• Journal of Microbiology and Biotechnology
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• v.9 no.5
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• pp.619-623
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• 1999

The C-terminal starch-binding domain of Bacillus cereus $\beta$-amylase expressed in Escherichia coli was purified and crystallized using the vapor diffusion method. The crystals obtained belong to a space group of $P3_2$ 21 with cell dimensions, a=b=60.20${\AA},\; c=64.92{\AA},\; and \; \gamma = 120^{\circ}$ The structure was determined by the molecular replacement method and refined at 1.95 ${\AA}$, with R-factors of 0.181. The final model of the starch-binding domain comprised 99 amino acid residues and 108 water molecules. The starch-binding domain had a secondary structure of two 4-stranded antiparallel p-sheets similar to domain E of cyclodextrin glucanotransferase and the C-terminal starch-binding domain of glucoamylase. A comparison of the structures of these starch-binding domains revealed that the separated starch-binding domain of Bacillus cereus $\beta-Amylase$had only one starch-binding site (site 1) in contrast to two sites (site 1 and site 2) reported in the domains of cyclodextrin glucanotransferase and glucoamylase.

• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.369-372
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• 2007

O-Methyltransferases (OMTs), one of the ubiquitous enzymes in plants, bacteria, and humans, catalyze a methyl-transfer reaction using S-adenosylmethionine and a wide range of phenolics as a methyl donor and acceptor, respectively. Substrates for most bacterial OMTs have largely remained elusive, but recent investigation using BcOMT2, an OMT from Bacillus cereus, suggested that ortho-dihydroxyflavonoids could serve as substrates. To elucidate the functional and structural features of BcOMT2, we expressed, and purified BcOMT2, and crystallized an apoenzyme and its ternary complex in the presence of a flavonoid and S-adenosylhomocysteine. Each crystal diffracted to $1.8{\AA}$ with its space group of C2 and $P2_{1}2_{1}2_{1}$, respectively. Structural analysis of apo-BcOMT2 and its ternary complex will provide the structural basis of methyl transfer onto (iso)flavonoids in a regiospecific manner.

• Journal of Microbiology and Biotechnology
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• v.16 no.4
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• pp.619-622
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• 2006

Biotransformation is a good tool to synthesize regioselective compounds. It could be performed with diverse sources of genes, and microorganisms provide a myriad of gene sources for biotransformation. We were interested in modification of flavonoids, and therefore, we cloned a putative O-methyltransferase from Bacillus cereus, BcOMT-2. It has a 668-bp open reading frame that encodes a 24.6-kDa protein. In order to investigate the modification reaction mediated by BcOMT-2, it was expressed in E. coli as a His-tag fusion protein and purified to homogeneity. Several substrates such as naringenin, luteolin, kaempferol, and quercetin were tested and reaction products were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). BcOMT-2 could transfer a methyl group to substrates that have a 3' functional hydroxyl group, such as luteolin and quercetin. Comparison of the HPLC retention time and UV spectrum of the quercetin reaction product with corresponding authentic 3'-methylated and 4'-methylated compounds showed that the methylation position was at either the 3'-hydroxyl or 4'-hydroxyl group. Thus, BcOMT-2 transfers a methyl group either to the 3'-hydroxyl or 4'-hydroxyl group of flavonoids when both hydroxyl groups are available. Among several flavonoids that contain a 3'- and 4'-hydroxyl group, fisetin was the best substrate for the BcOMT-2.

• Korean Journal of Microbiology
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• v.54 no.4
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• pp.398-409
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• 2018

