• 한국식품위생안전성학회지
• /
• 제8권1호
• /
• pp.55-61
• /
• 1993

토양을 비롯하여 어류, 패류, 조류, 포유류의 소화기관으로부터 Clostridium botulinum 분리를 시도하였다. 총 158개 분리원을 screening한 결과 10개 시료로부터 Clostridium botulinum 분포 가능성을 확인하였으며 6개 시료로부터 Clostridium botulinum을 순수 분리하여 3.8% 분리율을 나타내었다. 분리 균주의 형태적 특징, 배양상의 특성 및 생화학적 특성 등을 표준 균주의 특성과 비교하고 항혈청에 의한 중화시험을 실시하여 분리균주를 동정하였다. Egg york agar에서의 opalescence 생성, 탄수화물 이용성, Egg york GAM 배지상에서의 pearly layer 생성 등으로부터 Clostridium botulinum으로 동정할 수 있었으며 trypsin에 의한 toxicity 활성화, type E 항혈청에 의한 opalescence 생성억제 및 mouse 방어효과가 인정되어 type E 로 동정하였다. 국내에서 시판되고 있는 수 종의 식품을 대상으로 Clostridium botulinum 의 toxin 생성능을 비교하였던 바 식품의 종류, 사용균주에 따라 toxin 생성량에 현저한 차이가 있었다. 분리균주 type E 의 경우 어패류통조림, ham 식품에서 많은 양의 toxin 이 생성되었으며 sausage, 과일통조림 식품에서는 비교적 적었다. 그러나 type A 의 경우에는 어패류, ham , sausage 식품에서 상당량의 toxin 이 생성되었으며 과일통조림에서도 비교적 맣은 양의 toxin이 생성되었다 .

• 한국식품영양학회지
• /
• 제13권2호
• /
• pp.158-163
• /
• 2000

Killer yeast, Hansenular capsulata S-13 were treated with heat, ethylmethane sulfonate and N-methyl-n'-nitro-n-nitrosoguanidine and a mutant(S13-E1), showing 2-fold higher killer toxin activity than that of parent strain to killer sensitive strain, Saccharomyces cerevisiae ATCC 38026 was obtained. Hansenular capsulata S13-E1 showed strong killer toxin activity to Saccharmyces mellis and Saccharomyces sal년 and four strains of gas-producing yeasts from traditional Doenjang and Kochujang. The culture condition for killer toxin production by Hansenular capsulata S13-E1 was optimized to be 1.0% potato extract, each 0.5% of peptone and glucose, and 0.025% MgSO4 with initial pH 4.5 at 3$0^{\circ}C$ and 36 hr of batch cultivation.

• Journal of Microbiology and Biotechnology
• /
• 제6권6호
• /
• pp.451-455
• /
• 1996

Physiological studies on the expression of Bacillus thuringiensis subsp. tenebrionis (Btt) gene coding for insecticidal protein in recombinant Escherichia coli 537 were carried out to identify optimal culture condition. It was necessary to shift culture temperature from 30 to $42^{\circ}C$ to express the gene. Expression of the Btt toxin gene by recombinant E. coli 537 began within one hour after induction. Complex nitrogen sources increased production of the insecticidal protein. The total insecticidal protein was 0.5 g/I when using yeast extract as a complex nitrogen source. Soybean hydrolysate showed apparently the highest induction efficiency. After induction, the cellular content of the insecticidal protein was 5.4 times higher than it had been before induction. The optimal cultivation strategy was found to grow cells for 7hours at $30^{\circ}C$ and then 5-8 hours at $42^{\circ}C$. The optimal cultivation pH for the production of insecticidal protein was 6.5. The Btt toxin produced by the recombinant E. coli 537 was found to have the same level of potency against Colorado potato beetle as the original toxin.

• Journal of Dairy Science and Biotechnology
• /
• 제32권2호
• /
• pp.105-109
• /
• 2014

Food borne pathogens are a growing concern for human health and food safety throughout the world. Milk and dairy products are commonly associated with spoilage or contamination from a wide variety of physical, microbial, and chemical hazards. Milk was inoculated with Staphylococcus aureus and stored at 5, 10, 15, 25, and $35^{\circ}C$ for 7 days, and we monitored the growth change and the variance of toxin production. The growth rate of S. aureus was suppressed in low temperature. We confirmed that growth rate and toxin production were accelerated when the storage temperature was increased. S. aureus began to produce toxins when the number of bacteria was higher than $10^5CFU/mL$. Therefore, managing the storage temperature of milk is important to inhibit the growth and the toxin production of S. aureus.

