• Applied Biological Chemistry
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• v.34 no.1
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• pp.67-74
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• 1991

In order to improve the productivity of ethanol by sugar-alcohol-tolerant Saccharomyces cerevisiae D1, the effect of addition of $Ca^{2+}$ on the alcohol fermentation was investigated. The addition of $Ca^{2+}$led to both the improvement of ethanol productivity and the increase of viable cell concentration. The optimal concentration of $Ca^{2+}$ was 0.8 mM. The higher was initial concentration of glucose, the greater effect of $Ca^{2+}$ was observed. Ethanol inhibition of growth, specific death rate in lethal concentration of ethanol, and extracellular final pH decreased by the addition of $Ca^{2+}$. The effect of $Ca^{2+}$ supplementation was explained by the increase of its ethanol tolerance.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.634-640
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• 2015

Chelating agents have been proposed to improve the efficiency of phytoextraction of heavy metal hyperaccumulator. However, little studies to elucidate mechanism of chelating agents to increase cadmium (Cd) extractability have been conducted. The objectives of this study were to evaluate effect of different chelating agents on Cd extractability and to determine mechanism of Cd mobilization affected by these agents. An arable soil was spiked with inorganic Cd ($CdCl_2$) to give a total Cd concentration of $20mgCdkg^{-1}$. Ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) were selected and mixed with the arable soil at the rates of 0 and $5mmolkg^{-1}$. The mixture soils were incubated at $25^{\circ}C$ for 4 weeks in dark condition. Concentration of F1 Cd fractions (water soluble) significantly increased with addition of EDTA but did not changed with addition of CA. Especially; concentration of F5 Cd fractions (residual) significantly increased with addition of CA. Increase in water soluble with EDTA might be attributed to complexation of Cd and EDTA. Dissolved organic carbon concentration significantly increased with EDTA addition, but did not with CA implying that considerable amount of CA was decomposed to inorganic carbon by microorganism. Log activity of carbonate ($CO_3{^{2-}}$) which might be generated from CA increased with addition of CA. Increase in residual Cd fraction might be due to precipitation of Cd as $CdCO_3$. As a result, EDTA was effective in increasing Cd extractability, by contrast CA had significant effect in reducing Cd extractability.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1580-1581
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• 2008

We investigated the effects of intermittent hydrostatic pressure with various duration of resting period on changes in calcium ($Ca^{2+}$) concentration and adhesive forces of cells on substrates. The quantitive adhesive forces of cells were measured under various resting periods. When the pressure applied to the cells, the concentration of $Ca^{2+}$ increased. Under intermittent hydrostatic pressure, the concentration of $Ca^{2+}$ was maintained under a resting period of 15 min, while it was not decreased with other resting periods of less than 15 min. With a resting period of 15 min, the magnitudes of adhesive forces were significantly increase. In addition, the adhesive forces were measured with and without $Ca^{2+}$ chelating agents to evaluate the effect of $Ca^{2+}$ on cell adhesiveness. When $Ca^{2+}$ ions were chelated, the adhesive forces dramatically decreased, even under intermittent hydrostatic pressure. We conclude that $Ca^{2+}$ plays an crucial role in modulating the adhesive forces of cells, and that the concentration of $Ca^{2+}$ can be increased by intermittent hydrostatic stimuli.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.843-853
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• 1997

The effect of dopant on microwave dielectric properties of (1-x)MgTiO3-xCaTiO3 ceramics, known to be used as microwave dielectric resonators for global positioning system and personal communication system, has been analyzed in terms of variations in defect concentrations and microstructural features with its addition. The addition of dopants was revealed to result in a significant change in the microstructure as well as defect concentration of the ceramics. For instance, the quality factor is proportional to sintered density of the ceramics by inversely proportional to grain size as well as vacancy concentration. Accordingly, it is believed that the dopant effect on the microwave dielectric properties should be separately analyzed with either microstructural change or the change in vacancy concentration.

• The Korean Journal of Food And Nutrition
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• v.7 no.3
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• pp.177-182
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• 1994

The effect of phosphate salt (NafHP04) and sodium citrate on the emulsion stability of soy protein isolate (SPI) in the presence of calcium was investigated in terms of salt concentration and addition order. Both phosphate and citrate salts decreased the solubility of SPI despite their pH enhancing effects. Addition of calcium chloride (CaCl2) significantly decreased ES, which showed nearly negligible at more than 3 mM CaCl2 concentration. When Na2HP04 were added in the presence of 5 mM Cac12, 55 greatly increased up to 20mM concentration, above which however ES decreased. It was found that the addition order of Na2HPO4 and CaCl2 affected ES. The addition of phosphate and subsequent CaCl2 exhibited the higher 55 than the reverse order. In both cases, the overall ES profile was found to be nearly similar to the solubility profile of SPI, indicating the positive relationship between solubility and emulsion stability of SPI in the presence of calcium. Similar trend to the phosphate effect on ES was also observed for sodium citrate in the presence of calcium.

