• Journal of Life Science
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• v.9 no.1
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• pp.84-91
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• 1999

Sediment samples from the waste-oil spilled sites were screened for microorganisms able to degrade the components of crude oil, and 3 strains that could degrade were obtained. The isolated 3 strains (Xl, X2 and X3) metabolized naphthalene and 2-methyl naphthalene about 80$\%$ as well as hexane and hexadecane about 60~70$\%$ as a sole carbon source in 7 days. The degradation of the waste oil was about 60$\%$. The addition of synthetic surfactant, Triton-X 100 or Tween 20 slightly inhibited the growth of the populations. Xl and X2 were gram negative and X3 was gram positive. Xl and X3 showed ampicillin resistancy. Xl strain having 30kb plasmid has been selected for genetic study. The plasmid was isolated and transformed into E. coli. showing the possibility of the genetically engineered degrader.

• The Korean Journal of Food And Nutrition
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• v.9 no.4
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• pp.484-489
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• 1996

The influence of acetic acid (AA) dips on aerobic plate counts (APC), gram-negative bacterial counts (GNC), pH, and sensory tests of pork hams was studied during storage at 4$^{\circ}C$. Pork hams were treated by dipping in 0.5~3.0%(v/v) AA for 0~3 min. Treatments of 1.0~3.0% AA for 3 min completely (P<0.05) inhibited the GNC for 12 days of storage. Treatments of 3.0% AA for 3 min completely (P<0.05) inhibited the APC for 12 days of storage. Treatments with 1.0~3.0% AA for 0~3 min prolonged the microbiological shelf-life to 12 days of storage. Sensory evaluations of pork hams treated with acetic acid were liked less than the fresh controls due to acidic odor and whitness.

• Food Science and Biotechnology
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• v.18 no.3
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• pp.788-792
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• 2009

Gamma $({\gamma})-irradiation$ can be used to control pathogens such as Vibrio vulnificus in seafood. The effects of irradiation on microbial cell populations (%) have been studied in order to develop detection methods for irradiated foods. The method used in this study was ethidium bromide monoazide (EMA) real-time polymerase chain reaction (PCR), using V. vulnificus specific primer, EMA, and $SYBR^{(R)}$ Green to discriminate between ${\gamma}-irradiated$ and non-irradiated cells. Confocal microscope examination showed that ${\gamma}-irradiation$ damaged portions of the cell membrane, allowing EMA to penetrate cells of irradidated V. vulnificus. ${\gamma}-Irradiation$ at 1.08 KGy resulted in log reduction ($-1.15{\pm}0.13$ log reduction) in genomic targets derived from EMA real-time PCR. The combination cold/heat shock resulted in the highest ($-1.74{\pm}0.1$ log reduction) discrimination of dead irradiated V. vulnificus by EMA real-time PCR.

• Food Science and Biotechnology
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• v.17 no.6
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• pp.1337-1340
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• 2008

The objective of this study was to evaluate the microbial safety of raw beef used to produce Korean beef jerky, The raw beef samples harbored large populations of microorganisms. In particular, psychrophilic bacteria were found to be most numerous ($9.2{\times}10^3-1.0{\times}10^5\;CFU/g$) in the samples. Mesophilic bacteria and anaerobic bacteria were present in average numbers ($10^3-10^5\;CFU/g$). Spore-forming bacteria and coliforms were not detected below detection limit. Yeast and molds were detected at $2.2{\times}10^1-7.8{\times}10^2\;CFU/g$ in the raw beef. Ten samples of raw beef were analyzed for the presence of pathogenic bacteria. Bacillus cereus was isolated from sample B, G, and H. The B. cereus isolates from raw beef samples were identified with 99.8% agreement according to the API CHB 50 kit.

