• Korean Journal of Microbiology
• /
• v.51 no.2
• /
• pp.141-147
• /
• 2015

Four halophilic bacteria were isolated from a salt water tank of more than 25% above salinity used for production of salt. HJS1 and HJS6 strains were identified as having ${\beta}$-glucosidase producing capabilities at high salinity. ${\beta}$-Glucosidase produced from these bacterial strains showed the best activity at 56-79 U/ml in NaCl (0-5%), showing the highest ${\beta}$-glucosidase activity at NaCl 3%. A salt tolerant ${\beta}$-glucosidase can maintain at least 75% activity of the enzyme in 0-20% NaCl concentration. The 16S rRNA gene sequences of strains HJS1 and HJS6 shows 99.8% similarity with Roseivivax roseus $BH87090^T$. Those sequences were registered as AB971835 and AB971836 in the NCBI GenBank. DNA-DNA hybridization test revealed that both strains showed 90.1 to 90.3% hybridization values with R. roseus $BH87090^T$, which was the closest phylogenetic neighbor. Major Cellular fatty acids of strains HJS1 and HJS6 were $C_{16:0}$, $C_{18:1}$ ${\omega}7c$, $C_{19:0}$ cyclo ${\omega}8c$ and 11-methyl $C_{18:1}$ and the major quinone was Q-10. Their fatty acid composition and quinone were very similar to Roseivivax roseus $BH87090^T$. Meanwhile, Roseivivax roseus $BH87090^T$ did not produce any ${\beta}$-glucosidase. Based on the molecular and chemotaxonomic properties, strains HJS1 and HJS6 were identified as members of Roseivivax roseus.

• Applied Biological Chemistry
• /
• v.40 no.6
• /
• pp.484-489
• /
• 1997

The characteristics of growth and esterase activity of bacterial strains isolated from acid hydrolysed soybean protein were examined. All the isolated strains having decomposition activity of p-hydroxybenzoic acid butyl ester and esterase producing activity were identified as Bacillus sp. by morphological and biochemical methods. The specific growth rates, esterase activities and p-hydroxybenzoic acid butyl ester decomposition activities of isolated strains were $0.844{\sim}1.213\;h^{-1}$, $21{\sim}222\;mU/ml$ and $5.4{\sim}8.1\;mU/ml$, respectively. In the fermentation of Bacillus sp. KB8 strain which had the highest esterase producing activity, growth, extracellular excretion and intracellular synthesis of esterase were inhibited by adding NaCl in the culture broth. Esterase producing activity gradually increased after late exponential growth phase, until maximum value of 420 mU/ml reached after 64 hours culture period. Esterase of Bacillus sp. KB8 strain was stable up to $50^{\circ}C$ for 30 minutes, but was inactivated by heating for 30 minutes at $70^{\circ}C$. The enzyme activity exponentially decreased during the incubation time at the temperatures of $60^{\circ}C$ and $65^{\circ}C$.

• Korean Journal of Food Science and Technology
• /
• v.47 no.4
• /
• pp.446-451
• /
• 2015

The market for green vegetable juice (GVJ) is growing owing to the increasing demand for healthy food; however data on the safety and quality of GVJ are poorly reported. The objective of this study was to investigate the change in microbial community in GVJ during storage and its contamination by E. coli O157:H7. The microbial community was analyzed via culturable and non-culturable methods at 5, 10, and $25^{\circ}C$ for different storage times. In the non-culturable method, denaturing gradient gel electrophoresis (DGGE) was used. The initial bacterial concentration was $2.92{\times}10^5CFU/mL$, which exceeded the limit prescribed by the Korean Food Hygiene law. The results of the DGGE analysis indicated that the microbial community during storage was diverse and the spoilage lactic acid bacteria were prevalent at a later stage. Other bacteria such as Rahnella, Citrobacter, Pseudomonas, and Cyanobacteria were identified. Thus, the results strongly emphasize the need to pay attention to GVJ production safety, especially with respect to temperature control, in order to prevent the growth of foodborne pathogens such as E. coli O157:H7 and other spoilage bacteria.

• Korean Journal of Food Science and Technology
• /
• v.43 no.4
• /
• pp.490-494
• /
• 2011

Although bacterial outbreaks from ready-to-eat foods have increased, little information is available on microbial quality of sprouts in markets. Fifty sprouts and 30 salads were collected from wholesale markets. Total aerobic count (TAC), coliform, Escherichia coli, and some pathogens were detected. TAC for sprouts was 7.95 log CFU/g and 6.70 for salads, indicating that sprouts were more contaminated by 1 log CFU/g than that of salads. The numbers of coliform were 6.69 log CFU/g for sprouts and 5.42 for salads. E. coli was detected in 16 of 50 sprout samples at 2.38 log CFU/g and eight of 30 salads at 2.21 log CFU/g. Bacillus cereus was detected in 29 of 50 sprout samples and 16 of 30 salads, and the counts were mostly <3 log CFU/g. Salmonella, Staphylococcus aureus, Listeria monocytogenes, Campylobacter jejuni, and Clostridium perfringens were not detected. Therefore, although pathogens may not be a high risk for these foods, the high TAC and E. coli contamination require improved production and distribution methods, particularly for sprouts.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.32 no.2
• /
• pp.357-369
• /
• 2005

