• Microbiology and Biotechnology Letters
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• v.19 no.1
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• pp.76-81
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• 1991

- The effect of redox potential (ORP) on lysine production by a leucine auxotrophic regulatory mutant of Corynebacterium glutclmicum on molasses medium was investigated in a 2-1 jar fermentor at pH 6.9 and $32^{\circ}C$. At a dilution rate of D=O.l $h ^1$, a maximum yield of Yr,,s=0.24 was obtained in either carbon- or leucine-limited chemostat where the redox potential was between -60 mV and - 100 mV. This level of redox potential corresponded to moderate oxygen deficiency. Under a high oxygen deficient condition of the redox potential of - 130 rnV (oxygen-limited chemostat), all the kinetic parameters such as $Y_[p/s}, q_s\; and \; q_p$ were decreased significantly and significant amounts of byproducts including glycine, alanine and valine were accumulated in the culture, indicating that the control of redox potential is important in lysine fermentation. At the redox potential of - 40 mV, on the other hand, large quantities of arginine (up to 0.38g/l) and glutamic acid (up to 0.12 g/l) were produced. A maximum lysine productivity of 2.41 g/l/h was achieved at - 66 mV under a carbon-limited condition.

• Corrosion Science and Technology
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• v.11 no.2
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• pp.56-64
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• 2012

Factors affecting corrosion of stainless steels such as pH, oxidation and redox potential (ORP), soil resistivity, water content of soil, chloride ion concentration, bacteria activity, and corrosion potential have been investigated using soil analysis, bacterial analysis, surfacial analysis, and analysis of corrosion potentials of several stainless steels buried in 8 sites of Seoul metropolitan for one year. Corrosion potential was affected by occurrance of corrosion as well as bacteria activity but the behavior of corrosion potential with time is different depending on occurrance of corrosion and bacteria activity. The main factor affecting corrosion of stainless steels in soil is level of chloride ion concentration which is also a main factor affecting corrosion of stainless steels in chloride containing drinkable water. Furthermore, guideline of stainless steels in drinkable water is concluded to be applicable to that in soil by the results from surfacial analysis.

• Journal of Environmental Science International
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• v.23 no.10
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• pp.1745-1753
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• 2014

Sediment microbial fuel cell (SMFC), equipped with Zn, Al, Cu, Fe or graphite felt (GF) anode and marine sediment, was performed. Graphite felt was used as a common cathode. SMFC was single chambered and did not use any redox mediator. The aim of this work was to find efficient anodic material. Oxidation reduction potential (ORP), cell voltage, current density, power density, pH and chemical oxygen demand (COD) were measured for SMFC's performance.. The order of maximum power density was $913mWm^{-2}$ for Zn, $646mWm^{-2}$ for Fe, $387.8mWm^{-2}$ for Cu, $266mWm^{-2}$ for Al, and $127mWm^{-2}$ for graphite felt (GF). The current density over voltage was found to be strongly correlated with metal electrodes, but the graphite felt electrode, in which relatively weaker electricity was observed because of its bio-oriented mechanism. Metal corrosion reactions and/or a complicated microbial electron transfer mechanism acting around the anodic compartment may facilitate to generate electricity. We presume that more sophisticated selection of anodic material can lead to better performance in SMFC.

• Korean Journal of Environmental Biology
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• v.17 no.2
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• pp.183-190
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• 1999

The bioleaching of heavy metals from fly ash was performed by Thiobacillus thiooxidans MET isolated from the enrichment culture of an anaerobically digested sludge. The effect of solid concentrations on the efficiency of metal leaching was studied in shaken flasks. In the range of solid concentrations 20 g.L­$^1$to 100 g.L­$^1$T. thiooxidans MET oxidized S$^{0}$ to sulfate without any lag period. The final pH of slurry solution was decreased to below pH 1, and the final oxide-redox potential (ORP) was increased to over 420 mV in the solid concentrations below 100 g.L­$^1$. However, the initial lag period of 4 to 8 days was required to obtain the pH reduction and ORP increase of the slurry solutions in the range of solid concentrations 150 g.L­$^1$to 300 g.L­$^1$. The sulfur oxidation rate of T. thiooxidans MET in 20~100 g.L­$^1$solid concentrations was 0.70~0.75 g-S.L­$^1$ㆍ d­$^1$, but its sulfur oxidation activity was remarkably inhibited with increasing solid concentration over 150 g.L­$^1$. Increasing fly ash solids concentration in the range of solids concentration 20 g.L­$^1$ to 200 g.L­$^1$decreased the removal efficiency of Zn, Cu, Mn, Cr and Pb. The solubilization of heavy metals from fly ash was strongly correlated with the pH value of slurry solution. When the pH of slurry solution was reduced to 3, the solubilization process of Zn, Cu and Mn started, and their solubilization efficiency of Zn, Cu and Mn was progressively increased below pH 2. However, the solubilization process of Cr and Pb started at pH 2.5 and 2.0, respectively.

• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.75-80
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• 2007

This study evaluated groundwater quality around an uncontrolled landfill in W sity, Korea, which was monitored for about two years (2005-2006). Parameters of concern include redox-sensitive indicators such as pH, DO, EC, ORP, DOC (dissolved organic carbon), NH3, NO3 and SO4. About 10 years have elapsed after closing dumping of municipal wastes in the landfill. Leachates showed widely varying concentrations in COD(136${\sim}$263 mg/L), T-N(121${\sim}$186 mg/L), and NH3-N(14${\sim}$369 mg/L). Groundwater at the immediate downgradient of the landfill showed weakly acidic pH condition but very high levels of EC (3,000-4,000 ${\mu}S/cm$), which indicated that the groundwater was largely affected by the landfill leachate. Cl, a conservative ion, showed over 200 mg/L at the landfill border, but a gradually decreasing level with distance from the landfill, representing dispersion and dilution (natural attenuation) due to mixing with surrounding groundwater and replenished rainwater. Redox potential showed negative value at the landfill border but it increased up to 350 mV at downgradient wells, which indicated conversion of redox condition from reducing oxic ones. Ammonia, was largely enriched at most of the monitoring wells and its level greatly exceeded drinking water standard. In summary, all the parameters evidenced occurrence of natural attenuation with distance and with time but further monitoring is still required.

• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.270-282
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• 2008

The yeast Saccharomyces cerevisiae has defense mechanisms identical to higher eukaryotes. It offers the potential for genome-wide experimental approaches owing to its smaller genome size and the availability of the complete sequence. It therefore represents an ideal eukaryotic model for studying cellular redox control and oxidative stress responses. S. cerevisiae Yap1 is a well-known transcription factor that is required for $H_2O_2$-dependent stress responses. Yap1 is involved in various signaling pathways in an oxidative stress response. The Gpx3 (Orp1/PHGpx3) protein is one of the factors related to these signaling pathways. It plays the role of a transducer that transfers the hydroperoxide signal to Yap1. In this study, using extensive proteomic and bioinformatics analyses, the function of the Gpx3 protein in an adaptive response against oxidative stress was investigated in wild-type, gpx3-deletion mutant, and gpx3-deletion mutant overexpressing Gpx3 protein strains. We identified 30 proteins that are related to the Gpx3-dependent oxidative stress responses and 17 proteins that are changed in a Gpx3-dependent manner regardless of oxidative stress. As expected, $H_2O_2$-responsive Gpx3-dependent proteins include a number of antioxidants related with cell rescue and defense. In addition, they contain a variety of proteins related to energy and carbohydrate metabolism, transcription, and protein fate. Based upon the experimental results, it is suggested that Gpx3-dependent stress adaptive response includes the regulation of genes related to the capacity to detoxify oxidants and repair oxidative stress-induced damages affected by Yap1 as well as metabolism and protein fate independent from Yap1.

• Journal of Environmental Science International
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• v.28 no.5
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• pp.511-520
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• 2019

This study was investigated to improve the phosphorus release and water quality by transformation of sedimentary P fraction for application of $CaO_2$. For the experiment, 0.5% (w/w) of $CaO_2$ was homogenized in the sediment and incubated with the control for 20 days. The analytical results showed that pH increased with $CaO_2$ and redox potential (ORP) was improved in the sediment of the reactor. The growth rate of chlorophyll-a was lower in the $CaO_2$ reactor and Dissolved Oxygen (DO) of overlying water maintained higher than that of the control. Total phosphorus (T-P) concentration in the overlying water increased from the initial concentration to 0.304mg/L in the control at 20 days. The reactor of $CaO_2$ was lowered by 29.3%. Ex-P, Fe-P and Ca-P in sediment P fraction were increased with the $CaO_2$. The formation of bound Fe-P and Ca-P in the sediments seemed to control the release of P by removing the Soluble Reactive Phosphorus (SRP) presented in the pore water. From the result, this indicated that the reduction of P release from the sediments seems to be effective in suppressing the eutrophication of P and improving the oxygen condition in the water quality with the application of $CaO_2$.