• Journal of Microbiology and Biotechnology
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• v.16 no.2
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• pp.240-246
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• 2006

Cyanobacteria are present abundantly in rice fields and are important in helping to maintain rice fields fertility through nitrogen fixation. Many rice fields soil contain a high density of cyanobactera, and over 50% of cyanobacterial genera that are in existence in rice paddy fields are heterocystous filamentous forms. A total of 142 isolates of heterocystous filamentous cyanobacteria were screened from 100 soil samples taken from rice paddy fields in 10 different locations across Korea, classified according to their morphological characteristics under light microscopy, and their susceptibly to fungicides examined. The collected blue-green alga were classified into a total of 14 genera, including seven genera of filamentous cyanobacteria and seven genera of nonfilamentous cyanobacteria. In particular, 142 heterocystous filamentous cyanobacteria were isolated and classified into six genera, including Anabaena, Nostoc, Calothrix, Cylindrospermum, Nodularia, Scytomena, and Tolypotrix. Yet, over 90% of the heterocystous filamentous cyanobacteria isolated from the rice paddy fields belonged to two genera: Anabaena and Nostoc. The response of 129 $N_2-fixing$ cyanobacterial isolates, 53 Anabaena and 76 Nostoc, to 10 fungicides was then investigated. The results showed that the Nostoc spp. were more tolerant of the ten tested fungicides than the Anabaena spp., and among the ten tested fungicides, benomyl showed the highest acute toxicity to Anabaena spp. and Nostoc spp. In conclusion, although benomyl is a very useful agent to control phytopathogenic fungi, the application of this fungicide to rice fields should be considered because of its toxicity to the heterocystous filamentous cyanobacteria.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.4
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• pp.593-601
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• 2012

Heavy metals and metalloids removal can be considered as one of the most important world challenges because of their toxicity and direct impact on human health. Many processes have been introduced but biological processes of remediation seem to offer the most suitable solution in terms of efficiency and low cost. Actinobacteria constitute one of the major microbial populations in soil, and this can be attributed to their adaptive morphological structure as well as their exceptional metabolic power. Among microbes, actinobacteria are morphologic intermediate between fungi and bacteria. Studies on microbial diversities in metal contaminated lands have shown that actinobacteria may constitute a dominantly active microbiota in addition to ${\alpha}$ Proteobacteria. Furthermore, isolation studies have shown metal removal mechanisms which are reminiscent of notable multiresistant strains, such as Cupriavidus metallidurans. Apart from members of genus Streptomyces, which produce more than 90% of commercialized antibiotics, and the nitrogen fixing Frankia, little attention has been given to other members of this phylum. This is because of difficult culture condition requirements and maintenance. In this review, we focused on specific isolation of actinobacteria and their potential applications in metal bioremediation and plant growth promotion.

• Journal of Microbiology and Biotechnology
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• v.16 no.7
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• pp.1041-1046
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• 2006

Selenium-containing peptide (selenium peptide) was produced by autolysis of total proteins of Saccharomyces cerevisiae grown with inorganic selenium. Selenium peptide exhibited antioxidant activity as a glutathione peroxidase (GPx) mimic, and its activity was dependent on the hydrolysis methods. The GPx-like activity of the hydrolyzed selenium peptide increased 2.7-folds when digested by protease, but decreased by acid hydrolysis. During the autolysis of the yeast cell, the GPx-like activity and selenium content increased 4.3- and 2.3-folds, respectively, whereas the average molecular weight (MW) of selenium peptide decreased 70%. The GPx-like activity was dependent on the MW of selenium peptide and was the highest (220 U/mg protein) at 9,500 dalton. The maximum GPx-like activity (28,600 U/g cell) was obtained by 48 h of autolysis of the cells, which were precultured with 20 ppm of selenate. Selenium peptide showed little toxicity, compared with highly toxic inorganic selenium. These results show the potential of selenium peptide as a nontoxic antioxidant that can be produced by simple autolysis of yeast cells.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.1114-1119
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• 2012