Streptococci are Gram-positive, facultative anaerobes and have no catalase activities. Among mutans streptococci containing ${\alpha}-type$ hemolytic activity, S. mutans is a causative agent for dental caries. As well as acid production yielding the demineralization of tooth enamel, adherence and colonization of S. mutans to the teeth are also important for its virulence. These early colonization are accomplished by the bacterial fibrillar protein, Antigen I/II (Ag I/II) and glucosyltransferase (GTF). Therefore, Ag I/II and GTF are reasonable targets for the development of vaccine against S. mutans GS-5. The ag I/II and gtfD genes from S. mutans GS-5 were cloned and sequenced. Sequence analyses showed the nucleotides sequence of cloned genes had high homology to the sequences previously reported. The sequence alignment of 280 nucleotides between the cloned Ag I/II and the available sequence of the corresponding S. mutans GS-5 showed the perfect match. Comparing with the sequence of gtfD from S. mutans UA159, the corresponding nucleotide sequence of S. mutans GS-5 showed some mismatches and the mismatches introduced changes in four residues out of 105 amino acids, yielding four missense mutations.

• Asian-Australasian Journal of Animal Sciences
• /
• v.31 no.8
• /
• pp.1336-1344
• /
• 2018

Objective: This study aimed to observe whether high-pressure processing (HPP) affected aroma development and the degradation rate of umami taste-related ATP breakdown products, specifically inosinic acid in grass-fed beef during vacuum aging. Methods: Strip loin (longissimus lumborum) cuts obtained from six grass-fed Friesian Holstein steers (32 months old) on day 4 post slaughter were vacuum-packed and subjected to pressurization at 300 and 500 MPa for 180 s at $15^{\circ}C{\pm}2^{\circ}C$. The samples were then stored for 4 weeks at $5^{\circ}C{\pm}0.5^{\circ}C$ under vacuum and compared with the control (0.1 MPa). Results: HPP increased the shear force value, promoted moisture loss and lipid oxidation, induced surface paleness, stabilized pH during aging, and reduced bacterial load and growth. The shear force value of 500 MPa-treated samples remained higher than the control after aging, while no significant differences were found between the control and 300 MPa-treated samples. Degradation of inosinic acid and inosine occurred during pressurization, resulting in an increase in hypoxanthine content. However, the degradation rate in HPP-treated samples during aging was slower; therefore, inosinic acid and inosine content remained higher than in control samples. No significant differences were found in hypoxanthine content at the end of aging. HPP intensified the levels of hexanal, octanal, 2-methylbutanal, 3-methylbutanal, benzaldehyde, and 2,5-dimethylpyrazine in cooked-aged beef samples. Conclusion: HPP induced aroma development and delayed the degradation of inosinic acid. However, it also reduced the postmortem tenderization rate.

• Asian-Australasian Journal of Animal Sciences
• /
• v.30 no.7
• /
• pp.950-956
• /
• 2017

Objective: Effects of newly isolated Lactobacillus plantarum on the fermentation and chemical composition of fresh rice straw silage was evaluated in this study. Methods: Lactic acid bacteria (LAB) from good crop silage were screened by growing them in MRS broth and a minimal medium with low carbohydrate content. Selected LAB (LAB 1821) were Gram-positive, rods, catalase negative, and were identified to be Lactobacillus plantarum based on their biochemical characteristics and a 16S rRNA analysis. Fresh rice straw was ensiled with two isolated LAB (1821 and 1841), two commercial inoculants (HM/F and P1132) and no additive as a control. Results: After 2 months of storage at ambient temperature, rice straw silages treated with additives were well-preserved, the pH values and butyric and acetic acid contents were lower, and the lactic acid content and lactic/acetic acid ratio were higher than those in the control (p<0.05). Acidity (pH) was lowest, and lactic acid highest, in 1821-treated silage (p<0.05). The $NH_3-N$ content decreased significantly in inoculant-treated silage (p<0.05) and the $NH_3-N$ content in 1821-treated silage was lowest among the treatments. The dry matter (DM) content of the control silage was lower than that of fresh rice straw (p<0.05), while that of the 1841- and p1174-inoculant-treated silages was significantly higher than that of HM/F-treated silage. Microbial additives did not have any significant (p>0.05) effect on acid detergent fiber or neutral detergent fiber contents. Crude protein (CP) content and in vitro DM digestibility (IVDMD) increased after inoculation of LAB 1821 (p<0.05). Conclusion: LAB 1821 increased the CP, IVDMD, lactic acid content and ratio of lactic acid to acetic acid in rice straw silage and decreased the pH, acetic acid, $NH_3-N$, and butyric acid contents. Therefore, adding LAB 1821 improved the fermentation quality and feed value of rice straw silage.

