>Dakgalbi</I> cooked with gamma-irradiated chicken meat and sauce (IBC), raw chicken meat and <I>Dakgalbi</I> sauce were irradiated and then stir-fried. For the preparation of <I>Dakgalbi</I> irradiated after cooking with raw chicken meat and sauce (IAC), raw chicken meat and <I>Dakgalbi</I> sauce were first cooked and subsequently irradiated. Under the accelerated storage condition of 35°C for 7 days, bacteria in IBC were below the detection limit (1log CFU/g) on day 1 but were detected on day 2 and gradually increased hereafter. In IAC, on the other hand, bacteria were not detected at all. Evaluation of sensory quality also decreased on both samples. However, IAC showed a better trend. Our results indicate that IAC protocol was a more effective method for reducing bacterial growth in <I>Dakgalbi</I>.</P> <P><B>Highlights</B></P><P>► We compared the microbial safety and sensory property of <I>Dakgalbi</I> irradiated before and after cooking. ► <I>Dakgalbi</I> irradiated after cooking can be more effective processing method on microbial safety. ► Sensory property decreased on both <I>Dakgalbis</I> by irradiation-induced off-flavor. ► <I>Dakgalbi</I> irradiated after cooking showed a better tendency on the sensory evaluation.</P>
Yoon, Yohan,Choi, Kyoung-Hee Korean Society for Food Science of Animal Resource 2010 한국축산식품학회지 Vol.30 No.5
The objective of this study was to evaluate the inhibition of Listeria monocytogenes growth by oleanolic acid under sublethal stresses of NaCl and pH. L. monocytogenes ATCC15313 (6 log CFU/mL) was inoculated in microplate wells containing brain heart infusion (BHI) broth supplemented with oleanolic acid in various amounts (0, 0.25, 0.5, 1.0, 1.5, 2.0, and $4.0\;{\mu}g/mL$), and different pHs (5 and 7) and NaCl concentrations (0, 3, and 6%), followed by incubation under accelerated storage condition ($37^{\circ}C$, 48 h). The optical density (OD) of the samples was measured at 0, 6, 12, 24, and 48 h at 600 nm. After the lag phase duration was observed at the early stage of incubation, the OD values of L. monocytogenes significantly increased (p<0.05) in BHI broth formulated with 0 and 3% of NaCl during accelerated storage at pH 5 and 7. However, the growth of L. monocytogenes in 6% NaCl and at less than $0.5\;{\mu}g/mL$ of oleanolic acid had no growth at pH 5 and only gradual growth at pH 7. Moreover, L. monocytogenes generally had lower OD values as the concentrations of oleanolic acid increased. As expected, the OD values of L. monocytogenes were generally higher (p<0.05) at pH 7 than at pH 5. These results indicate that oleanolic acid should be useful in inhibiting the growth of L. monocytogenes.
YOON, HYUNJOO,LEE, JOO-YEON,SUK, HEE-JIN,LEE, SUNAH,LEE, HEEYOUNG,LEE, SOOMIN,YOON, YOHAN International Association for Food Protection 2012 Journal of food protection Vol.75 No.12
<P>This study developed models to predict the growth probabilities and kinetic behavior of Salmonella enterica strains on cutting boards. Polyethylene coupons (3 by 5 cm) were rubbed with pork belly, and pork purge was then sprayed on the coupon surface, followed by inoculation of a five-strain Salmonella mixture onto the surface of the coupons. These coupons were stored at 13 to 35°C for 12 h, and total bacterial and Salmonella cell counts were enumerated on tryptic soy agar and xylose lysine deoxycholate (XLD) agar, respectively, every 2 h, which produced 56 combinations. The combinations that had growth of ≥0.5 log CFU/cm2 of Salmonella bacteria recovered on XLD agar were given the value 1 (growth), and the combinations that had growth of <0.5 log CFU/cm2 were assigned the value 0 (no growth). These growth response data from XLD agar were analyzed by logistic regression for producing growth/no growth interfaces of Salmonella bacteria. In addition, a linear model was fitted to the Salmonella cell counts to calculate the growth rate (log CFU per square centimeter per hour) and initial cell count (log CFU per square centimeter), following secondary modeling with the square root model. All of the models developed were validated with observed data, which were not used for model development. Growth of total bacteria and Salmonella cells was observed at 28, 30, 33, and 35°C, but there was no growth detected below 20°C within the time frame investigated. Moreover, various indices indicated that the performance of the developed models was acceptable. The results suggest that the models developed in this study may be useful in predicting the growth/no growth interface and kinetic behavior of Salmonella bacteria on polyethylene cutting boards.</P>