This study was conducted to assess the microbial toxicity of ionic silver solution ($Ag^+N$) and silver nanoparticle suspension ($Ag^0NP$) based on the Microtox bioassay. In this test, the light inhibition of luminescent bacteria was measured after 15 and 30 min exposure to aqueous solutions and soils spiked with a dilution series of $Ag^+N$ and $Ag^0NP$. The resulting dose-response curves were used to derive effective concentration (EC25, $EC_{50}$, EC75) and effective dose ($ED_{25}$, $ED_{50}$, $ED_{75}$) that caused a 25, 50 and 75% inhibition of luminescence. In aqueous solutions, $EC_{50}$ value of $Ag^+N$ after 15 min exposure was determined to be < $2mg\;L^{-1}$ and remarkably lower than $EC_{50}$ value of $Ag^0NP$ with $251mg\;L^{-1}$. This revealed that $Ag^+N$ was more toxic to luminescent bacteria than $Ag^0NP$. In soil extracts, however, $ED_{50}$ value of $Ag^+N$ with 196 mg kg-1 was higher than $ED_{50}$ value of $Ag^0NP$ with $104mg\;kg^{-1}$, indicating less toxicity of $Ag^+N$ in soils. The reduced toxicity of $Ag^+N$ in soils can be attributed to a partial adsorption of ionic $Ag^+$ on soil colloids and humic acid as well as a partial formation of insoluble AgCl with NaCl of Microtox diluent. This resulted in lower concentration of active Ag in soil extracts obtained after 1 hour shaking with $Ag^+N$ than that spiked with $Ag^0NP$. With longer exposure time, EC and ED values of both $Ag^+N$ and $Ag^0NP$ decreased, so their toxicity increased. The toxic characteristics of silver nanomaterials were different depending on existing form of Ag ($Ag^+$, $Ag^0$), reaction medium (aqueous solution, soil), and exposure time.

• Journal of Applied Biological Chemistry
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• v.61 no.2
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• pp.151-155
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• 2018

In this study, cinnamon essential oil (CEO) was formulated as emulsifiable concentrate (EC) and a granule. For the evaluation of their negative effects on the ecosystem, acute toxicities against Cyprinus carpio was determined in a static condition. The formulations were made using CEOs extracted by 3 different methods (steam distillation (SD), solvent extraction and supercritical fluid extraction (SFE)) and were tested to obtain $LC_{50}$ values. Among the ECs, EC including CEO extracted by SFE showed highest acute toxicity against C. carpio. Among the granules, a granule including CEO extracted by SD showed highest acute toxicity against C. carpio. Nevertheless, $LC_{50}$ of EC and a granule formulation with CEOs was higher than toxicity level III of pesticide standardized by Korea rural development administration. These results were similar to those using zebrafishes. Chronic toxicities were not found for 45 days in zebrafishes until $500{\mu}gL^{-1}$ level of EC formulation including CEO obtained by the SD. Based on these results, EC formulation of CEOs may be considered to be used as environmental-friendly natural insecticides in accordance with the standards.

• Environmental Analysis Health and Toxicology
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• v.29
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• pp.8.1-8.8
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• 2014

Objectives An ecofriendly alternative to chemical pesticides is bio-pesticides, which are derived from natural sources. The interest in bio-pesticides is based on the disadvantages associated with chemical pesticides. Methods We conducted acute toxicity assessments of camphor, a major component of bio-pesticides, by using Daphnia magna (D. magna) as well as assessed the morphological abnormalities that occurred in Danio rerio (D. rerio) embryos. Results The median effective concentration of camphor on D. magna after 48 hours was $395.0{\mu}M$, and the median lethal concentration on D. rerio embryos after 96 hours was $838.6{\mu}M$. The no observed effect concentration and predicted no effect concentration of camphor on D. magna, which was more sensitive than D. rerio, were calculated as $55.2{\mu}M$ and $3.95{\mu}M$, respectively. Morphological abnormalities in D. rerio embryos exposed to camphor increased over time. Coagulation, delayed hatching, yolk sac edema, pericardial edema, and pigmentation of embryos mainly appeared between 24 and 48 hours. Further, symptoms of scoliosis and head edema occurred after 72 hours. In addition, bent tails, ocular defects and collapsed symptoms of fertilized embryonic tissue were observed after 96 hours. Conclusions The camphor toxicity results suggest that continuous observations on the ecosystem are necessary to monitor toxicity in areas where biological pesticides containing camphor are sprayed.

