• Korean Journal of Food Science and Technology
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• v.36 no.6
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• pp.1020-1025
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• 2004

In previous paper, contaminations of food-borne pathogenic bacteria of Saengshik was found to occur during processing, because detection rates of food-borne pathogenic bacteria in final products were higher than those of raw materials. In this study, methods to reduce food-borne pathogenic bacteria and improved manufacturing process were developed for microbial safety of Saengshik. Food-borne pathogenic bacteria in raw materials were reduced to about 0.5-2.0 log cfu/g when seven kinds of raw materials were washed with electrolyzed water and ozonated water, but food-borne pathogenic bacteria could not be removed completely. After improvement of manufacturing process, numbers of food-borne pathogenic bacteria were same or decreased to levels of raw materials. Gaseous ozone and Biocon could control air-borne bacteria under $1{\times}10^1$ cfu/1000 L of air in pulverization and mixing rooms.

• Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.40-48
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• 2022

Seahorses, which have been cultivated since the 2000s, are economically very important. Gas bubble disease (GBD) is a significant concern in the cultivation of seahorses; therefore, this study aimed to determine the cause of GBD-induced death in two species of Syngnathidae (Syngnathus schlegeli and Hippocampus haema). Rod-shaped bacteria were observed histopathologically and identified as Vibrio splendidus by conventional and real-time PCR analyses. The lethality of V. splendidus varies depending on the host's immune status, and the disease can be prevented through water quality management or improvement of the breeding environment. In this study, the GBD lesions (gas bubbles) were observed at 12℃, 8.0 mg/L of dissolved oxygen, 30 ppt of salinity, and pH 7.7. In addition, rod-shaped bacteria, infiltration of inflammatory cells, and extensive serous exudate were confirmed in the lesions where gas bubbles were found. PCR analysis was able to detect V. splendidus, possibly a secondary infection of the immunocompromised syngnathid fish. Understanding the risk of immunity control and the correlation between these lesions and causal agents will be of great help to the aquaculture industry and the ornamental fish market.

• Journal of Marine Bioscience and Biotechnology
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• v.13 no.1
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• pp.10-19
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• 2021

This study investigated how ozone treatment can successfully inactivate pathogenic bacteria in both artificial seawater and effluents discharged from the fishery quarantine station in Pyeongtaek Port, Korea. Vibrio sp. and Streptococcus sp. were initially inoculated into the artificial seawater. All microbes were almost completely inactivated within 10 min and 30 min by injecting 6.4 mg/min and 2.0 mg/min of ozone, respectively. It was discovered that the water storing Pleuronichthys, Pelteobagrus, and Cyprinus imported from China contained the indicator bacteria, Vibrio sp., Enterococcus sp., total coliforms, and heterotrophic microorganisms. Compared to the control, three indicator bacteria were detected at two to six times higher concentrations. The water samples displayed a diverse microbial community, comprising the following four phyla: Bacteroidetes, Proteobacteria, Firmicutes, and Actinobacteria. Almost all indicator bacteria were inactivated in 5 min at 2.0 mg/min of ozonation; comparatively, 92.9%-98.2% of the less heterotrophic microorganisms were deactivated within the same time period. By increasing the dosage to 6.4 mg/min, 100% deactivation was achieved after 10 min. Despite the almost complete inactivation of most indicator bacteria at high doses after 10 min, several bacterial strains belonging to the Proteobacteria have still been found to be resistant under the given operational conditions.

• Fisheries and Aquatic Sciences
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• v.3 no.3_4
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• pp.217-221
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• 2000

In previous study, marine actinomycetes producing the antibiotics were investigated to invent new antibiotics from east coast of Korea. The optimum growth conditions of Streptomyces sp. NS 13239 were $28^{\circ}C$, pH 7.0 and $3\%$ of NaCl concentration in various media. Streptomyces sp. NS 13239 showed strong antimicrobial activity against gram-positive bacteria, specially Methicillin resistant Staphylococcus aureus (MRSA), but just weak antimicrobial activity against yeasts and mold. On the other hand, it did not show antimicrobial activity against gram-negative bacteria. The optimum conditions for producing antibiotics were almost consistent with optimum growth conditions except carbon source and nitrogen source.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.147-148
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• 2001

Many people living in Asia countries, particularly Korea, Japan and China, have consumed very widely fresh seafood products, such as shrimps, oysters, mussels and other marine invertebrates and fishes, without any heating or cooking. A variety of Vibrio spp., including V. parahaemolyticus, V. cholera. V. vulnificus, and V. fluvialis, lives in these seafoods and cause great problems associated with human disease. A strong antimicrobial agent to effectively inhibit the growth of these pathogenic bacteria in in vivo or in vitro is urgently need for preventing fish and human diseases. (omitted)

• Nutrition Research and Practice
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• v.6 no.3
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• pp.187-194
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• 2012

