• Journal of Korean Society for Atmospheric Environment
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• v.12 no.4
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• pp.399-406
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• 1996

Acidic fog is catastrophic to aviation and potentially affect materials, vegetation, crops and public health. This paper was carried out to investigate the chemical features of fog sample at Mt. Sobaek (mean sea level : 1, 340m) from June to August 1995. Each sample was analyzed for pH, electrical conductivity and major ions (anion : $Cl^N)_3^-, SO_4^{2-}, cation : Na^+, NH_4^+, K^+, Mg^{2+}, Ca^{2+}$) by ion chromatography. The quality analysis of fog sample data was performed based on ion balance and electrical conductivity method. The wind directions are subdivided into the northerly and southerly wind according to the wind direction data at the Sobaek-san meteorological observation station. Statistical analyses were performed on the complete set of results in order to obtain a description of fog sample. All the statistical treatment was carried out using the SPSS/PC + software package. The major ion concentration of fog samples was higher for the northwesterly wind cases than sourtheasterly wind cases. The pH of fog sample varied between 2.95 and 6.08. The average pH and electrical conductivity of total sample (n=210) were 4.39 and 113.0 $\mu$S/cm, respectively. It may be noted that in nearly all the cases, the dominant major ions in the fog sample at Mt. Sobaek were $SO_4^{2-}, NO_3^-, H^+ and NH_4^+$.

• Applied Chemistry for Engineering
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• v.34 no.6
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• pp.626-632
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• 2023

Acemannan, a highly acetylated glucomannan, was extracted from fresh Aloe vera leaves by ethanol fractionation, resulting in a concentration increase of more than threefold. The presence of acemannan was confirmed using FTIR and ¹H NMR analysis, revealing an average molecular weight of 780 kDa. The flocculating activity of the fractionated aloe gel polysaccharide was assessed through settling tests in a 1% (w/v) bentonite suspension. The results demonstrated that the aloe polysaccharide exhibited remarkable stability within a temperature range of 20~70 ℃. The maximal flocculation rate at different pH levels ranged from 93% to 97%, with an optimal dose for maximum flocculation rate between 0.25 mg/mL. Notably, the minimum dose required for flocculation was achieved at a pH of 3, attributed to the compression of electrostatic repulsion on the surface of bentonite particles. However, the flocs obtained under acidic conditions were less dense and compact, exhibiting lower sedimentation velocity compared to those formed under neutral and alkaline pH conditions. Additionally, the addition of salt showed a slight synergistic effect on flocculation, significantly enhancing the sedimentation velocity. This investigation highlights the potential of Aloe vera polysaccharide as a natural and edible flocculant, offering promising applications in various industries.

• Microbiology and Biotechnology Letters
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• v.50 no.2
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• pp.211-217
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• 2022

Sodium hypochlorite (NaClO) is a disinfectant widely used in hospitals and food industries because of its antimicrobial activity against not only bacteria but also fungi and virus. The antibacterial activity of NaClO lies in the maintenance of a stable hypochlorous acid (HClO) concentration, which is regulated by pH of the solution. HClO can easily penetrate bacterial cell membrane due to its chemical neutrality and the antibacterial activity of NaClO is thought to depend on the concentration of HClO in solution rather than hypochlorite ions (ClO^-). In this study, we investigated the antibacterial activity of NaClO according to pH adjustment by means of time kill test and assays of Reactive Oxygen Species (ROS) and adenosine triphosphate (ATP) concentration changes before and after NaClO treatment. We also investigated that the degree of cell wall destruction through field emission scanning electron microscopy (FE-SEM). Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) exposed to 5 ppm NaClO at pH 5 exhibited 99.9% mortality. ROS production at pH 5 was 48% higher than that produced at pH 7. In addition, the ATP concentration in E. coli and S. aureus exposed to pH 5 decreased by 94% and 91%, respectively. As a result of FE-SEM, it was confirmed that the cell wall was destroyed in the bacteria by exposing to pH 5 NaClO. Taken together, our results indicate that the antibacterial activity of 5 ppm NaClO can be improved simply by adjusting the pH.