• Journal of Dairy Science and Biotechnology
• /
• 제32권2호
• /
• pp.101-104
• /
• 2014

Food safety is a global health goal, and food-borne disease are a significant public health threat throughout the world. Dairy products are susceptible to contamination through a wide variety of physical, microbial, and chemical hazards. Risks of microbiological hazards are of immediate and serious concern to human health. Milk was inoculated with Bacillus cereus and stored at 10, 15, 20, and $30^{\circ}C$ for 7 days. We monitored the effect of the temperature on growth rate and variance of toxin production. The growth rate of B. cereus was suppressed in low temperature. We confirmed that the growth rate and the toxin production were accelerated when the storage temperature was increased. B. cereus began to produce toxins when the number of bacteria was higher than $10^7CFU/mL$. Therefore, managing the storage temperature of milk is important to inhibit the growth and the toxin production of B. cereus.

• Journal of Microbiology and Biotechnology
• /
• 제26권1호
• /
• pp.44-55
• /
• 2016

Bacillus cereus is a gram-positive, rod-shaped, spore-forming bacterium that has been isolated from contaminated fermented soybean food products and from the environment. B. cereus produces diarrheal and emetic toxins and has caused many outbreaks of foodborne diseases. In this study, we investigated whether B. amyloliquefaciens RD7-7, isolated from rice doenjang (Korean fermented soybean paste), a traditional Korean fermented soybean food, shows antimicrobial activity against B. cereus and regulates its toxin gene expression. B. amyloliquefaciens RD7-7 exhibited strong antibacterial activity against B. cereus and inhibited the expression of B. cereus toxin-related genes (groEL, nheA, nheC, and entFM). We also found that addition of water extracts of soybean and buckwheat soksungjang (Korean fermented soybean paste made in a short time) fermented with B. amyloliquefaciens RD7-7 significantly reduced the growth and toxin expression of B. cereus. These results indicate that B. amyloliquefaciens RD7-7 could be used to control B. cereus growth and toxin production in the fermented soybean food industry. Our findings also provide a basis for the development of candidate biological control agents against B. cereus to improve the safety of fermented soybean food products.

• KSBB Journal
• /
• 제14권4호
• /
• pp.434-439
• /
• 1999

재래식 메주로부터 생리 기능성의 우수한 효모를 분리하여 이들을 발효산업에 이용하고자 전국 각지의 재래식 메주에서 분리한 47주의 효모중 killer 감수성 균과 장류의 가스 생성 효모에 대하여 killer 활성이 강한 S-13 효모를 선발하여 동정한 후 killer toxin 생산 최적 조건을 검토하였다. S-13의 형태학적, 배양학적 및 생리학적 특성 등을 조사한 결과 Hansenula capsulata로 추정되었고 H. casulata S-13 을 YEPD 배지(pH 4.5)에 접종하여 $25^{\circ}C$에서 36시간 대수기 말기까지 배양하였을때 가장 많은 killer toxin이 생성되었다. 또한, H. capsulata S-13은 재래식 메주에서 분리된 Saccharomyces spp. OE-2 등 7주의 메주 효모와 S. cerevisiae 등 3주의 발효산업 관련 효모에 대하여 Killer 활성을 보였다.

• Journal of Microbiology and Biotechnology
• /
• 제29권10호
• /
• pp.1675-1681
• /
• 2019

Clostridium difficile toxin A is known to cause colonic epithelial cell apoptosis, which is considered the main causative event that triggers inflammatory responses in the colon, reflecting the concept that the essential role of epithelial cells in the colon is to form a physical barrier in the gut. We previously showed that toxin A-induced colonocyte apoptosis and subsequent inflammation were dependent on prostaglandin E2 ($PGE_2$) produced in response to toxin A stimulation. However, the molecular mechanism by which $PGE_2$ mediates cell apoptosis in toxin A-exposed colonocytes has remained unclear. Here, we sought to identify the signaling pathway involved in toxin A-induced, $PGE_2$-mediated colonocyte apoptosis. In non-transformed NCM460 human colonocytes, toxin A exposure strongly upregulated expression of Bak, which is known to form mitochondrial outer membrane pores, resulting in apoptosis. RT-PCR analyses revealed that this increase in Bak expression was attributable to toxin A-induced transcriptional upregulation. We also found that toxin A upregulation of Bak expression was dependent on $PGE_2$ production, and further showed that this effect was recapitulated by an Prostaglandin E2(PGE2) receptor-1 receptor agonist, but not by agonists of other EP receptors. Collectively, these results suggest that toxin A-induced cell apoptosis involves $PGE_2$-upregulation of Bak through the EP1 receptor.