In the present study, biogenic amine-forming Bacillus spp. and bacteriocin-producing lactic acid bacteria (LAB) isolated from Doenjang were generally identified through 16S rRNA gene sequencing, and the physicochemical and microbiological characteristics of cheonggukjang prepared using the isolated strains were investigated. Biogenic amine-producing bacteria from the samples were identified as Bacillus licheniformis DB102, B. subtilis DB203, B. stearothermophilus DB206, B. pumilus DB209, B. subtilis DB310, B. coagulans DB311, B. cereus DB313, B. amyloliquefaciens DB714, B. amylolique-faciens DB915, B. licheniformis DB917, B. cereus DB1019, B. subtilis DB1020, B. megaterium DB1022. The bacteriocin-producing LAB showed antibacterial effect against biogenic amine-producing Bacillus spp. were identified as Lactobacillus plantarum DLA205, L. brevis DLA501, L. fermentum DLA509, L. acidophilus DLA703, and Enterococcus faecalis DLA804. The bacteriocin produced by the LAB significantly decreased the viable numbers and the amine production ability of the biogenic amine-forming Bacillus spp. in a concentration dependent manner. Therefore, the pH, ammonia nitrogen and biogenic amine content of cheonggukjang prepared by mixed culture of the LAB and Bacillus spp. were significantly decreased compared to the control group.

• Journal of Food Hygiene and Safety
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• v.29 no.1
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• pp.16-20
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• 2014

The prevalence of Bacillus cereus was determined in salad and Kimbab obtained from commercial retailers. Among the 100 salad samples analyzed, 54 samples were negative for B. cereus, whereas the bacterial count was < 10 colony forming units (CFU)/g in 8 samples, < 100 CFU/g in 25 samples, < 1,000 CFU/g in 11 samples, and > 1,000 CFU/g in 2 samples. The mean (standard deviation) was 1.18 log CFU/g (${\pm}0.71$ log CFU/g). In Kimbab, B. cereus was isolated from 20 samples; the mean bacterial count was 1.01 log CFU/g (${\pm}0.71$ log CFU/g). On the basis of the monitoring data, a statistical sampling plan was determined with the NEW sampleplan program (ICMSF), which was used as an analytical tool. To identify the most suitable sampling plan, the microbial limits (m, M) and the maximum allowable number of sample units yielding unsatisfactory test results (c) were varied, but the number of samples units, n = 5, was fixed. Sampling plans showing an acceptable probability (Pa) over 0.95 were considered suitable. Two plans (A and B) were finally suggested. Parameters for plan A are n = 5, c = 0, m = 1,000, and M = 10,000 and for plan B are n = 5, c = 2, m = 100, and M = 1,000. Interestingly, the latter plan was identical to the microbial sampling plan used in New Zealand. Thus, it was concluded that the suggested plan can be used as a sampling plan that is in line with international standards.

• Journal of Microbiology and Biotechnology
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• v.19 no.4
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• pp.387-390
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• 2009

Microbial UDP-glycosyltransferases can convert many small lipophilic compounds into glycons using uridine-diphosphate-activated sugars. The glycosylation of flavonoids affects solubility, stability, and bioavailability. The gene encoding the UDP-glycosyltransferase from Bacillus cereus, BcGT-3, was cloned by PCR and sequenced. BcGT-3 was expressed in Escherichia coli BL21(DE3) with a glutathione S-transferase tag and purified using a glutathione S-transferase affinity column. BcGT-3 was tested for activity on several substrates including genistein, kaempferol, luteolin, naringenin, and quercetin. Flavonols were the best substrates for BcGT-3. The enzyme dominantly glycosylated the 3-hydroxyl group, but the 7-hydroxyl group was glycosylated when the 3-hydroxyl group was not available. The kaempferol reaction products were identified as kaempferol-3-O-glucoside and kaempferol-3,7-O-diglucoside. Kaempferol was the most effective substrate tested. Based on HPLC, LC/MS, and NMR analyses of the reaction products, we conclude that BcGT-3 can be used for the synthesis of kaempferol 3,7-O-diglucose.

