• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.2
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• pp.153-159
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• 2017

We examined changes in the physiological responses of gray mullet Mugil cephalus exposed to acidic seawater (pH 6.0, 6.5, 7.0) and normal seawater (pH 8.0, control) for 15 days. As pH decreased, survival rate and body weight also decreased. Levels of aminotransferase, total protein and triglycerides also differed significantly with changes in pH, presumably due to stress caused by exposure to acidic water. The level of osmotic pressure was significantly higher in the pH 6.0 group than in other groups. Superoxide dismutase was significantly higher in the pH 6.5 and 7.0 groups than in the pH 8.0 group, and glutathione level was lowest in the pH 6.0 group. We conclude that decreasing the pH level of seawater induces a stress response in fish, damaging their ability to control their hematological and osmotic pressure. Antioxidant enzymes are generally sensitive to osmotic stress; in this study, antioxidant activity significantly changed with pH level. These results indicate that physiological stress induced by exposure to acidification reduces survival rates and inhibits growth in M. cephalus.

• Journal of Microbiology and Biotechnology
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• v.26 no.8
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• pp.1409-1419
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• 2016

The effect of pH on propionate degradation in an upflow anaerobic sludge blanket (UASB) reactor containing propionate as a sole carbon source was studied. Under influent propionate of 2,000 mg/l and 35℃, propionate removal at pH 7.5-6.8 was above 93.6%. Propionate conversion was significantly inhibited with stepwise pH decrease from pH 6.8 to 6.5, 6.0, 5.5, 5.0, 4.5, and then to 4.0. After long-term operation, the propionate removal at pH 6.5-4.5 maintained an efficiency of 88.5%-70.1%, whereas propionate was hardly decomposed at pH 4.0. Microbial composition analysis showed that propionate-oxidizing bacteria from the genera Pelotomaculum and Smithella likely existed in this system. They were significantly reduced at pH ≤5.5. The methanogens in this UASB reactor belonged to four genera: Methanobacterium, Methanospirillum, Methanofollis, and Methanosaeta. Most detectable hydrogenotrophic methanogens were able to grow at low pH conditions (pH 6.0-4.0), but the acetotrophic methanogens were reduced as pH decreased. These results indicated that propionate-oxidizing bacteria and acetotrophic methanogens were more sensitive to low pH (5.5-4.0) than hydrogenotrophic methanogens.

• Journal of Soil and Groundwater Environment
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• v.27 no.1
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• pp.25-30
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• 2022

Mackinawite (FeS), as a ubiquitous reduced iron mineral, is known as a key controller of redox reactions in anaerobic subsurface environment. The reaction of FeS with redox-sensitive toxic element such as arsenic is substantially affected by pH conditions of the given environments. In this study, the interaction of As(V) with FeS was studied under strict anaerobic conditions with various pH conditions. The pH-dependent arsenic removal tests were conducted under wide ranges of pH conditions and X-ray absorption spectroscopy (XAS) was applied to investigate the reaction mechanisms under pH 5, 7, and 9. The removal efficiency of FeS for As(V) showed the higher removal of As(V) under low pH conditions and its removal efficiency decreased with increasing pH, and no As(V) reduction was observed in 1 g/L FeS solution. However, XAS analysis indicated the reduction of As(V) to As(III) occurred during reaction between FeS and As(V). The reduced form of As(III) was particularly identified as an arsenic sulfide mineral (As₂S₃) in all pH conditions (pH 5, 7, and 9). As₂S₃ precipitation was more pronounced in pH 5 where the solubility of FeS is higher than in other pH conditions. The linear combination fitting results of XAS demonstrated that As(V) removal mechanism is concerted processes of As₂S₃ precipitation and surface complexation of both arsenic species.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.283.2-283.2
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• 2003

This study established a highly sensitive novel quantification method for detecting felodipine in human plasma using LC-MS/MS. The mobile phase used after degassing was composed of 1 mM ammonium acetate and acetonitrile (20:80, pH 6.0), with flow rate of 200 uL/min. One mL plasma were pipetted into glass tubes and spiked with 0.1 mL of internal standard solution. (omitted)

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.352-357
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• 2019

In this study, a reactive emulsifier with vinyl groups was synthesized by using 3-butenoic acid and polyoxyethylene(20) stearyl ether. The synthesized reactive emulsifier was confirmed by FT-IR and $^1H-NMR$. In addition, the reactive emulsifier synthesized in the preparation of aqueous acrylic pressure sensitive adhesives was used and the properties of the respective pressure sensitive adhesives were compared to those of using commonly used nonionic emulsifiers. The solid content was measured in the range of 56.8~57.4%. In the case of the initial adhesion, the S20BA made with a reactive emulsifier was measured as $^{\sharp}13$. Peel strengths of the prepared adhesives were measured in the range of $0.66{\sim}1.05kg_f$ and the highest peel strength was observed for S20BA. As a result of the heat resistance test, S20BA showed the highest as $840^{\circ}C$. In order to evaluate the applicability of adhesives for skin, the pH value was measured as 7, neutral and also it was found to be non-irritation from primary skin irritation test results.

• Applied Biological Chemistry
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• v.37 no.5
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• pp.414-420
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• 1994

Birnessite, pyrolusite and hausmannite were synthesized and tested for the ability to oxidize Cr(III) to Cr(VI). These oxides differed in zero point of charge, surface area, and crystallinity. The kinetic study showed that Cr(III) oxidation on the Mn-oxide surface is a first-order reaction. The reaction rate was various for different oxide at different conditions. Generally the reaction by hausmannite, containing Mn(III), was faster than the others, and oxidation by pyrolusite was much slower. Solution pH and initial Cr(III) concentration had a significant effect on the reaction. Inhibited oxidation at higher pH and initial Cr(III) concentration could be due to the chance of Cr(III) precipitation or complexing on the oxide surface. Oxidations by birnessite and hausmannite were faster at lower pH, but pyrolusite exhibited increased oxidation capacity at higher pH in the range between 3.0 and 5.0. Reactions were also temperature sensitive. Although calculated activation energies for the oxidation reactions at pH 3.0 were higher than the general activation energy for diffusion, there is no experimental evidence to suggest which reaction is the rate limiting step.

