• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.337-337
• /
• 2011

Application of plasma technology on microbial sterilization has been frequently studied. In spite of accumulating number of studies, many have been focused on bacteria. Reports on eukaryotic yeasts and filamentous fungi are limited. In addition, mechanism of plasma effect still needs to be clarified. In this study, we analyzed the effect of non-thermal atmospheric pressure plasma on the budding yeast, Saccharomyces cerevisiae using DBD-type device. When yeast cells were exposed to plasma (at 2 mm distance) and then cultured on YPD-agar plate, number of cells survived (shown as colony) were reduced proportionally to exposure time. More than 50% reduction in number of colonies were observed after twice exposure of 5min. each. Colonies much smaller than those of control (no plasma exposure) were appeared after twice exposure of 5 min. each. It seems that small colonies are resulted from delayed cell growth due to the damage caused by plasma treatment. Microscopic analysis demonstrates that yeast cells treated with plasma for 5 min. twice have more rough and shrinked shape compared to oval shape with smooth surface of control.

• Journal of Dental Anesthesia and Pain Medicine
• /
• v.16 no.1
• /
• pp.17-24
• /
• 2016

Background: To evaluate the antimicrobial activity of lidocaine (LD) topical anesthetic spray against oral microflora. Methods: Antimicrobial effects of 10% LD spray were assessed against six bacterial cultures obtained from volunteers: Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, Streptococcus salivarius, Streptococcus pyogenes, and Streptococcus sanguinis. The filter papers contained $50-{\mu}l$ LD, brain heart infusion (BHI) broth, or 0.2% chlorhexidine. Papers were placed on the cultured blood plates for 1-3 min. After the papers were removed, plates were incubated for 24 h. Bacterial growth on the contact areas was recorded as the antimicrobial score. The split mouth technique was use in for sample collection in clinical study. Filter papers soaked with either BHI broth or LD were placed on the right or left buccal mucosa for 1 min, and replaced with other papers to imprint biofilms onto the contact areas. Papers were placed on blood plates, incubated for 24 h, and antimicrobial scores were determined. Experiments were conducted for 2- and 3-min exposure times with a 1-day washout period. Results: LD exhibited bactericidal effects against E. coli, S. sanguinis, and S. salivarius within 1 min but displayed no effect against S. aureus, E. faecalis, and S. pyogenes. The antimicrobial effect of LD on oral microflora depended upon exposure time, similar to the results obtained from the clinical study (P < 0.05). LD showed 60-95% biofilm reduction on buccal mucosa. Conclusions: Antimicrobial activity of 10% LD topical anesthetic spray was increased by exposure time. The 3 min application reduced oral microflora in the buccal mucosa.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.2
• /
• pp.234-243
• /
• 2007

Vibrio vulnificus is an opportunistic pathogen that causes septicemia in humans. To identify the genes associated with its pathogenicity, in vivo expression technology (IVET) was used to select genes specifically expressed in a host, yet not significantly in vitro. Random lacZ-fusions in the genome of V vulnificus strain MO6-24/O were constructed using an IVET vector, pSG3, which is a suicide vector containing promoterless-aph and -lacZ as reporter genes. A total of ${\sim}18,000$ resulting library clones were then intraperitoneally injected into BALB/c mice using a colony forming unit (CFU) of $1.6{\times}10^6$. Two hours after infection, kanamycin was administered at $200{mu}g$ per gram of mouse weight. After two selection cycles, 11 genes were eventually isolated, which were expressed only in the host. Among these genes, VV20781 and VV21007 exhibiting a homology to a hemagglutinin gene and tolC, respectively, were selected based on having the highest frequency. When compared to wild-type cells, mutants with lesions in these genes showed no difference in the rate of growth rate, yet a significant decrease in cytotoxicity and the capability to form a biofilm.

• Journal of Microbiology and Biotechnology
• /
• v.32 no.10
• /
• pp.1315-1324
• /
• 2022

Fermentation is an effective process for providing various beneficial effects in functional beverages. Lactic acid bacteria and yeast fermentation-based biotransformation contribute to enhancement of nutritional value and digestibility, including lactose intolerance reduction and control of infections. In this study, the probiotic fermented fruit juice (PFJ) was produced by Lactobacillus plantarum TISTR 1465, Lactobacillus salivarius TISTR 1112, and Saccharomyces boulardii CNCM I-745 while mixed fruit juice (MFJ) was used as the basic medium for microorganism growth. The potential function, the anti-salmonella activity of PFJ, was found to be effective at 250 mg/ml of MIC and 500 mg/ml of MBC. Biofilm inhibition was performed using the PFJ samples and showed at least 70% reduction in cell attachment at the MIC concentration of Salmonella Typhi DMST 22842. The antioxidant activities of PFJ were determined and the results revealed that FSB.25 exhibited 78.40 ± 0.51 mM TE/ml by FRAP assay, while FPSB.25 exhibited 3.44 ± 0.10 mM TE/ml by DPPH assay. The volatile compounds of PFJ were characterized by GC-MS, which identified alcohol, aldehyde, acid, ester, ketone, phenol, and terpene. The most abundant organic acid and alcohol detected in PFJ were acetic acid and 2-phenylethanol, and the most represented terpene was β-damascenone. The sensory attributes showed scores higher than 7 on a 9-point hedonic scale for the FPB.25, illustrating that it was well accepted by panelists. Taken together, our results showed that PFJ could meet current consumer demand regarding natural and functional, fruit-based fermented beverages.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.9
• /
• pp.1149-1161
• /
• 2023

