• Korean Journal of Food Science and Technology
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• v.36 no.3
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• pp.501-506
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• 2004

Microflora and contamination process of Saengshik products were investigated to ensure microbial safety of Saengshik. Food-borne pathogenic bacteria, such as Staphylococcus aureus, Bacillus cereus, and Clostridium perfringens detected mainly from grains were not removed by washing with tap water and freeze-drying. Contaminations of food-borne pathogenic bacteria occurred through raw material powder processed at other factories and during actual product manufacturing process, because detection rates of final products were higher than those of raw materials. Concentration of food-borne pathogenic bacteria increased with advancing of process after first pulverization. Dusts of powder and powder attached to machine were good media for air-borne microorganisms and caused to increase of food-borne pathogenic bacteria during process. Improvement of manufacturing process and sanitary control of machines arc necessary to ensure microbial safety of Saengshik.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.1
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• pp.100-110
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• 2020

Objective: The objective of this study was to isolate proteolytic microorganisms and evaluate their effects on proteolysis in total mixed ration (TMR) silages of soybean curd residue. Methods: TMRs were formulated with soybean curd residue, alfalfa or Leymus chinensis hay, corn meal, soybean meal, a vitamin-mineral supplement, and salt in a ratio of 25.0: 40.0:30.0:4.0:0.5:0.5, respectively, on a basis of dry matter. The microbial proteinases during ensiling were characterized, the dominate strains associated with proteolysis were identified, and their enzymatic characterization were evaluated in alfalfa (A-TMR) and Leymus chinensis (L-TMR) TMR silages containing soybean curd residue. Results: Both A-TMR and L-TMR silages were well preserved, with low pH and high lactic acid concentrations. The aerobic bacteria and yeast counts in both TMR silages decreased to about 10⁵ cfu/g fresh matter (FM) and below the detection limit, respectively. The lactic acid bacteria count increased to 10⁹ cfu/g FM. The total microbial proteinases activities reached their maximums during the early ensiling stage and then reduced in both TMR silages with fermentation prolonged. Metalloproteinase was the main proteinase when the total proteinases activities reached their maximums, and when ensiling terminated, metallo and serine proteinases played equally important parts in proteolysis in both TMR silages. Strains in the genera Curtobacterium and Paenibacillus were identified as the most dominant proteolytic bacteria in A-TMR and L-TMR, respectively, and both their proteinases were mainly with metalloproteinase characteristics. In the latter ensiling phase, Enterococcus faecium strains became the major sources of proteolytic enzymes in both TMR silages. Their proteinases were mainly of metallo and serine proteinases classes in this experiment. Conclusion: Proteolytic aerobic bacteria were substituted by proteolytic lactic acid bacteria during ensiling, and the microbial serine and metallo proteinases in these strains played leading roles in proteolysis in TMR silages.

• Journal of Microbiology and Biotechnology
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• v.27 no.11
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• pp.2019-2027
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• 2017

Recently, cabbage kimchi has occasionally been associated with the foodborne diseases of enteric viruses such as human norovirus (HuNoV). This study aimed to evaluate the correlation between microbial/physicochemical properties and persistence of HuNoV in experimentally contaminated cabbage kimchi fermented and stored at $4^{\circ}C$ or $10^{\circ}C$ for 28 days. Changes in organic acid content, lactic acid bacteria (LAB), acidity, pH, and salinity were analyzed. The recovery of structurally intact HuNoV was examined for up to 28 days post-inoculation, using a NoV GII.4 monoclonal antibody-conjugated immuno-magnetic separation method combined with quantitative real-time reverse transcription polymerase chain reaction. On day 0, LAB loads were $4.70log_{10}$ colony forming units/g and HuNoV GII.4 titers were $2.57log_{10}\;genomic\;copies/{\mu}l$, at both temperatures. After 28 days, intact HuNoV titers decreased to 1.58 ($4^{\circ}C$) and $1.04(10^{\circ}C)log_{10}\;genomic\;copies/{\mu}l$, whereas the LAB density increased. This correlated with a gradual increase in lactic acid and acetic acid at both temperatures. Our findings support a statistical correlation between changes in physicochemical properties and the recovery of structurally intact HuNoV GII.4. Moreover, we determined that the production of organic acid and low pH could affect HuNoV GII.4 titers in cabbage kimchi during fermentation. However, HuNoV GII.4 was not completely eliminated by microbial/physicochemical factors during fermentation, although HuNoV GII.4 was reduced. Based on this, we speculate that the persistence of HuNoV GII.4 may be affected by the continually changing conditions during kimchi fermentation.