• Journal of Microbiology and Biotechnology
• /
• 제19권1호
• /
• pp.108-112
• /
• 2009

A simplified method for the purification of cholera toxin was developed. The 569B strain of Vibrio cholerae, a recognized hyper-producer of cholera toxin, was propagated in a bioreactor under conditions that promote the production of the toxin. The toxin was separated from the bacterial cells using 0.2-${\mu}m$ crossflow microfiltration, the clarified toxin was passed through the membrane into the permeate, and the bacterial cells were retained in the retentate. The 0.2-${\mu}m$ permeate was then concentrated 3-fold and diafiltered against 10 mM phosphate buffer, pH 7.6, using 30-kDa crossflow ultrafiltration. The concentrated toxin was loaded onto a cation exchange column, the toxin was bound to the column, and most of the impurities were passed unimpeded through the column. The toxin was eluted with a salt gradient of phosphate buffer, pH 7.0, containing 1.0 M NaCl. The peak containing the toxin was assayed for cholera toxin and protein and the purity was determined to be 92%. The toxin peak had a low endotoxin level of $3.1\;EU/{\mu}g$ of toxin. The purified toxin was used to prepare antiserum against whole toxin, which was used in a $G_{M1}$ ganglioside-binding ELISA to determine residual levels of toxin in an oral inactivated whole-cell cholera vaccine. The $G_{M1}$ ganglioside-binding ELISA was shown to be very sensitive and capable of detecting as little as 1 ng/ml of cholera toxin.

• 한국동물학회지
• /
• 제29권3호
• /
• pp.181-189
• /
• 1986

본 연구는 adenylate cyclase의 촉진제인 forskolin과 cholera toxin이 생쥐난자의 핵막붕괴 및 cAMP 합성에 미치는 영향을 조사하고자 수행되었다. 체외난자 배양방법과 adenylate cyclase assay 방법을 이용한 연구의 결과는 아래와 같다. 생쥐난자를 4시간 배양한 결과 대조군의 핵막붕괴율은 93%인데 반해서 forskolin (20-40$\\mu$g/ml)이 함유된 배양액에서 배양한 난자의 핵막붕괴율은 56-36%로써, forskolin의 농도에 비례하여 생쥐난자의 핵막붕괴가 현저하게 억제되었다. Forskolin (80 $\\mu$g/ml)을 3시간 처리한 후, 난자를 forskolin이 제거된 배양액으로 옮겼을 때 난자의 핵막붕괴율이 대조군과 비슷한 정도를 나타내고 있어 forskolin에 의한 핵막붕괴 억제현상은 가역적이었다. 한편, cholera toxin (10-1,000 ng/ml)은 생쥐난자의 핵막붕괴를 억제시키지 못했다. Forskolin (10-80 $\\mu$g/ml)을 생쥐난자 추출물에 첨가할 경우 cAMP합성이 5-18배 증가되었으나, cholera toxin (10-1,000 ng/ml)은 효과가 없었다. 덧붙여, adenylate cyclase의 regulatory unit의 촉진제인 guanidylimido-diphosphate (100$\\mu$M)를 forskolin과 함께 처리하여도 forskolin만 처리한 실험군에 비하여 cAMP합성정도에 변화가 없었다. 또한, cholera toxin과 guanidylimido-diphosphate(100$\\mu$M)를 함께 처리하여도 생쥐난자의 cAMP합성은 증가되지 않았다. 이상의 결과에서 forskolin에 의한 생쥐난자의 핵막붕괴 억제 현상은 난자내의 cAMP농도가 높아짐으로써 야기된 것이라 추측되며, 난자내의 cAMP 농도의 변화가 생쥐난자 성숙에 중요한 역할을 수행할 것이라고 사료된다.