In this study, the antibacterial effect was evaluated to determine the benefits of high speed drying (HSD) and far-infrared radiation drying (FIR) compared to the freeze drying (FD) method. Citrus press-cakes (CPCs) are released as a by-product in the citrus processing industry. Previous studies have shown that the HSD and FIR drying methods are much more economical for drying time and mass drying than those of FD, even though FD is the most qualified drying method. The disk diffusion assay was conducted, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined with methanol extracts of the dried CPCs against 11 fish and five food-related pathogenic bacteria. The disk diffusion results indicated that the CPCs dried by HSD, FIR, and FD prevented growth of all tested bacteria almost identically. The MIC and MBC results showed a range from 0.5-8.0 mg/mL and 1.0-16.0 mg/mL respectively. Scanning electron microscopy indicated that the extracts changed the morphology of the bacteria cell wall, leading to destruction. These results suggest that CPCs dried by HSD and FIR showed strong antibacterial activity against pathogenic bacteria and are more useful drying methods than that of the classic FD method in CPCs utilization.

• Ocean and Polar Research
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• v.39 no.4
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• pp.245-255
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• 2017

There are a number of pieces of evidences that suggest a link between marine diatoms and microorganisms, but knowledge about related microbial communities is greatly lacking. The present study investigated the microbial community structures related to the growth of the marine diatom Cyclotella meneghiniana. We collected free-living bacteria (FLB) and particle-associated bacteria (PAB) at each growth stage (e.g., lag, exponential, stationary and death) of the diatom, and analyzed their bacterial 16S rDNA using pyrosequencing. Metagenomics analysis showed that community structures of FLB and PAB differed considerably with the progress of growth stages. FLB showed higher diversity than PAB, but variation in the different growth stages of C. meneghiniana was more evident in PAB. The proportion of the genus Hoeflea, belonging to the order Rhizobiales, was dominant in both FLB and PAB, and it gradually increased with the growth of C. meneghiniana. However, Enhydrobacter clade tended to considerably decrease in PAB. In addition, Marinobacter decreased steadily in FLB, but first increased and then decreased in PAB. These results suggest that Hoeflea, Enhydrobacter, and Marinobacter may be closely related to the growth of diatom C. meneghiniana.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.397-403
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• 2018

We determined the resistance rates of pathogenic bacteria isolated from cultured olive flounder Paralichthys olivaceus to erythromycin (Em), antibiotic typically used in aquaculture and analyzed the genotypes of resistant bacteria using polymerase chain reaction (PCR). We isolated and utilized 160 isolates of Streptococcus parauberis, 1 of S. iniae, 66 of Edwardsiella tarda, 56 of Vibrio sp. and 23 of unidentified bacteria from presumed infected olive flounder from Jeju Island from March 2016 to October 2017. Of the 306 isolated strains, Em-resistant strains included 33 of S. parauberis, 39 of E. tarda and 2 of Vibrio sp. We conducted PCR to assess the resistance determination of Em-resistant strains. Five different types of Em-resistance genes were detected in the 74 Em-resistant strains: erm (A), erm (B), erm (C), mef (A) and mef (E); erm (A) and erm (B) were detected in 1 (3%) and 24 (72.7%) S. parauberis isolates, respectively. In E. tarda, erm (B) was detected in five isolates (12.8 %) and no Em-resistance genes were detected in the two Vibrio sp. isolates.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.389-396
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• 2018

Marine pathogenic bacteria, such as Streptococcus parauberis, Edwardsiella tarda and Vibrio harveyi, can cause lethal infections in farmed fish, ozone and antibiotics, are employed to sterilize waters used for rearing fish to mitigate this threat. The most widely used method is treatment with sodium hypochlorite solution. However, the maintenance of a constant concentration of chlorine in rearing waters can be difficult. We investigated the potential of a mixed oxidant (MO) solution generated by electrolysis of sea water to improve water quality. We measured the survival rates of fish pathogenic bacteria exposed to different concentrations of MO (0.5, 1.0, 1.5 and 2.0 MO) and sodium hypochlorite (0.5, 1.0, 1.5 and 2.0 ppm) for various lengths of time (0, 5, 10, 15, 20, 25 and 30 min). We found a time-dependent decrease in the survival rates of the tested pathogenic microorganisms. The sterilization effect of the MO solution on pathogenic organisms was greater than that of sodium hypochlorite for gram-negative and gram-positive bacteria. We conclude that MO solution produced by electrolysis could be used to maintain a constant chlorine concentration in aquaculture systems.

• Korean Journal of Microbiology
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• v.48 no.4
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• pp.328-331
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• 2012

Microbial diversity in the 1500 m depth sea waters off the coast of Ulleung island of the East Sea, Korea, was investigated. Genomic DNAs were extracted directly from the marine microbes filtered through ultramembrane filters. Pyrosequencing of 16S rDNAs of these microbes resulted in 13,029 reads, of which uncultured bacteria consisted of 54.1%, alphaproteobacteria 23.4%, and gammaproteobacteria 22.3%. Other classes such as flavobacteria, actinobacteria, and epsilonproteobacteria were distributed within 0.2% of total reads. Among the cultivable bacteria, it was found that Rhodobacteraceae family of alphaproteobacteria, Alteromonadaceae, Halomonadaceae, and Piscirickettsiaceae families of gammaproteobacteria were mostly distributed in the deep-sea waters.