• Journal of Life Science
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• v.24 no.1
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• pp.54-60
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• 2014

Aromatic hydrocarbons are toxic environmental pollutants that are detrimental to the ecosystem and human health. Among them, chlorotoluene and nitrotoluene are toxic to hydrobios and irritate the skin, eyes, and respiratory organs of humans. We herein report the development of recombinant microbial biosensors for cheap and rapid monitoring of chlorotoluene and nitrotoluene compounds. Plasmids were constructed by inserting the xylR regulatory gene for BTEX (benzene, toluene, ethylbenzene, and xylene) degradation into upstream of Po' (the DmpR activator promoter Po with the deletion of its own upstream activating sequences) or Pu (the cognate promoter of XylR)::lacZ (the ${\beta}$-galactosidase gene) and transformed into Escherichia coli $DH5{\alpha}$. In the presence of inducers, the biosensor cells immobilized in agarose developed a red color in 1-2 h due to the hydrolysis of chlorophenol red ${\beta}$-D-galactopyranoside (CPRG), a substrate of ${\beta}$-galactosidase that was expressed by the inducers. Among BTEX, high responses were specifically observed with o-, m-, p-chlorotoluene ($0.1{\mu}M-100 mM$) and o-, m-, p-nitrotoluene (0.1 mM-100 mM). Po' demonstrated higher responses than those with Pu. The biosensors immobilized in agarose showed good stability after 21 days' storage at $4^{\circ}C$, and responses in untreated wastewater spiked with chlorotoluene and nitrotoluene, suggesting they can be used to detect compounds in wastewater.

• Food Science and Preservation
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• v.15 no.4
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• pp.606-611
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• 2008

Myungran Jeotkal, Korean fermented seafood, and its ingredients(hot red pepper powder, ginger, garlic, and seasoning mix) were irradiated with 0, 0.5, 1.0, 2.0, and 5.0 kGy of gamma rays and stored at 4C for 4 weeks to determine changes in microbiological and sensory characteristics. Water activities of Myungran Jeotkal, hot red pepper powder, ginger, garlic, and seasoning mix were 0.89 0.56, 0.98, 0.99, and 0.07, respectively. Myungran Jeotkal was observed to be initially contaminated. Total aerobic bacteria, yeast and mold, and coliform levels were 6.7, 4.3, and 3.6 log CFU/g, respectively. Irradiation at 2 kGy afforded approximately a 4 log reduction in total aerobic bacteria, and a 3 log drop in both yeast and mold levels and coliform bacteria(P<0.05). No viable microbial cells were detected in Myungran Jeotkal after 5 kGy of irradiation(at a detection limit of 101 CFU/g). The total aerobic bacterial level in red pepper powder was 6.3 log CFU/g and this component, of the tested ingredients, contributed most to the microbial contamination of Myungran Jeotkal. The initial count of total aerobic bacteria, 6.3 log CFU/g, was significantly reduced to 4.5 log CFU/g after irradiation(P<0.05). Sensory evaluation showed that gamma irradiation of up to 5.0 kGy did not adversely affect overall acceptability of Myungran Jeotkal or its ingredients during cold storage. Therefore, gamma irradiationwas effective to extend the shelf-life of Myungran Jeotkal.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.4
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• pp.179-185
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• 2005

Polycyclic aromatic hydrocarbons (PAHs) are a kind of toxic environmental pollutants and has been accumulated usually in marine sediments. Due to their potential hazardous to human, removal of PAHs from environments has been great concern. In the present study, the effect of microbial inoculation and the supplementation of mixed form cyclodextrin (M-CD) was assessed in the pre-sterilized or nonsterilized microcosms for optimizing operational conditions for ex situ bioremediation of sediments contaminated by PAHs. Activity of electron transport system (ETSA) was increased by the addition of M-CD regardless of inoculation of microorganisms in microcosms without sterilization. The degradation rate of PAHs in sterilized microcosms was app. 9-20% by the inoculation of single strain and 24-37% by the inoculation of microbial consortium supplemented with 1% M-CD, respectively. The degradation was not observed in microcosms without sterilization under the same conditions. The proportion of inoculated microorganisms also decreased in nonsterilized microcosms. Signals of inoculated bacteria were decreased to detection limit after 2 days in the microcosms without M-CD. In conclusion, microbial inoculation with appropriate carbon sources and removal of natural flora and grazers are required for the efficient ex situ bioremediation of sediments contaminated by PAHs in bioslurry reactor.

• Food Science of Animal Resources
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• v.36 no.4
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• pp.463-468
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• 2016

Contamination by foodborne pathogens and mycotoxins was examined in 475 eggs and 20 feed samples collected from three egg layer farms, three egg-processing units, and five retail markets in Korea. Microbial contamination with Salmonella species, Escherichia coli, and Arcobacter species was examined by bacterial culture and multiplex polymerase chain reaction (PCR). The contamination levels of aflatoxins, ochratoxins, and zearalenone in eggs and chicken feeds were simultaneously analyzed with high-performance liquid chromatography coupled with fluorescence detection after the post-derivatization. While E. coli was isolated from 9.1% of eggs, Salmonella species were not isolated. Arcobacter species were detected in 0.8% of eggs collected from egg layers by PCR only. While aflatoxins, ochratoxins, and zearalenone were found in 100%, 100%, and 85% of chicken feeds, their contamination levels were below the maximum acceptable levels (1.86, 2.24, and 147.53 μg/kg, respectively). However, no eggs were contaminated with aflatoxins, ochratoxins, or zearalenone. Therefore, the risk of contamination by mycotoxins and microbes in eggs and chicken feeds is considered negligible and unlikely to pose a threat to human health.

