• Membrane and Water Treatment
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• 제6권3호
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• pp.189-203
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• 2015

Membrane biofouling impedes wide application of membrane bioreactor (MBR) for wastewater treatment. Recently, quorum sensing (QS) mechanisms are accounted for one of major mechanisms in biofouling of MBRs. In this study, vanillin was applied to investigate reduction of biofouling in MBRs. MBR sludge was analyzed to contain QS signal molecules by cross-feeding biosensor assay and HPLC. In addition, the inhibitory activity of vanillin against bacterial quorum sensing was verified using an indicator strain CV026. The vanillin doses greater than 125 mg/L to 100 mL of MBR sludge showed 25% reduction of biofilm formed on the membrane surfaces. Two MBRs, i.e., a typical MBR as a control and an MBR with vanillin, were operated. The TMP increases of the control MBR were more rapid compared to those of the MBR with the vanillin dose of 250 mg/L. The treatment efficiencies of the two MBRs on organic removal and MLSS were maintained relatively constant. Extracellular polymeric substance concentrations measured at the end of the MBR operation were 173 mg/g biocake for the control MBR and 119 mg/g biocake for the MBR with vanillin. Vanillin shows great potential as an anti-biofouling agent for MBRs without any interference on microbial activity for wastewater treatment.

• Journal of Microbiology and Biotechnology
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• 제17권5호
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• pp.769-773
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• 2007

With the aim to produce ascorbic acid-2-phosphate(AsA-2-P) from L-ascorbic acid(AsA, Vitamin C), nine bacteria conferring the ability to transform AsA to AsA-2-P were isolated from soil samples alongside known strains from culture collections. Most isolates were classified to the genus Brevundimonas by 16S phylogenetic analysis. Among them, Brevundimonas diminuta KACC 10306 was selected as the experimental strain because of its the highest productivity of AsA-2-P. The optimum set of conditions for the AsA-2-P production from AsA using resting cells as the source of the enzyme was also investigated. The optimum cultivation time was 16 h and the cell concentration was 120g/l(wet weight). The optimum concentrations of AsA and pyrophosphate were 550mM and 450mM, respectively. The most effective buffer was 50mM sodium formate. The optimum pH was 4.5 and temperature was $40^{\circ}C$. Under the above conditions, 27.5g/l of AsA-2-P was produced from AsA after 36 h of incubation, which corresponded to a 19.7% conversion efficiency based on the initial concentration of AsA.

• Journal of Microbiology
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• 제41권4호
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• pp.271-276
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• 2003

The inoculation of some microorganisms into a microcosm containing soil from a barren lakeside area at Lake Paro in Kangwon-do enhanced plant growth significantly. The direct and viable counts of soil bacteria and soil microbial activities measured by electron transport system assay and fluorescein diacetate hydrolysis assay were higher in inoculated soil. The plant growth promoting effect of this inoculation may be caused by phytohormone production and the solubilization of insoluble phosphates by the inoculated bacteria. Three inoculated strains of Pseudomonas fluorescens produced several plant growth promoting phytohormones, including indole-3-acetic acid (auxin), which was confirmed by thin layer chromatography and GC/MS. P. fluorescens strain B16 and M45 produced 502.4 and 206.1 mg/l of soluble phosphate from Ca3(PO4)2 and hydroxyapatite, respectively. Bacillus megaterium showed similar solubilization rates of insoluble phosphates to those of Pseudomonas spp. We believe that this plant growth promoting capability may be used for the rapid revegetation of barren or disturbed land.