Changes in the gut microbiome cause recolonization by pathogens and inflammatory responses, leading to the development of intestinal disorders. Probiotics administration has been proposed for many years to reverse the intestinal dysbiosis and to enhance intestinal health. This study aimed to evaluate the inhibitory effects of two newly designed probiotic mixtures, Consti-Biome and Sensi-Biome, on two enteric pathogens Staphylococcus aureus and Escherichia coli that may cause intestinal disorders. Additionally, the study was designed to evaluate whether Consti-Biome and Sensi-Biome could modulate the immune response, produce short-chain fatty acids (SCFAs), and reduce gas production. Consti-Biome and Sensi-Biome showed superior adhesion ratios to HT-29 cells and competitively suppressed pathogen adhesion. Moreover, the probiotic mixtures decreased the levels of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-6 and IL-1β. Cell-free supernatants (CFSs) were used to investigate the inhibitory effects of metabolites on growth and biofilms of pathogens. Consti-Biome and Sensi-Biome CFSs exhibited antimicrobial and anti-biofilm activity, where microscopic analysis confirmed an increase in the number of dead cells and the structural disruption of pathogens. Gas chromatographic analysis of the CFSs revealed their ability to produce SCFAs, including acetic, propionic, and butyric acid. SCFA secretion by probiotics may demonstrate their potential activities against pathogens and gut inflammation. In terms of intestinal symptoms regarding abdominal bloating and discomfort, Consti-Biome and Sensi-Biome also inhibited gas production. Thus, these two probiotic mixtures have great potential to be developed as dietary supplements to alleviate the intestinal disorders.

• Journal of Korean society of Dental Hygiene
• /
• v.21 no.5
• /
• pp.527-533
• /
• 2021

Objectives: Electrolyzed water has been proven to have antibacterial effects against various microorganisms. However, there are only a few studies about effects of electrolyzed water on oral bacteria. The purpose of this study was to examine the antibacterial effect of electrolyzed water on Streptococcus mutans in vitro. Methods: S. mutans KCOM 1054 was treated with electrolyzed water for 1 or 3 minutes and plated on Mitis Salivarius agar with 15% sucrose and bacitracin. After incubation for 48 hours, colony forming units (CFU) were counted, and dental plaque was quantified by crystal violet staining. Results: The growth of S. mutans was significantly inhibited by electrolyzed water (p<0.001). In addition, the dental plaque formation by S. mutans was decreased in a time-dependent manner by exposure to electrolyzed water (p<0.001). Conclusions: Our results suggest that electrolyzed water can effectively prevent dental caries by inhibiting growth of (and the formation of dental plaque by) S. mutans.

• Journal of Korean Academy of Oral Health
• /
• v.41 no.1
• /
• pp.22-27
• /
• 2017

Objectives: Dental plaque is composed of 700 bacterial species. It is known that some oral microorganisms produce porphyrin, and thus, they emit red fluorescence when illuminated with blue light at a specific wavelength of <410 nm. Porphyromonas gingivalis belongs to the genus Porphyromonas, which is characterized by the production of porphyrin. The aim of this study was to evaluate red fluorescence emission of some oral microorganisms interacting with P. gingivalis. Methods: Five bacterial strains (P. gingivalis, Streptococcus mutans, Lactobacillus casei, Actinomyces naeslundii, and Fusobacterium nucleatum) were used for this study. Tryptic soy agar medium supplemented with hemin, vitamin K3, and sheep blood was used as a growth medium. The fluorescence emission of bacterial colonies was evaluated under 405 nm-wavelength blue light using a Quantitative Light-induced Fluorescence Digital (QLF-D) camera system. Each bacterium was cultured alone and co-cultured in close proximity with P. gingivalis. The red/green (R/G) ratio of fluorescence image was calculated and the differences of R/G ratio according to each growth condition were compared using the Mann-Whitney test (P<0.05). Results: Single cultured S. mutans, L. casei and A. naeslundii colonies emitted red fluorescence (R/G ratio=$2.15{\pm}0.06$, $4.31{\pm}0.17$, $5.52{\pm}1.29$, respectively). Fusobacterium nucleatum colonies emitted green fluorescence (R/G ratio=$1.36{\pm}0.06$). The R/G ratios of A. naeslundii and F. nucleatum were increased when P. gingivalis was co-cultured with each bacterium (P<0.05). In contrast, the R/G ratios of S. mutans and L. casei were decreased when P. gingivalis was co-cultured with each bacterium (P=0.002, 0.003). Conclusions: This study confirmed that P. gingivalis could affect the red fluorescence of other oral bacteria under 405 nm-wavelength blue light. Our findings concluded that P. gingivalis has an important role for red fluorescence emission of dental biofilm.