• Restorative Dentistry and Endodontics
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• v.27 no.1
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• pp.54-65
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• 2002

Black-pigmented bacteria have been implicated in the endodontic infections. This group of microorganisms includes Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens. The organisms display a wide variety of virulence factors that may be pertinent to acute endodontic infections. The aim of this study was to identify P. endodontalis, P. gingivalis, P. intermedia, and P. nigrescens by using special potency disk test, filter paper spot test, 165 rRNA gene-directed PCR, and API 32A. Microbial samples were collected from root canals of 33 intact teeth with necrotic pulp and/or apical periodontitis. Conventional laboratory methods were used for identification of the strains of black pigmented bacteria. Eighteen of 33 samples were positive for the growth of black-pigmented bacteria Five colonies were cultured from each pure cultured colonies from Brucella agar plate. Seventy seven colonies were positive for the growth of black-pigmented bacteria. Thirty three of 77(42.6%) were identifed as P. nigrescens, 10 of 77(12.9%)were P. gingivalis, 6 of 77(7.8%) were P. endodontalis, 10 of 77(12.9%) were P. intermedia. On the contrary the reference strains of P. nigrescens, experimental strains of P nigrescens was sensitive to kanamycin in special potency disk test. 165 rRNA gene PCR and API test after rapid presumptative identification methods, such as special potency disk test and filter paper spot test, would be accurate detection methods for black-pigemented bacteria.

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.171-171
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• 2008

We monitored the occurrence of human enteric viruses in urban rivers by cell culture-PCR and RT-nested PCR. Water samples were collected monthly or semimonthly between May 2002 and March 2003 in four urban tributaries. Enteric viruses were detected by RT-nested PCR and cell culture-PCR based on a combination of Buffalo Green monkey kidney (BGMK) and A549 cell lines, followed by phylogenetic analysis of amplicons. By RT-nested PCR analysis, 45 (77.6%), 32 (55.2%), 32 (55.2%), 26 (44.8%), 12 (20.7%), 2 (3.4%), 4 (6.9%), and 4 (6.9%) of 58 samples showed positive results with adenoviruses, enteroviruses, noroviruses (NV) genogroup I (GI) and II (GII), reoviruses, hepatitis A viruses, rotaviruses and sapoviruses, respectively. Adenoviruses were most often detected and only eight (13.8%) samples were negative for adenoviruses and positive for other enteric viruses in the studied sites. Thirty-one (77.5%) of the 40 samples were positive for infectious adenoviruses and/or enteroviruses based on cell culture-PCR, and the frequency of positive samples grown on A549 and BGMK (65.0%) was higher than that grown on BGMK alone (47.5%). The occurrence of each enteric virus, except reoviruses and hepatitis A viruses was not statistically correlated with the water temperature and levels of fecal coliforms according to Binary logistic regression model. By sequence analysis, most strains of adenoviruses and enteroviruses detected in this study are similar to the causative agent of viral diseases in Korea and most NV GI- and GII-grouped strains were closely related to the reference strains from China and Japan, and GII/4-related strains had similar sequences to strains recognized as a worldwide epidemic outbreak. Our results suggested that monitoring human enteric viruses is necessary to improve microbial quality and cell culture-PCR using the combination of A549 and BGMK cells and the adenovirus detection by PCR could be useful for monitoring viral contamination in the aquatic environment.

• Microbiology and Biotechnology Letters
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• v.42 no.2
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• pp.121-130
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• 2014

Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis was adopted to explore rapid differentiation in the diversity and dynamics of bacteria in kimchi made in Korea and China for future application in kimchi origin discrimination. T-RFLP analysis supported the reproducible and rapid detection of major lactic acid bacteria known to be involved in kimchi fermentation. The taxonomic resolution level of this T-RFLP analysis was between the species and genus level, but was not specific enough for the detection of a bacterium found only in one origin, either Korea or China. The bacterial community structure successions in kimchi samples from Korea and China analyzed by T-RFLP analysis occurred with a similar pattern. Bacillus spp. which were not detected in the early microbial studies of kimchi were constantly detected until the late fermentation stage of kimchi in our T-RFLP analysis and their existence was proved by culture-based identification. Additionally, sporulation of Bacillus spp. during kimchi fermentation was discovered.