• Food Science and Biotechnology
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• 제15권3호
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• pp.458-461
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• 2006

To determine whether the toxicity of Bacillus cereus would be seen in human cell lines and mice, we screened B. cereus B-38B, B. cereus B-50B, and B. cereus KCCM40935 for genes that coded for 5 enterotoxins using the polymerase chain reaction and cultivated them for 17 hr, by whose time they had grown to $10^7-10^8$ colony-forming units (CFU) per milliliter. Cell-free supernatant was added to make up 1% of the total reaction solution. Human cells from normal lung, lung carcinoma, embryonic kidney, and cervical adenocarcinoma cell lines were grown in culture. The cytotoxicity induced by adding the reaction solution was indicated by cell death rates of 0 to 70%, depending on the bacterial strain involved and the cell line. A lethality of 20% was observed when B. cereus cultures containing $10^7-10^8$ viable cells were administrated orally to mice. Therefore, the culture of B. cereus containing $10^7-10^8$ viable cells seems to have high cytotoxicity on human cell lines and lethality on mice.

• 한국식품영양과학회지
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• 제26권6호
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• pp.1077-1085
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• 1997

This study was carried out to elucidate the utilization of the fusant for shortening the ripening time by making an observation of the microstructure and the profile of component change. In ripening cheese, moisture content of the sample treated with tested strain is not a remarkable difference among the test samples. With an increase of the ripening time, L. helveticus showed the highest increase in protein content, followed by fusant, and then L. bulgaricus. The fat content of all starters was gradually decreased while it was it was rapidly decreased after 7 days. The pH of all starters was gradually decreased when the ripening time increased. The titratable acidity was greatly increased between a 9th day and a 15th day ripening. In investigating the light microscopic microstructure of ripened cheese samples, the sample treated with fusant indicated little difference from the other starters in decomposition of protein and fat components by microbial enzymes. In SEM observation, the structure of all cheese samples was uniform and the rough texture was converted into smooth texture by the interaction of cheese components and the abscission of single bond in casein matrix when the ripening time is increased. The fusant showed similar results in the examination of component change and its microstructure compared with the other starters. Therefore, it was revealed that the fusant can be partially used as a cheese starter instead of conventional starters by replacing them or combining them together with the other starters for shortening the ripening time.

• 한국토양비료학회지
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• 제48권1호
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• pp.36-43
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• 2015

Excess use of chemical fertilizer causes soil acidification and accumulation of salt, and thus might bring to desertification of soil. To overcome this problem, it needs limited usage of chemical fertilizer and increased usage of natural fertilizer as an alternative. In this study, dry soil-borne Bacillus sp. SHL-3, which was isolated from arid and barren soil, with plant growth promoting activity was isolated for identification and to determine optimal culture condition. A bacterial strain SHL-3 had the IAA productivity ($5.16{\pm}0.10mg\;L^{-1}$), ACC deaminase activity ($0.36{\pm}0.09$ at 51 hours) and siderophore synthesis. It was identified as genus Bacillus sp.. Also, optimal culture condition of SHL-3 were $20^{\circ}C$ and pH 7 in LB medium. Bacillus sp. SHL-3 had up to 4% salt tolerance in the medium. We evaluated the plant growth promotion ability of SHL-3 using yam (Dioscorea japonica Thunb.). As a result, Bacillus sp. SHL-3 was effective on the increase of the shoot length (202.4% increase for 91 days). These results indicate that Bacillus sp. SHL-3 can serve as a promising microbial resource for the biofertilizers of soil.

• Journal of Microbiology and Biotechnology
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• 제29권6호
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• pp.887-896
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• 2019

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based pathogen identification relies on the ribosomal protein spectra provided in the proprietary database. Although these mass spectra can discern various pathogens at species level, the spectra-based method still has limitations in identifying closely-related microbial species. In this study, to overcome the limits of the current MALDI-TOF MS identification method using ribosomal protein spectra, we applied MALDI-TOF MS of low-mass profiling to the identification of two genetically related Bacillus species, the food-borne pathogen Bacillus cereus, and the insect pathogen Bacillus thuringiensis. The mass spectra of small molecules from 17 type strains of two bacilli were compared to the morphological, biochemical, and genetic identification methods of pathogens. The specific mass peaks in the low-mass range (m/z 500-3,000) successfully identified various closely-related strains belonging to these two reference species. The intensity profiles of the MALDI-TOF mass spectra clearly revealed the differences between the two genetically-related species at strain level. We suggest that small molecules with low molecular weight, 714.2 and 906.5 m/z can be potential mass biomarkers used for reliable identification of B. cereus and B. thuringiensis.

