• Journal of Microbiology and Biotechnology
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• v.20 no.5
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• pp.917-924
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• 2010

The practicability of transgenic tobacco engineered to express bacterial native mercuric reductase (MerA), responsible for the transport of $Hg^{2+}$ ions into the cell and their reduction to elemental mercury ($Hg^0$), without any codon modification, for phytoremediation of mercury pollution was evaluated. Transgenic tobacco plants reduce mercury ions to the metallic form; take up metallic mercury through their roots; and evolve the less toxic elemental mercury. Transformed tobacco produced a large amount of merA protein in leaves and showed a relatively higher resistance phenotype to $HgCl_2$ than wild type. Results suggest that the integrated merA gene, encoding mercuric reductase, a key enzyme of the bacterial mer operon, was stably integrated into the tobacco genome and translated to active MerA, which catalyzes the bioconversion of toxic $Hg^{2+}$ to the least toxic elemental $Hg^0$, and suggest that MerA is capable of reducing the $Hg^{2+}$, probably via NADPH as an electron donor. The transgenic tobacco expressing merA volatilized significantly more mercury than wild-type plants. This is first time we are reporting the expression of a bacterial native merA gene via the nuclear genome of Nicotiana tabacum, and enhanced mercury volatilization from tobacco transgenics. The study clearly indicates that transgenic tobacco plants are reasonable candidates for the remediation of mercurycontaminated areas.

• Mycobiology
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• v.32 no.2
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• pp.74-78
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• 2004

An alkaline protease produced by Aspergillus niger C-15 was purified and characterized. The enzyme was purified 19.41-fold with a specific activity of 74150 U/mg and a recovery of 34.4% by gel filtration and ion exchange chromatography. The molecular weight of the enzyme was estimated to be 34 kDa. The optimum pH and temperature for the protease activity were pH 8.0 and $60^{\circ}C$, respectively. The enzyme activity inhibited by EDTA suggests that the preparation contains a metalloprotease. The enzyme activity of the metalloprotease was completely inhibited by 5 mM $HgCl_2$ and $FeCl_3$, while partially inhibited by $CuSO_4$, and $MnCl_2$. When polyols such as glycerol, mannitol, sorbitol and xylitol, were added to the reaction medium, most polyols tested enhanced protease activity. Especially, glycerol showed the highest effect. The alkaline metalloprotease was stable at high temperature and retained more than 90% of the initial activity at $60^{\circ}C$ and 86.4% under addition of glycerol.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.2
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• pp.240-245
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• 1993

The optimum pH and temperature for the purified extracellular enzyme activity were 8.0 and 37$^{\circ}C$, respectively. NaCl was required for the activation of the enzyme and optimum concentration was 0.5M. This enzyme activity was inhibited by HgC $l_2$, CoC $l_2$ and ZnC $l_2$ and stimulated by CaC $l_2$. The activity of enzyme was increased by L-cysteine and 2-mercaptoethanol, but decreased by ο-phenanthroline, $\rho$-CMB, EDTA and iodoacetate. The $K_{m}$ and $V_{max}$ values of extracellular enzyme appeared as 0.717% and 15.39U/mg, respectively.y.

• Applied Biological Chemistry
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• v.33 no.4
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• pp.337-342
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• 1990

The pretense from Halobacterium sp. was purified by ethanol precipitation and gel filtration on Sephadex G-75 and G-100. The purified enzyme was found to be homogeneous by polyacrylamide gel electrophoresis It's specific activity was 364units/mg protein and yield was 14% of the total activity of the culture filtrate. The Km value against casein was determined to be $4.2{\times}10^{-4}M$ by Lineweaver-Burk plot The optimal temperature and pH for the enzyme activity were $35^{\circ}C$ and pH 8.0, respectively. The enzyme was stable from 5.0 to 11.0 at relatively wide range of pH but was inactivated at the temperature above $50^{\circ}C$. $Ca^{2+}$ and $Mg^{2+}$ appeared to react as activators whereas $Fe^{3+},\;Zn^{2+},\;Cu^{2+},\;Hg^{2+}\;and\;Cd^{2+}$ as inhibitors. The enzyme activity reduced with increasing the concentration of NaCl : the apparent activity with 2M NaCl was 65% as compared with that without the salt However the enzyme was unstable without salts : the activity was lost when dialyzed against distilled water for 2hr, whereas maintained against 0.1M solution of $CaCl_2$ for 6hr.

• Microbiology and Biotechnology Letters
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• v.14 no.4
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• pp.271-277
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• 1986

A sisomicin-producing strain, Micromonospora inyoensis, was treated with various mutagens. The optimal death rates to obtain the high-producers of sisomicin were 90% for ultraviolet light, 99% for nitrosoguanidine, and 99.3% for nitrous acid, respectively. In place of the method of liquid culture, an agar plug method, which is easy and convenient, was used to measure the antibiotic-producing abilities of the strains isolated from mutagen-treated cells. On the other hand, as the selection method of overproducing mutants after mutagenesis, gradient agar plates which included various antibiotics and salts were used. Among the antibiotics and salts tested, gentamicin and kanamycin as antibiotics, and CuCl$_2$ and HgCl$_2$ as salts, were effective to select the high-producers of sisomicin.

