• Journal of Mushroom
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• v.7 no.4
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• pp.168-172
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• 2009

We attempted to isolate the bacterial strains from the fruiting bodies of Agaricus brazilensis and determined their effects on browning and distortions of mushrooms. No bacterial strains were isolated when the middle of browning regions of A. brazilensis were used. Total 125 bacterial strains were obtained from the surface of browning regions and classified into 17 different genera and 29 species by using MIDI methods. Most common genus were Pseudomonas (26), Yersinia (29), and Cedecea (29). High lytic activity were detected when Pseudomonas strains were tested, while relatively low lytic activity were observed with both Yersinia and Cedecea strains.Therefore, we believed the distortion of mushroom could be the result of bacterial infections. Also, the development of brownish color was detected in large number of A. brazilensis strains only by incubation at 4C, suggesting no specific correlation between bacterial strains and brownish color development. Also, it is considered that the development of brownish color can be the normal changes of A. brazilensis.

• Mycobiology
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• v.37 no.1
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• pp.62-66
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• 2009

The internal stipe necrosis of cultivated mushrooms (Agaricus bisporus) is caused by the bacterium Ewingella americana, a species of the Enterobacteriaceae. Recently, Ewingella americana was isolated from cultivated white button mushrooms in Korea evidencing symptoms of internal stipe browning. Its symptoms are visible only at harvest, and appear as a variable browning reaction in the center of the stipes. From these lesions, we isolated one bacterial strain (designated CH4). Inoculation of the bacterial isolate into mushroom sporocarps yielded the characteristic browning symptoms that were distinguishable from those of the bacterial soft rot that is well known to mushroom growers. The results of Gram stain, flagellal staining, and biochemical tests identified these isolates as E. americana. This was verified by pathogenicity, physiological and biochemical characteristics, and the results of an analysis of the 16S rRNA gene sequences and the fatty acids profile. This is the first report of the isolation of E. americana from cultivated white button mushrooms in Korea.

• The Korean Journal of Mycology
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• v.45 no.4
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• pp.370-376
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• 2017

Pseudomonads cause bacterial brown blotch disease, which causes great damage to the common mushroom Agaricus bisporus. The tolerance of A. bisporus to pseudomonads was tested and found to not be correlated with mycelium growth ability. The offsprings of the tolerant strain (ASI1085) to pseudomonads were not as tolerant as their parents in the mycelium stage. But, tolerance decreased compared to mycelium in the fruiting body. The offsprings of the weakly tolerant strain (ASI1321) were even more weak in the mycelium stage. It is presumed that the tolerance of the parents is transferred to later generations. The tolerance in the mycelium was not correlated in the fruiting body. Therefore, the browning of the fruiting body is thought to be induced by other factors. Pseudomonas tolaasii caused higher browning than Pseudomonas agarici. Pseudomonas reactans did not have a significant effect on the mycelium, but affected the browning of the fruit bodies. P. agarici had higher ability to inhibit mycelium growth than fruiting body growth.

• Journal of Life Science
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• v.14 no.3
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• pp.501-508
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• 2004

A bacterial strain CJ-3 which produced chitinase was isolated from Korean traditional soy sauce. Using 16S rDNA analysis, the strain CJ-3 was identified as Bacillus atrophaeus. The approximate molecular weight of the putative chitinase enzyme was 31.0 kDa and the enzyme activity was remarkably induced by addition of colloidal chitin (0.5, 1.0, 2.0%). The antioxidant activity was increased 53% by the browning reaction products of B. atrophneus CJ-3. Escherichia. coli lipopolysaccharides (LPS)-induced production of nitric oxide(NO) was reduced up to 45% by the browning reaction product in RAW264.7 macrophage. Inhibition of cell viability in the presence of LPS was recovered to normal level by the browning reaction product. These results suggest that browning reaction of B. atrophaeus CJ-3 plays an important role for activation of immune system. B. atrophaeus CJ-3 exhibited optimum temperature and pH of 37$^{\circ}C$ and pH 7.0∼8.0, respectively. The major intracelluar free amino acid was determined to be glutamate.