• Journal of Microbiology and Biotechnology
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• 제29권4호
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• pp.507-517
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• 2019

Rhodotorula is a group of pigment-producing yeasts well known for its intracellular biosynthesis of carotenoids such as ${\beta}-carotene$, ${\gamma}-carotene$, torulene and torularhodin. The great potential of carotenoids in applications in food and feed as well as in health products and cosmetics has generated a market value expected to reach over $2.0 billion by 2022. Due to growing public concern over food safety, the demand for natural carotenoids is rising, and this trend significantly encourages the use of microbial fermentation for natural carotenoid production. This review covers the biological properties of carotenoids and the most recent findings on the carotenoid biosynthetic pathway, as well as strategies for the metabolic engineering methods for the enhancement of carotenoid production by Rhodotorula. The practical approaches to improving carotenoid yields, which have been facilitated by advancements in strain work as well as the optimization of media and fermentation conditions, were summarized respectively.

• Journal of Microbiology and Biotechnology
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• 제29권5호
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• pp.667-686
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• 2019

Streptomyces are attractive microbial cell factories that have industrial capability to produce a wide array of bioactive secondary metabolites. However, the genetic potential of the Streptomyces species has not been fully utilized because most of their secondary metabolite biosynthetic gene clusters (SM-BGCs) are silent under laboratory culture conditions. In an effort to activate SM-BGCs encoded in Streptomyces genomes, synthetic biology has emerged as a robust strategy to understand, design, and engineer the biosynthetic capability of Streptomyces secondary metabolites. In this regard, diverse synthetic biology tools have been developed for Streptomyces species with technical advances in DNA synthesis, sequencing, and editing. Here, we review recent progress in the development of synthetic biology tools for the production of novel secondary metabolites in Streptomyces, including genomic elements and genome engineering tools for Streptomyces, the heterologous gene expression strategy of designed biosynthetic gene clusters in the Streptomyces chassis strain, and future directions to expand diversity of novel secondary metabolites.

• International Journal of Clinical Preventive Dentistry
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• 제14권4호
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• pp.216-221
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• 2018

Objective: In this study, we tried to investigate the antimicrobial activity of natural herbaceous plant-derived essential oils against oral disease-causing bacterial strains and establish the scientific evidences to apply them to the dentifrice, mouthwash, and other uses. Methods: We used the disk diffusion method with 23 types of 100% natural essential oils to verify the antimicrobial effect against Streptococcus mutans, Porphyromonas gingivalis, and Lactobacillus rhamnosus. After adhering to the surface of the plate culture medium, $20{\mu}l$ of the essential oil was prepared, and the diameter of the transparent ring was measured after incubation for 24 hours. All the experiments were repeated three times. Results: Among 23 types of oils, 13 were effective against all three strains: myrrh, ginger, basil, carrot seed, tea tree, patchouli, ylang ylang, cypress, lemongrass, cinnamon, peppermint, lavender, and eucalryptus. Seventeen oils were effective against S. mutans, and myrrh, basil, and carrot seed showed high antimicrobial activity. Eighteen oils were effective against P. gingivalis, and tea tree, carrot seed, and cinnamons showed high antimicrobial activity. Sixteen oils were effective against L. rhamnosus, and carrot seed and peppermint cinnamon showed high antimicrobial activity. Conclusion: Consequently, 13 essential oils showed the antimicrobial activity against three bacterial strains, which indicates these essential oils might be used as the effective materials to suppress the growth of oral-disease inducing microorganisms. Moreover, essential oils that have been analyzed activities in this study will be mixed up within the constant range and analyzed their antimicrobial effects to examine the synergistic activity among them.