• Journal of the Korean Ceramic Society
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• v.31 no.12
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• pp.1417-1422
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• 1994

Effect of MgO, CaSO4, and CaF2 addition on the formation of clinker minerals in portland cement have been investigated by measuring the amounts of free-CaO and C3S in the fired specimens and analyzing the Mg and S concentration in C3S and C2S. It was found that CaSO4 inhibited C3S formation but MgO addition offset this effect of CaSO4. MgO addition also enhanced the mineralizing effect of CaSO4+CaF2, resulting in the acceleration of C3S formation. It was suggested that Mg might inhibit the formation of sulphate compounds rim around C2S and thus C2S+CaOlongrightarrowC3S reaction was facilitated.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.1
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• pp.49-55
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• 1999

The effect of fat supplementation of high calcium (Ca) diets on the performance, intestinal pH, body composition and size and weight of organs in growing chickens were investigated in two experiments. Growing chickens tolerated a high dietary level of Ca (22.5 vs 12.1 g/kg) in the presence of 6.3 g/kg of available phosphorus without any significant effect on performance. Intestinal pH was significantly increased by the addition of excess Ca and fat which probably created the right pH for the formation of insoluble Ca soaps. Excess dietary Ca increased carcass linoleic acid concentration at the expense of palmitic and stearic acid contents, whilst the addition of sunflower oil (80 g/kg diet) to the diet increased carcass linoleic acid concentration at the expense of palmitic acid content of the carcass. Intestinal and visceral organ size and weight were not influenced by excess Ca or fat. However, there was a non significant increase in the intestinal dry weight per unit of length caused by excess dietary Ca. It was concluded that excess dietary Ca of 22.5 g/kg did not significantly influence the performance of meat chickens. However, excess Ca increased intestinal pH and altered carcass fatty acid composition. Fat supplementation did not alter intestinal pH with high Ca diets. Excess dietary fat altered carcass fatty acid composition and reduced protein content. Intestinal and visceral organ size and weights were not influenced by excess dietary levels of Ca of fat.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.167-170
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• 2000

Proteolytic hydrolysis is one of the main enzymatic reaction of waste activated sludge (WAS) digestion. Pretense excreted from Bacillus stearothermophilus (ATCC 31197) showed optimum temperature of $75^{\circ}C$ for maxium heat stable proteolytic activity against azo casein. The dependency of $Ca^{2+}$, $Zn^{2+}$ on heat stability of proteolytic enzymes were measured with various concentrations. It was shown that $Ca^{2+}$ ion enhanced heat stability of these enzymes. Then thermophilic aerobic digestion (TAD) was performed using B. sterothermophilus with the addition of divalent ions. Performance of TAD process with ATCC 31197 activated by $Ca^{2+}$, $Zn^{2+}$ions in terms of dissolved organic carbon (DOC) concentration, extracellular protein concentration, and scanning electrion microscopy (SEM) analysis. The best result of protein reduction concentration in digestion test was obtained with the addition of 2 mM $Ca^{2+}$ ion.

• Journal of Environmental Science International
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• v.1 no.1
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• pp.69-76
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• 1992

The effects of $Ca_{2+}$ ion on the formation of micelle colloid of nonionic surfactants, nonylphenol-(ethylene oxide)n [NP-(EO)n: n= 11, 40, 100) were investigated by the iodine solubilization method. The characteristics of spectra depended on the concentration of $Ca_{2+}$ ion and the number of EO unit. Above CMC(critical micelle concentration), the intensity of the CT (charge transfer) band by the addition of $Ca_{2+}$ ion for the NP-(EO)11 and NP-(EO)40 increased and when decreased and for the NP-(EO)In continuously increased. The increase in the intensity of CT band were attributed to the compactness of micelle in the presence of $Ca_{2+}$ ion. These phenomena may be explained by the fact that the linear ethylene oxide (EO) chain, relatively free to assume various configuration in aqueous solution, could form a pseudo-crown ether structures capable of forming complexes with $Ca_{2+}$ ion.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.373-380
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• 1993

When the cells of yeast K35 were immobilized in Ca-alginate gel, cell concentration and viability decreased as alginate concentration increased. Considering the results, 2% (w/v) Ca-alginate concentration would be suitable. Among various concentrations of additives and cross-lin-king agent, the addition of 1.67% (w/v) of bentonite together with 0.33% (v/v) of glutaraldehyde (ABG bead) resulted in the highest ethanol production of 1.8%(w/v), using YPD medium containing 2% glucose. ABG bead seemed to be more resistant to phosphate ion than Ca-alginate bead. 0.33%(w/v) of phosphate was a proper concentration for the ethanol production by ABG bead. Scanning electron microscopic observation depicted that the immobilized cells on the bead surface were coated by alginate gel and that the cells in the internal bead were cross-linked with alginate matrix. When repeated-batch culture was performed with ABG bead for 40 days in a packed-bed reactor, ethanol concentration of about 90~110 g/l-gel was maintained. Cell viability was maintained around 70%, and outgrowing cell concentration was below 6.3% of total cell concentration. Consequently, the results showed that ABG head was a potential carrier for continuous production of ethanol compared to conventional Ca-alginate bead.