• The Plant Pathology Journal
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• v.34 no.5
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• pp.393-402
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• 2018

Rice world production is affected due to the growing impact of diseases such as bacterial panicle blight, produced by Burkholderia glumae. The pathogen-induced symptoms include seedling rot, grain rot and leafsheath browning in rice plants. It is currently recognized the entrance of this pathogen to the plant, from infected seeds and from environmental sources of the microorganism. However, it is still not fully elucidated the dynamics and permanence of the pathogen in the plant, from its entry until the development of disease symptoms in seedlings or panicles. In this work it was evaluated the infection of B. glumae rice plants, starting from inoculated seeds and substrates, and its subsequent monitoring after infection. Various organs of the plant during the vegetative stage and until the beginning of the reproductive stage, were evaluated. In both inoculation models, the bacteria was maintained in the plant as an endophyte between $1{\times}10^1$ and $1{\times}10^5cfu$ of B. $glumae.g^{-1}$ of plant throughout the vegetative stage. An increase of bacterial population towards initiation of the panicle was observed, and in the maturity of the grain, an endophyte population was identified in the flag leaf at $1{\times}10^6cfu$ of B. $glumae.g^{-1}$ fresh weight of rice plant, conducting towards the symptoms of bacterial panicle blight. The results found, suggest that B. glumae in rice plants developed from infected seeds or from the substrate, can colonize seedlings, establishing and maintaining a bacterial population over time, using rice plants as habitat to survive endophyticly until formation of bacterial panicle blight symptoms.

• The Plant Pathology Journal
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• v.37 no.2
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• pp.137-151
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• 2021

The present study describes the bacterial blight of walnut, caused by Xanthomonas arboricola pv. juglandis (Xaj) in the northern Gyeongbuk province, Korea. Disease symptoms that appear very similar to anthracnose symptoms were observed in walnut trees in June 2016. Pathogens were isolated from disease infected leaves, fruits, shoots, bud, flower bud of walnut, and cultured onto yeast dextrose carbonate agar plates. Isolated bacteria with bacterial blight symptoms were characterized for their nutrient utilization profiles using Biolog GN2 and Vitek 2. In addition, isolates were subjected to physiological, biochemical, and morphological characterizations. Furthermore, isolates were identified using 16S rDNA sequence analysis, and multi-locus sequence analysis using atpD, dnaK, efp, and rpoD. To confirm pathogenicity, leaves, fruits, and stems of 3-year-old walnut plants were inoculated with bacterial pathogen suspensions as a foliar spray. One week after inoculation, the gray spots on leaves and yellow halos around the spots were developed. Fruits and stems showed browning symptoms. The pathogen Xaj was re-isolated from all symptomatic tissues to fulfill Koch's postulates, while symptoms were not appeared on control plants. On the other hand, the symptoms were very similar to the symptoms of anthracnose caused by Colletotrichum gloeosporioides. When walnut plants were inoculated with combined pathogens of Xaj and C. gloeosporioides, disease symptoms were greater in comparison with when inoculated alone. Xaj population size was more in the month of April than March due to their dormancy in March, and sensitive to antibiotics such as oxytetracycline and streptomycin, while resistant to copper sulfate.

• Korean Journal of Agricultural Science
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• v.45 no.1
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• pp.19-27
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• 2018

To study the effect of natural anti-microbial chemicals on the growth and quality of chili peppers, chitosan ($100mg/L^{-1}$), stevia ($250mg/L^{-1}$), and the mixture of both chemicals at the same concentration were sprayed after planting at 1-week interval throughout the experimental period. Plant height was measured twice after the $3^{rd}$ and $4^{th}$ applications. Plant height was numerically reduced in all chemical treatments compared to that of untreated control; however, there was no statistical difference between treatments. The fruit quality was examined at commercial maturity, and only minor differences were found in fruit color, length, and dry matter content between the treatments. Although a statistical difference was not present for soluble sugars levels, total phenolics, and capsaicin contents, yield in all chemical treatments significantly increased compared to untreated control. The effect on yield increase was greater at the late harvest season regardless of treatments. Total yield of 4 harvests was higher for the chitosan treatment than other treatments. During the experiment, the entire experimental field was waterlogged for 1 day due to sudden heavy rainfall, which resulted in the occurrence of bacterial browning disease in all treatments. The rate of disease occurrence and the degree of severity, however, were much lower in the chitosan treatment. In conclusion, the potential of chitosan as an alternative antimicrobial agent was confirmed in chili peppers in this study. Further research is required on stevia as an alternative chemical for disease control in chili peppers.