• Food Science and Biotechnology
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• v.17 no.4
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• pp.861-864
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• 2008

Enterobacter sakazakii, Salmonella typhimurium. and Bacillus cereus were evaluated on inoculated infant formula by gamma irradiation treatment as a method to provide microbial safety. The infant formula inoculated with the major pathogenic bacteria was treated at irradiation dose of 0, 3, 5, and 10 kGy, respectively. After treatment, the samples were individually packaged and stored at $20^{\circ}C$. Microbiological data during storage represented that the populations of E. sakazakii, S. typhimurium, and B. cereus were reduced with the increase of irradiation dose by 4 to 5 log reductions. In particular, E. sakazakii, S. typhimurium. and B. cereus were eliminated at 10, 5, and 3 kGy, respectively. E. sakazakii was the most radiation-resistant, while B. cereus was the least. Our results represent that gamma irradiation below 10 kGy should eliminate the growth of the major pathogenic bacteria in infant formula during storage.

• Environmental Engineering Research
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• v.23 no.4
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• pp.420-429
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• 2018

Soil stabilization is a soil remediation technique that reduces the mobility of heavy metals in soils. Although it is a well-established technique, it is nonetheless essential to perform a follow-up chemical assessment via a leaching test to evaluate the immobilization of heavy metals in the soil matrix. Unfortunately, a standard chemical assessment is not sufficient for evaluation of the biological functional state of stabilized soils slated for agricultural use. Therefore, it is useful to employ a pyrosequencing-based microbial community analysis for the purpose. In this study, a recently stabilized site in the proximity of an exhausted mine was analyzed for bacterial diversity, richness, and relative abundance as well as the effect of environmental factors. Based on the Shannon and Chao1 indices and rarefaction curves, the results showed that the stabilized layer exhibited lower bacterial diversity than control soils. The prevalence of dominant bacterial populations was examined in a hierarchical manner. Relatively high abundances of Proteobacteria and Methylobacter tundripaludum were observed in the stabilized soil. In particular, there was substantial abundance of the Methylobacter genus, which is known for its association with heavy metal contamination. The study demonstrated the efficacy of (micro)biological assessment for aiding in the understanding and post-management of stabilized soils.

• Microbiology and Biotechnology Letters
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• v.47 no.2
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• pp.303-309
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• 2019

Earlier studies by our group revealed that gallic acid in phytochemicals stimulated biofilm production in epiphytes, while caffeic acid in phytochemicals inhibited biofilm production in non-epiphytes. It is well documented that antimicrobial secretion by some epiphytic bacteria inhibits non-epiphytic bacterial growth on leaf surfaces. These selection criteria help plants choose their microbial inhabitants. Calcium and iron in phytochemicals also stimulate biofilm formation and thus, may be selection criteria adopted by plants with respect to their native epiphytic population. Furthermore, the processing of leaves during phytochemical extraction impacts the composition of the extract, and therefore its ability to affect bacterial biofilm formation. Computation of the Hurst exponent using biofilm thickness data obtained from the Ellipsometry of Brewster Angle Microscopic (BAM) images is an efficient tool for understanding the impact of phytochemicals on epiphytic and non-epiphytic populations when compared to fluorescent microscopy, scanning electron microscopy, and staining techniques. To the best of our knowledge, this is the first report that uses the Hurst exponent to elucidate the mechanism involved in plant microbe interaction.

• Journal of Microbiology and Biotechnology
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• v.32 no.7
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• pp.862-868
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• 2022

Microalgae are photosynthetic cyanobacteria and eukaryotic microorganisms, mainly living in the water. In agriculture, numerous studies have been conducted to utilize microalgae as a biostimulant resource. Scenedesmus has been known to be one such microalga that can promote plant growth by secretion of auxin or cytokinin hormone analogs. However, no research has been performed on the effect of microalgae treatment on plant microbiota communities. This study was conducted to investigate the mode of action of microalgae as biostimulants in a plant microbiota perspective by using Scenedesmus sp. CHK0059 (also known as species Chlorella fusca), which has been well documented as a biostimulant for strawberries. The strawberry cultivar Keumsil was bred with Seolhyang and Maehyang as the parent cultivars. Using these three cultivars, microbiota communities were evaluated for changes in structural composition according to the CHK0059 treatment. CHK0059-treated Seolhyang, and CHK0059-untreated Maehyang were similar in microbial diversity in the endosphere. From a microbiota community perspective, the diversity change showed that CHK0059 was affected by the characteristics of the host. Conversely, when CHK0059 treatment was applied, populations of Streptomyces and Actinospica were observed in the crown endosphere.