• Asian-Australasian Journal of Animal Sciences
• /
• v.33 no.8
• /
• pp.1265-1272
• /
• 2020

Objective: To evaluate the effect of feeding acidified milk on the growth and fecal microbial diversity of dairy calves. Methods: Twenty healthy 3-day-old female Holstein calves with similar body weights were selected and randomly divided into two groups. One group was fed pasteurized milk (PM, Control), while the other was fed acidified milk (AM) ad libitum until weaned (day 60). The experiment lasted until day 180. Results: There was no difference in the nutritional components between PM and AM. The numbers of Escherichia coli and total bacteria in AM were lower than in PM. At 31 to 40 and 41 to 50 days of age, the milk intake of calves fed AM was higher than that of calves fed PM (p<0.05), and the solid feed intake of calves fed AM was higher than that of calves fed PM at 61 to 90 days (p<0.05). The average daily gain of calves fed AM was also higher than that of calves fed PM at 31 to 60, 61 to 180, and 7 to 180 days (p<0.05). The calves fed AM tended to have a lower diarrhea rate than those fed PM (p = 0.059). Bacteroides had the highest abundance in the feces of calves fed AM on day 50, while Ruminococcaceae_UCG_005 had the highest abundance in the feces of calves fed AM on day 90 and calves fed PM on days 50 and 90. At the taxonomic level, the linear discriminant analysis scores of 27 microorganisms in the feces of calves fed AM and PM on days 50 and 90 were higher than 4.0. Conclusion: Feeding AM increased calf average daily gain and affected fecal bacterial diversity.

• Korean Journal of Microbiology
• /
• v.46 no.3
• /
• pp.248-254
• /
• 2010

To define the optimum conditions for the mass production of four antifungal Pseudomonas spp. isolated from soil, we have investigated culture conditions and effects of various nutrient sources on the bacterial growth and evaluated antagonistic activity against Rhizoctonia solani and Sclerotinia homoeocarpa, plant pathogens. The optimum temperature and pH for the growth of these isolates were determined as pH 7.0 and $20^{\circ}$ or $25^{\circ}C$, respectively. Sucrose, tryptone, and $K_2HPO_4$ generally were more adequate for better growth as carbon, nitrogen and mineral source, respectively. The nutrient sources were also found to be very effective for high antifungal activities against R. solani and S. homoeocarpa. It was elucidated that YUD-F group (P. mandelii and P. fluorescens), which inhabit regions at relatively low temperature, had more broad spectrum and higher antifungal activity than YUD-O group (P. trivialis and P. jessenii) generally against R. solani and S. homoeocarpa. It is thought that the differences of the average temperature in the various habitats of Pseudomonas spp. influence the optimal growth temperature and antifungal activity. Especially, Pseudomonas spp. of YUD-O group showed the better antifungal activity against dollar spot caused by S. homoeocarpa, but showed relatively weaker antifungal activity against brown patch caused by R. solani.

• 한국균학회소식:학술대회논문집
• /
• 2018.05a
• /
• pp.44-44
• /
• 2018

Fusarium head blight (FHB) caused by infection with Fusarium graminearum leads to enormous losses to crop growers, and may contaminate grains with a number of Fusarium mycotoxins that pose serious risks to human and animal health. Antagonistic bacteria that are used to prevent FHB offer attractive alternatives or supplements to synthetic fungicides for controlling FHB without the negative effects of chemical management. Out of 500 bacterial strains isolated from soil, Bacillus amyloliquefaciens JCK-12 showed strong antifungal activity and was considered a potential source for control strategies to reduce FHB. B. amyloliquefaciens JCK-12 produces several cyclic lipopeptides (CLPs) including iturin A, fengycin, and surfactin. Iturin A inhibits spore germination of F. graminearum. Fengycin or surfactin alone did not display any inhibitory activity against spore germination at concentrations less than 30 ug/ml, but a mixture of iturin A, fengycin, and surfactin showed a remarkable synergistic inhibitory effect on F. graminearum spore germination. The fermentation broth and formulation of B. amyloliquefaciens JCK-12 strain reduced the disease incidence of FHB in wheat. Furthermore, co-application of B. amyloliquefaciens JCK-12 and chemical fungicides resulted in synergistic in vitro antifungal effects and significant disease control efficacy against FHB under greenhouse and field conditions, suggesting that B. amyloliquefaciens JCK-12 has a strong chemosensitizing effect. The synergistic antifungal effect of B. amyloliquefaciens JCK-12 and chemical fungicides in combination may result from the cell wall damage and altered cell membrane permeability in the phytopathogenic fungi caused by the CLP mixtures and subsequent increased sensitivity of F. graminearum to fungicides. In addition, B. amyloliquefaciens JCK-12 showed the potential to reduce trichothecenes mycotoxin production. The results of this study indicate that B. amyloliquefaciens JCK-12 could be used as an available biocontrol agent or as a chemosensitizer to chemical fungicides for controlling FHB disease and as a strategy for preventing the contamination of harvested crops with mycotoxins.