• Journal of Food Hygiene and Safety
• /
• v.23 no.2
• /
• pp.157-162
• /
• 2008

Enterobacter sakazakii was initially referred to as yellow-pigmented Enterobacter cloacae and reclassified in 1980. E. sakazakii infection cause life-threatening meningitis, septicemia, and necrotizing enterocolitis in infants. Powdered infant formula (PIF) and baby foods may be the important vehicle of E. sakazakii infection. It has been reported that E. sakazakii was isolated from PIF and sunsik ingredients produced in Korea. Some infants have been fed sunsik as a weaning diet. Therefore, it is necessary that this organism should be inactivated on preparing PIF and sunsik at homes and in hospitals. The cocktail of three Korean E. sakazakii strains (human, sunsik and soil isolates) were used to investigate the inactivation of this organism with hot water at 50, 60, 65, 70 and $80^{\circ}C$ and microwave heating for 60, 75, 90, 105 and 120 sec. Reconstituted PIF and sunsikwere inoculated with cocktailed vegetative cells of E. sakazakii at 6 log CFU/mL. Thermal inactivation of vegetative cells of E. sakazakii were achieved by reconstituted PIF and sunsik with hot water at $60^{\circ}C$ or greater and with microwave heating at 2,450 MHz for 75 sec or longer. Considering that biofilm formation of E. sakazakii was adapted to survive the dry environment that is PIF and sunsik and thermal resistance increased, it is suggested that inactivation of E. sakazakii was used by hot water at $70^{\circ}C$ or greater and microwave heating for 90 sec or longer. Reconstituted PIF and sunsik were inoculated with cocktailed vegetative cells of E. sakazakii at 2 to 3 log CFU/mL to investigate the growth curve of this organism and stored at 5, 10, 15, 20, 25, 30 and $35^{\circ}C$. Viable counts slightly changed at 5, $10^{\circ}C$ during 48 h but grew at $15^{\circ}C$ or greater. Considering that E. sakazakii is able to grow in infant formula milk at refrigerator temperature, reconstituted PIF and sunsik that are not immediately consumed should be discarded or stored at refrigeration temperatures within 24 h.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.7
• /
• pp.783-792
• /
• 2007

To investigate the effects of alkalinity on the nitrification capability of the nonwoven fabric filter bioreactor(NFBR), an experiment was performed for 641 days at a hydraulic retention time of approximately 11 hours by changing the influent concentration of $NH_3-N$ from 54 mg/L to 1,400 mg/L and alkalinity from 43 mg/L to 10,480 mg/L. The MLSS concentration reduced from an initial value of 2,650 mg/L down to 830 mg/L, then increased up to 8,340 mg/L. Though the volumetric loading rate varied in a range of $0.120\sim3.130$ kg $NH_3-N/m^3-day$, the F/M ratio showed a narrow range of $0.067\sim0.414$ kg $NH_3-N/kg$ MLSS-day. The average nitrification efficiency at each experimental stage resulted in the range of $35.2\sim100%$, and the maximum nitrification rate was 2.970 kg $N/m^3-day$ or 0.489 g N/g MLVSS-day. The nitrifiers' fraction of the MLVSS increased up to 100% from an initial value of 7.1% and the biofilm formed on the nonwoven fabric filter showed a very low nitrifiers' fraction of mere 2.2%. The growth yield of the MLSS and the alkalinity consumption rate were computed to be 0.117 g VSS/g N removed and 7.08 g alkalinity/g $NO_x^--N$ produced, respectively. Results of the research suggest that NFBR could be an adequate process for nitrification of wastewaters with high ammonia concentrations.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.8
• /
• pp.922-929
• /
• 2007

The complete oxidation of ammonia to nitrate is a distinctive two-step process divided into the oxidation of ammonia to nitrite(nitritation) by Nitrosomonas and the oxidation of nitrite to nitrate(nitratation) by Nitrobacter. The nitrogen removal via nitrite accumulation offers several advantages such as saving costs for aeration, saving carbon source and finally reduction of sludge discharge. In this work a suspended bioreactor coupled with membrane filtration(MBR) was used to find the process conditions of nitrite build-up. The MBR enables to reach sufficient nitrifying bacteria in the bioreactor, although the autotrophic bacteria can be easily washed out due to their lower growth rate. The dissolved oxygen concentration $c'_{O2}$ and ammonia concentration $c_{NH3}$ in the reactor were varied and investigated as parameters for nitrite accumulation. As a result the higher ammonia concentration in the reactor is very effective for starting nitrite build-up and the effect was strengthened in combination with lower dissolved oxygen concentration. With lower $c'_{O2}<0.3$ $mgL^{-1}$ $O_2$ and high $c_{NH3}=6.3\sim14.9$ $mgL^{-1}$ $NH_3N$ the 74% of the nitrite accumulation was achieved. Specially, it was found that the nitrite accumulation could occur not only in biofilm reactor as many references showed but also in the membrane bioreactor carried out in this study.