• Journal of Microbiology
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• v.42 no.4
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• pp.285-291
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• 2004

The soil bacterial community and some inoculated bacteria were monitored to assess the microbial responses to prescribed fire in their microcosm. An acridine orange direct count of the bacteria in the unburned control soil were maintained at a relatively stable level $(2.0\~2.7\times10^9\;cells/g^{-1}{\cdot}soil)$ during the 180 day study period. The number of bacteria in the surface soil was decreased by fire, but was restored after 3 months. Inoculation of some bacteria increased the number of inoculated bacteria sev­eral times and these elevated levels lasted several months. The ratios of eubacteria detected by a flu­orescent in situ hybridization (FISH) method to direct bacterial count were in the range of $60\~80\%$ during the study period, with the exception of some lower values at the beginning, but there were no definite differences between the burned and unburned soils or the inoculated and uninoculated soils. In the unburned control soil, the ratios of $\alpha-,\beta-\;and\;\gamma-subgroups$ of the proteobacteria, Cytophaga-Fla­vobacterium and other eubacteria groups to that of the entire eubacteria were 13.7, 31.7, 17.1, 16.8 and $20.8\%,$ respectively, at time 0. The overall change on the patterns of the ratios of the 5 subgroups of eubacteria in the uninoculated burned and inoculated soils were similar to those of the unburned con­trol soil, with the exception of some minor variations during the initial period. The proportions of each group of eubacteria became similar in the different microcosms after 6 months, which may indicate the recovery of the original soil microbial community structure after fire or the inoculation of some bac­teria. The populations of Azotobacter vinelandii, Bacillus megaterium and Pseudomonas fluorescens, which had been inoculated to enhance the microbial activities, and monitored by FISH method, showed similar changes in the microcosms, and maintained high levels for several months.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.2
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• pp.239-246
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• 2015

The present study was conducted to evaluate the effect of the dietary supplementation of Bacillus amyloliquefaciens-based direct-fed microbial (DFM) on growth performance, nutrient utilization, intestinal morphology and cecal microflora in broiler chickens. A total of two hundred and eighty eight 1-d-old Arbor Acres male broilers were randomly allocated to one of four experimental treatments in a completely randomized design. Each treatment was fed to eight replicate cages, with nine birds per cage. Dietary treatments were composed of an antibiotic-free basal diet (control), and the basal diet supplemented with either 15 mg/kg of virginiamycin as antibiotic growth promoter (AGP), 30 mg/kg of Bacillus amyloliquefaciens-based DFM (DFM 30) or 60 mg/kg of Bacillus amyloliquefaciens-based DFM (DFM 60). Experimental diets were fed in two phases: starter (d 1 to 21) and finisher (d 22 to 42). Growth performance, nutrient utilization, morphological parameters of the small intestine and cecal microbial populations were measured at the end of the starter (d 21) and finisher (d 42) phases. During the starter phase, DFM and virginiamycin supplementation improved the feed conversion ratio (FCR; p<0.01) compared with the control group. For the finisher phase and the overall experiment (d 1 to 42) broilers fed diets with the DFM had better body weight gain (BWG) and FCR than that of control (p<0.05). Supplementation of virginiamycin and DFM significantly increased the total tract apparent digestibility of crude protein (CP), dry matter (DM) and gross energy during both starter and finisher phases (p<0.05) compared with the control group. On d 21, villus height, crypt depth and villus height to crypt depth ratio of duodenum, jejunum, and ileum were significantly increased for the birds fed with the DFM diets as compared with the control group (p<0.05). The DFM 30, DFM 60, and AGP groups decreased the Escherichia coli population in cecum at d 21 and d 42 compared with control group (p<0.01). In addition, the population of Lactobacillus was increased in DFM 30 and DFM 60 groups as compared with control and AGP groups (p<0.01). It can be concluded that Bacillus amyloliquefaciens-based DFM could be an alternative to the use of AGPs in broilers diets based on plant protein.