• Korean Journal of Food Science and Technology
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• v.24 no.4
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• pp.341-346
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• 1992

The antimutagenic effects of enzymatic browning reaction products (MEBRPs) of polyphenol compounds (catechol, homocatechol, hydroxyhydroquinone, pyrogallol) by enzyme extracted from mushroom (Agaricus bisporus) were demonstrated through spore rec-assay using B. subtilis $H17(rec^+)$ and $M45(rec^-)$, Ames test using S. typhimurium TA98 and TA100 and SOS chromotest using E. coli PQ37/plasmid pKM101. In spore rec-assay, the MEBRPs showed antimutagenic effects by decreasing of the inhibition zone induced by MNNG. In Ames test with S-9mix in both TA98 and TA100, all of MEBRPs showed strong antimutagenic effects of about 21 to 99% against mutation by $B({\alpha})P$ and Trp-P-1, as adding $300\;{\mu}l$ of the MEBRPs. In SOS chromotest, MEBRPs showed antimutagenic effects by inhibiting the SOS-inducing function induced by 4NQO and MMC, as increasing in concentration of the MEBRPs. But they did not showed mutagenicity in these bacterial assays.

• Journal of Food Hygiene and Safety
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• v.16 no.3
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• pp.232-240
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• 2001

One hundred twenty five bacterial isolates were obtained from the brown blotch-diseased oyster mushrooms collected from markets. Among them, 45 were determined as pathogenic bacteria and white line forming organisms(WLFO) were 6 strains and white line reaction organisms (WLRO) were 6 strains. All of the white line forming isolates were identified as Pseudomonas tolaasii which is a known pathogen of brown blotch disease of oyster mushroom by GC-MIS(Gas chromatography-microbial identification system). Six of the white line reacting organisms were identified as P. chlomraphis, P. fluorescens biotype A and type C. The rest of them were P gingeri, P. agarici, P. fluorescens biotype B, P. chloroyaphis, non-pathogenic P. tolaasii, P. putida biotype A and B etc. For spectrum of activity of tolaasin, culture filtrates from pathogenic isolates were examined by browning of mushroom tissue and pitting of mushroom caps. The weak pathogenic bacteria didn't induce browning or pitting of mushroom tissue. On the other hand, strong pathogenic isolates showed browning and pitting reaction on mushroom. An extracellular toxin produced by P. tolaasii, was investigated. The hemolysis activity test of 6 strains identified as P. tolaasii were 0.8∼0.9 at 600 nm and 3 strains of WLRO were 0.9∼1.0 and Pseudomonas app. were 1.0∼1.2. Observation of fresh mushroom tissue using confocal laser scanning microscopy was carried out for images of optical sectioning and vertical sectioning. Also images of brown blotch diseased oyster mushroom tissue after contamination P. tolaasii was obtained by CLSM.

• Food Science of Animal Resources
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• v.31 no.6
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• pp.907-913
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• 2011

Low-fat and full-fat Mozzarella cheeses were manufactured using ultraflterated-concentrated cow milk with a bacterial cell count of 100, 000 CFU/mL to study the properties of browning, oiling-off, stretchability, and meltability of the cheeses during 3 mon of refrigerated storage. The properties of browning, oiling-off, and stretchability of UF-Mozzarella cheese were affected by fat content, addition of starter and rennet (add 50, 65, and 80% compared with the control, respectively), and baking temperature (280, 300, and $320^{\circ}C$) (p<0.05). The browning and oiling-off scores increased with an increase in baking temperature and lengthen of storage time, but some undesirable results also occurred. The stretchability score improved with an increase in baking temperature, but the gradient decreased with the length of storage time (p<0.05). The meltability score was affected by fat content, concentration factor, and storage period (p<0.05). The result of this study demonstrated the applicability of UF-milk in making Mozzarella cheese with high quality and good palatability.