• Korean Journal of Mineralogy and Petrology
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• v.37 no.2
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• pp.47-57
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• 2024

Jarosite, a mineral belonging to the alunite family, is found in various low pH environments and can incorporate cations or oxyanions into its structure, either by coprecipitation or substitution. This mineral is sensitive to pH changes and can easily transform into goethite upon geochemical changes, such as an increase in pH. This transformation can release toxic ions from the jarosite, potentially causing additional environmental damage. In addition to potassium (K), sodium (Na) and ammonium (NH₄) can also substitute for cations in jarosite. The formation of jarosites containing these and other cations is significant not only for acid mine drainage but also for the smelting industry. In this study, three different types of jarosites containing various cations were synthesized and the phase transformation of each jarosite to goethite upon pH change were compared. All the jarosites were sensitive to pH changes, showing much higher rates of phase change at pH 8 than at pH 4. At the relatively low pH of 4, the phase transformation of K-jarosite, which is most stable in structure, to goethite was the slowest. For the other two jarosites, the cations have either smaller or larger radii than K ions, resulting in differences in structural stability and they showed more rapid transformations to goethite. However, at pH 8, K-jarosite exhibited a much more rapid transformation to goethite than the other jarosites, which was also evident from the rapid increase in K ions in aqueous solution. The mineral transformation behavior of K-jarosite at higher pH is significantly different from that at lower pH, indicating that the mechanism of the transformation to goethite differs between these conditions, which requires further investigation. The results of this study indicate that the mineral transformation of jarosite in acid mine drainage or smelter waste disposal may significantly influence the behavior of heavy metals. This research provides valuable insights for predicting the behavior of heavy metals in smelting industry waste disposal.

• Journal of Food Hygiene and Safety
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• v.4 no.2
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• pp.155-163
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• 1989

Three species of lactobacilli (L. casei, L. acidophilus, L. bulgaricus) were tested for their antibacterial activity. They all were antagonistic to growth of enteropathogenic Escherichia coli and Salmonella enteritidis in associative cultures in YS-medium (0.1 % yeast extract + skimmilk). Sal. enteritidis was more sensitive to the inhibition than was E. coli. Control cultures of E. coli and Sal. enteritidis were pH 5.08 and 5.70 in 72 hrs of incubation and the associative cultures were pH 3.35-4.48. The increases in pH resulting from growth of the lactobacilli in the associative cultures appeared to be sufficient and mainly responsible for the antagonistic actions exerted on the pathogens.

• KSBB Journal
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• v.15 no.5
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• pp.444-451
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• 2000

Nonliving methanotrophic biomass was used as biosorbent to remove lead which is one of representative pollutants in metal-bearing wastewater. Solution pH, maximum uptake, biosorbent dose and ionic strength were considered as major factors for adsorption experiments. The optimum pH range for lead removal was increased 3.8∼11.0 for methanotrophic biomass compared to biosorbent-free control, pH of 8.4∼11.2. Removal efficiency of lead by methanotrophic biomass was pH dependent, but less sensitive than that of control. In isotherm experiments with 0.2g biosorbent/L at initial solution pH 5.0, methanotrophic biomass took up lead from aqueous solutions to the extent of 1085 mg/g biomass. Removal amount of lead increased with an increase of biomass dose. According to biomass dose for initial 1000 mg Pb/L at initial pH 5.0, the optimum amount of biomass for maximum lead removal per unit methanotrophic biomass was 0.2 g biomass/L. As a result of scanning electron microscope (SEM) micrographs equipped with energy dispersive spectroscopy (EDS), lead removal by methanotrophic biomass seemed to be through adsorptions on the surface of methanotrophic biomass and exopolymers around the biomass. EDS spectra confirmed that lead adsorption appeared on the biomass and exopolymers that may be effective to lead removal comparing before and after contact with lead. Removal efficiency of lead was slightly affected by ionic strength up to 2.0 M of NaCl and NaNO$_3$respectively.

• Molecules and Cells
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• v.39 no.1
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• pp.46-52
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• 2016

It is increasingly apparent that nature evolved peroxiredoxins not only as $H_2O_2$ scavengers but also as highly sensitive $H_2O_2$ sensors and signal transducers. Here we ask whether the $H_2O_2$ sensing role of Prx can be exploited to develop probes that allow to monitor intracellular $H_2O_2$ levels with unprecedented sensitivity. Indeed, simple gel shift assays visualizing the oxidation of endogenous 2-Cys peroxiredoxins have already been used to detect subtle changes in intracellular $H_2O_2$ concentration. The challenge however is to create a genetically encoded probe that offers real-time measurements of $H_2O_2$ levels in intact cells via the Prx oxidation state. We discuss potential design strategies for Prx-based probes based on either the redoxsensitive fluorophore roGFP or the conformation-sensitive fluorophore cpYFP. Furthermore, we outline the structural and chemical complexities which need to be addressed when using Prx as a sensing moiety for $H_2O_2$ probes. We suggest experimental strategies to investigate the influence of these complexities on probe behavior. In doing so, we hope to stimulate the development of Prx-based probes which may spearhead the further study of cellular $H_2O_2$ homeostasis and Prx signaling.