• The Journal of Korean Medicine
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• v.33 no.3
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• pp.200-230
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• 2012

Objectives: Ginseng, Panax ginseng C. A., white ginseng, has been used for thousands of years in Traditional Korean Medicine. Red ginseng can be made by a steaming process of white ginseng changing a variety of ginsenosides and ingredients such as dencichine. This article reviews red ginseng for mechanisms for pharmacodynamics and toxicity based on the content of ginseng's active ingredients, ginsenoside changed by steaming. Methods: The following electronic databases were searched: PubMed, Science Direct and Chinese Scientific Journals full text database (CQVIP), and KSI (Korean Studies Information) from their respective inceptions to June 2012. Results: Compared with unsteamed ginseng, the content of ginsenosides Rg2, Rg3, Rg5, Rh1, Rh2 and Rk1 called red ginseng-specific ginsenosides increased after the steaming process. Different ginsenosides have shown a wide variety of effects such as lowering or raising blood sugar and blood pressure or stimulating or sedating the nervous system. Especially, the levels of Rg2, Rg3, Rg5, Rh1, Rh2 and Rk1 were increased by the steaming process, showing a variety of pharmacodynamics in biological systems. Also, various processing methods such as puffing and fermentation have been developed in processing crude ginseng or red ginseng, affecting the content of ginseng's ingredients. The safety issue could be the most critical, specifically, on changed ginseng's ingredients such as dencichine. The level of dencichine was significantly reduced in red ginseng by the steaming process. In addition, the possible toxicity for red ginseng was affected by cytochrome P450, a herbal-drug interaction. Conclusions: The variety of pharmacological and toxicological properties should be changed by steaming process of Panax ginseng C. A., white ginseng. Even if it is not sure whether the steaming process of white ginseng would be better pharmacologically, it is sure that steaming reduces the level of dencichine causing a lower toxicity to the nervous system.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3301-3306
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• 2013

This paper aims to address the cellular toxicity of ultra-pure titanium dioxide ($TiO_2$) and zinc oxide (ZnO) nanoparticles (NPs) frequently employed in sunscreens as inorganic physical sun blockers to provide protection against adverse effects of ultraviolet (UV) radiation including UVB (290-320 nm) and UVA (320-400 nm). In consideration that the production and the use of inorganic NPs have aroused many concerns and controversies regarding their safety and toxicity and that microsized $TiO_2$ and ZnO have been increasingly replaced by $TiO_2$ and ZnO NPs (< 100 nm), it is very important to directly investigate a main problem related to the intrinsic/inherent toxicity of these NPs and/or their incompatibility with biological objects. In the present study, we took advantage of the laser-assisted method called laser ablation for generation of $TiO_2$ and ZnO NPs. NPs were prepared through a physical process of irradiating solid targets in liquid phase, enabling verification of the toxicity of ultra-pure NPs with nascent surfaces free from any contamination. Our results show that $TiO_2$ NPs are essentially non-poisonous and ZnO NPs are more toxic than $TiO_2$ NPs based on the cell viability assays.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1555-1560
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• 2010

Quantum dots (QDs) are extensively employed for biomedical research as a fluorescence reporter and their use for various labeling applications will continue to increase as they are preferred over conventional labeling methods for various reasons. However, concerns have been raised over the toxicity of these particles in the biological system. Till date no thorough investigation has been carried out to identify the molecular signatures of QD mediated toxicity. In this study we evaluated the toxicity of CdSe, $Cd_{1-x}Zn_xS$/ZnS and CdSe/ZnS quantum dots having different spectral properties (red, blue, green) using human embryonic kidney fibroblast cells (HEK293). Cell viability assay for both short and long duration exposure show concentration material dependent toxicity, in the order of CdSe > $Cd_{1-x}Zn_xS$/ZnS > CdSe/ZnS. Genome wide changes in the expression of genes upon QD exposure was also analyzed by wholegenome microarray. All the three QDs show increase in the expression of genes related to apoptosis, inflammation and response towards stress and wounding. Further comparison of coated versus uncoated CdSe QD-mediated cell death and molecular changes suggests that ZnS coating could reduce QD mediated cytotoxicity to some extent only.

• KSBB Journal
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• v.14 no.6
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• pp.747-753
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• 1999

Microbial surfactants are more effective and environmentally friendly than many synthetic surfactants. Sophorolipid, a glycolipid type microbial surfactant, is produced from C. bombiocola. Cultivation techniques to increase the productivity have been developed using various carbon sources and reactor setup, reaching its concentration upto 100-300 g/L. Due to its high productivity and non-toxicity, sophorolipid became one of the most promising alternative to synthetic surfactants. Fermentative production of sophorolipid depends primarily on the carbon sources, such as glucose and vegetable oils, and nitrogen sources. Chemical modification of the sophorolipid produces various derivative with different physical properties including hydrophile-liphophilie balance(HLB), emulsion formation, surface tension and dispersing ability. Commercial potentials of sophorolipid in the cosmetic, health care and environment clean-up industries have been discussed.