• Microbiology and Biotechnology Letters
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• v.27 no.2
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• pp.129-135
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• 1999

EH-1 was highest at 9 days of incubation. This regrowth and enzymatic activity of Haloarcular sp. EH-1 was highest at 9 days of incubation. This amylase was purified by acetone fractionation, DEAG-Cellulose column chromatography, 1st Sephadex G-75 gel filtration, CM-Cellulose column chromatography and 2nd Sephadex G-75 gel filtration. The amylase was purified about 98.64 fold with a yield of 11.75%. The molecular weight of amylase was estimated to be about 43,000and 40,000 by gel filtration and SDS-polyacrylamide gel electrophoresis, respectively, suggesting that the enzyme was a monomer. Amylase had an optimal temperature of 4$0^{\circ}C$, and an optimum pH of 7.0, and the thermal stability was observed the above 50% at 10$0^{\circ}C$ after 1 hour, and the stable range of pH was 6.0 to 8.0. The enzymatic activity was increased in the presence of 10 mM 2-mercaptoethanol, slightly by 10 mM SnCl2.2H2O.FeCl2.4H2O.CuCl2.2H2O.HgCl2.6H2O and SDS. End products from soluble starch were glucose, maltose and maltotriose, and Km value for soluble starch was 2.5mg/ml.

• Journal of Food Hygiene and Safety
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• v.33 no.3
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• pp.168-175
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• 2018

The use of microwave-assisted extraction and an acid-base clean-up process to determine the amount of methylmercury (MeHg) in marine products was suggested in order to improve the complicated sample preparation process. The optimal conditions for microwave-assisted extraction was developed by using a 10% NaCl solution as an extraction solution, setting the extraction temperature at $50^{\circ}C$, and holding for 15 minutes to extract the MeHg in marine products. A NaOH solution was selected as a clean-up substitute instead of L-cysteine solution. Overall, 670 samples of marine products were analyzed for total mercury (Hg). Detection levels were in the range of $0.0006{\sim}0.3801{\mu}g/kg$. MeHg was analyzed and compared using the current food code and the proposed method for 49 samples which contained above 0.1 mg/kg of Hg. Detection ranges of methylmercury followed by the Korea Food Code and the proposed method were $75.25(ND{\sim}516.93){\mu}g/kg$ and $142.07(100.14{\sim}244.55){\mu}g/kg$, respectively. The total analytical time of proposed method was reduced by more than 25% compared with the current food code method.

• Journal of Preventive Medicine and Public Health
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• v.32 no.2
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• pp.170-176
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• 1999

Objectives: To evaluate the protective effects of glutathione (GSH) on the cytotoxicity of mercurial compounds$(CM_3HgCl,\;HgCl_2)$ or cadmium chloride$(CdCl_2)$ in EMT-6 cells. Methods: The compounds investigated were $CH_3HgCl,\;HgCl_2,\;CdCl_2$, GSH, buthionine Sulfoximine(BSO), L-2-oxothiazolidine-4-carboxylic acid(OTC). Cytotoxicity analysis consist of nitric oxide(NO) production, ATP production and cell viability. Results: Mercurial compounds and cadmium chloride significantly decreased cell viability and the synthesis of NO and cellular ATP in EMT-6 cells. GSH was not toxic at concentrations of 0-1.6 mM. In the presence of GSH, mercurial compounds and cadmium did not decrease the production of ATP and nitrite in EMT-6 cells. The protective effects of GSH against the cytotoxicity of mercurial compounds and cadmium depended on the concentration of added GSH to the culture medium for EMT-6 cells. We evaluated the effects of intracellular GSH level on mercury- or cadmium-induced cytotoxicity by the pretreatment experiments. Pretreatment of GSH was not changed ${NO_2}^-$ and ATP production, and pretreatment of BSO was decreased in dose and time-dependent manner. Pretreatment of OTC was increased ${NO_2}^-$ and ATP production in dose- and tine-dependent manner. Because intracellular GSH level was increased by OTC pretreatment, the protective effect on mercury- and cadmium-induced cytotoxicity was increased. Conclusions: These results indicated that sulfhydryl compounds had the protective effects against mercury-induced cytotoxicity by the intracellular GSH levels.

• Korean Journal of Food Science and Technology
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• v.34 no.4
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• pp.541-545
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• 2002

Stability of Monascus pilosus pigment was investigated under various conditions. The concentration of the pigments stored under air and sub-atmosphere (250 mmHg) for 30 days at room temperature decreased by 77.9% and 48.4%, respectively. The pigment solution was stable under temperature ranges of $20-80^{\circ}C$, pH 4-8, darkness and presence of KCl, NaCl, $CaCl_2$, $MgCl_2$, and $ZnCl_2$. In contrast, the pigment solution was relatively unstable, decreasing in concentration by 6.0 and 11.6% at 100 and $121^{\circ}C$, 15.5 and 13.7% at pH 3 and 9, 22.9 and 66.8% under fluorescence and sun light, respectively, and 20.2% in the presence of $AlCl_3$.

• Journal of Environmental Health Sciences
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• v.15 no.2
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• pp.33-40
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• 1989

Dichromate reflux method for COD analysis is one of the useful and precise way to solve the organic content of the wastewater. But the standard procedure for COD is not entirely satisfactory for sample containing appreciable amounts of inhibiting substance, especially chloride ion. Under the conditions of the established test, a big disadvantage of the method is that dichromate oxidizes chloride quantitatively to chlorine. When it is necessary to use silver sulfate as a catalyst in the COD procedure, chloride must be removed before the addition of the catalyst. Silver sulfate and mecuric sulfate forms a precipitate of AgCl and HgCl$_{2}$ separately which is not completely oxidized during the test and, therefore, cannot be corrected for. So, we evaluate and compensate the amount of chloride oxidation in the absence of chemicals during the experimental procedure. Calculation of COD is made using the following reviced formula: real COD = tested COD - 0.2277Cl.