• Journal of Food Hygiene and Safety
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• v.39 no.2
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• pp.102-108
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• 2024

This study was performed to establish the epidemiological features of a food poisoning outbreak that occurred in the cafeteria of a company in Chungcheongnam-do Province, Korea, in October 2020, and to recommend measures to prevent similar outbreaks. Twenty-one patients with acute gastroenteritis, three food handlers, seven cooking utensils, and 12 preserved food samples were subjected to viral and bacterial analyses based on procedures described in the "Manual for Detection of Foodborne Pathogens at Outbreaks". Among 135 individuals who had been served the meals, 21 (15.6%) showed symptoms of nausea and vomiting within an hour of consuming the food. Bacillus cereus were isolated from 11 (52.4%) of the 21 patients, one food service employee, one item of cooking ware, and 12 preserved food samples. In addition, we confirmed the toxin genes CER, nheA, and entFM from the isolated B. cereus strains. Pulsed-field gel electrophoresis results indicated that all of the isolated B. cereus strains were closely related, with the exception of strains obtained from one patient and one sample of preserved food. These findings provide evidence to indicate that the isolated B. cereus originated from preserved foods and an unhygienic eating environment. This outbreak highlights that the provision of food in non-commercial food systems must be thoroughly managed. In addition, it emphasizes the necessity for the correct and timely identification of causal pathogens for tracing the cause of food poisoning outbreaks, and the need to preserve food under appropriate conditions. To prevent similar cases of food poisoning, it is necessary to investigate cases based on an epidemiological approach and share the findings.

• Microbiology and Biotechnology Letters
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• v.48 no.1
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• pp.64-71
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• 2020

A total of 262 bacterial strains were isolated from clay minerals, bentonite and zeolite, in Gyeongsangbukdo, Republic of Korea, and their hydrolytic enzyme activities were analyzed. Most of the isolated strains belonged to Micrococcales and Bacillales order. Of strains, 96 strains produced α-amylase activity, 42 strains showed cellulase activity, 111 strains had pectinase activity, and 70 strains showed protease activity. Among them, 177 isolates exhibited one or more of the hydrolytic enzyme activities and in particular Bacillus cereus MBLB1321, B. albus MBLB1326 and KIGAM017, B. mobilis MBLB1328, MBLB1329 and MBLB1330 showed all of the enzyme activities. These results demonstrate the diversity of functional Bacillus species in clay minerals as vital sources for the discovery of industrially valuable hydrolytic enzymes, which have a great commercial prospect in various bio-industrial applications.

• Applied Biological Chemistry
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• v.46 no.3
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• pp.235-239
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• 2003

Thirteen sesquiterpene lactones isolated from the flower of Chrysanthemum coronarium L., which has been widely cultivated in Korea as a vegetable for a long time, were investigated their antimicrobial activities against eight bacteria and five phytopathogenic fungi. The antimicrobial activities of dihydrochrysanolide (6) and 1-epi-dihydrochrysanolide (7) showed strong activities against all the bacteria such as Bacillus subtilis, Bacillus cereus, Staphylococcus aureus and Vibrio parahaemolyticus. Especially, Staphylococcus aureus was investigated that have very strong antibacterial activity to $1.56\;{\mu}g{\cdot}disc^{-1}$, respectively. Also, most of sesquiterpene lactones, which have ${\alpha}-methylene-{\gamma}-butyrolactone$ group, were exhibited strong activity to Gram(+) bacteria than Gram(-) bacteria. In the antifungal test, Rhizoctonia solani and Phytophthora capsici known as phytopathogenic fungi have exhibited all extensive activity about compounds that have ${\alpha}-methylene-{\gamma}-butyrolactone$ group.

• Journal of Applied Biological Chemistry
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• v.49 no.3
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• pp.90-94
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• 2006

Bactericidal activity of grapefruit seed extract (GSE)-based disinfectant, as a safe disinfectant, was measured against five bacteria by Korean Food & Drug Administration (KFDA) dilution-neutralization method. GSE-based disinfectant showed a 99.9999% bactericidal activity against Escherichia coli ATCC 10536, Salmonella typhi ATCC 29629, Staphylococcus aureus ATCC 6538, Bacillus cereus ATCC 11778, and Listeria monocytogenes ATCC 1911 at the concentration of 2.15% GSE. It showed better bactericidal activity against Gram-negative bacteria of E. coli ATCC 10536 and S. typhi ATCC 29629 at lower concentration of GSE (0.43%). Based on the results, it was suggested that a possible bactericidal mechanism of GSE active ingredients was due to the abrupt osmotic shift during the bactericidal activity test by KFDA method.