• Korean Journal of Materials Research
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• v.13 no.4
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• pp.251-258
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• 2003

The effects of the salt and the precursor pH on the synthesizing behavior and the morphology of mullite have been studied. Two kinds of mullite precursor sols were prepared by the dissolution of two kinds of salt (aluminum nitrate enneahydrate, Al($NO_3$)$_3$ㆍ$9H_2$O; type I and aluminum sulfate 14∼18 water, (SO$Al_4$)$_3$$\cdot$$14∼18H_2$O; type II) into the mixture of colloidal silica sol, respectively. Precursor pH of the sols was controlled to the acidic (pH= 1.5∼2) and basic (pH= 8.5∼9) conditions. The co-products with nitrate and sulfate were completely eliminated at $500^{\circ}C$ and $850^{\circ}C$, respectively, which was confirmed by TG/DTA results. The synthesizing temperature of mullite phase was found to be above $1200^{\circ}C$ for pH= 1.5∼2 and above $1300^{\circ}C$ for pH= 8.5∼9 in type I. However, in type II, the synthesizing temperature of mullite was decreased to $850^{\circ}C$ for pH= 1.5∼2 and $1100^{\circ}C$ for pH= 8.5∼9. The grain size of the mullite synthesized at pH= 8.5∼9 was larger than that at pH= 1.5∼2 in overall heat-treated temperatures, showing smaller grain size in type II. Aspect ratio of the mullite grains was more increased at pH= 1.5∼2 than pH= 8.5∼9 in type I, showing similar aspect ratio at both pH conditions in type II. It was found that the synthesizing temperature and grain size were predominantly governed by the initial precursor pH and decomposition of the salt, with minor effect on the grain morphology.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.1
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• pp.125-129
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• 1994

A field survey was carried out in Korea to assess the mineral composition of rice straw since it is a cheap and available cattle feedstuff. Forage and soil samples were collected in 4 localities in the Kyongbuk province. Soil analysis were also carried out in order to establish the relationships between soil composition and mineral content in the rice straw. Based on NRC tables, the rice straw samples provided adequate amounts of Mg, Ca, K, S, Mo, Mn and Zn. Percentages of samples deficient in P, Na, Cu and Se were 83, 50, 67 and 83 respectively. Soil samples, whose mean pH was 5.8 and mean organic matter content was 3.99%, were comparatively acidic and had high organic matter content. They also had high amounts of extractable Fe and Mn. Correlation coefficients between mineral content in soil and rice straw were low, i.e., 0.42 for Me (p < 0.05), and 0.37 for Mo (p < 0.05). The low or nonexistent correlation between soil and forage composition indicates the difficulty of establishing appropriate methods of mineral availability to the plants.

• Mycobiology
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• v.37 no.4
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• pp.313-316
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• 2009

To determine the optimal medium conditions for the detection of the cellulolytic activity in Ganoderma lucidum, we varied three media conditions: dye reagent, pH, and temperature. First, we evaluated the use of four dyes, Congo Red, Phenol Red, Remazol Brilliant Blue, and Trypan Blue. To observe the effect of pH on the chromogenic reaction, we also made and tested various media spanning acidic and alkaline pHs, ranging from 4.5 to 8.0. Furthermore, in order to research the effect of temperature on the clear zone and the fungus growing zone, we tested temperatures ranging from 15 to $35{^{\circ}C}$. On the whole, the best protocol called for Ganoderma lucidum transfer onto media containing Congo red with pH adjusted to 7.0, followed by incubation at $25{^{\circ}C}$ for 5 days. Our results will be useful to researchers who aim to study extracellular enzyme activity in Ganoderma lucidum.

• Food Science of Animal Resources
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• v.25 no.3
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• pp.357-364
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• 2005

To search probiotic microorganisms, we isolated Lactobacillus sp. from kefir, The Lactobacillus sp. strain showed $99.5\%$ of identity to species Lactobacillus rhamnosus by API kit. Lactobacillus rhamnosus showed high resistances to acidic environment, which grew well even at pH 2.0 and $1.0\%$ bile salt Enzyme activity of Lactobacillus rhamnosus was higher in amylase ($0.673\;{\mu}mol/min/mg$) than that in xylanase ($0.288\;{\mu}mol/min/mg$), cellulase($0.117\;{\mu}mol/min/mg$) and phytase($0.269\;{\mu}mol/min/mg$). Especially, the Lactobacillus rhamnosus showed high heat stability which remained $1{\times}10^6\;CFU/ml$ at $60^{\circ}C$. The maximum numbers of Lactobacillus rhamnosus on growth owe was reached at 24 h fermentation and pH was decreased to 4.6. The resistances of Lactobacillus rhamnosus to acidic pH and bile salt were better than that of Lactobacillus acidophilus used as control. When Lactobacillus rhamnosus was cultured with E. coli in MRS broth, E. coli was disappeared after 18 h. These result suggest that the isolated Lactobacillus rhamnosus has a useful probiotics properties.

• Journal of Microbiology and Biotechnology
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• v.27 no.3
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• pp.507-513
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• 2017

Bacillus subtilis spores can be used for protein display to engineer protein properties. This method overcomes viability and protein-folding concerns associated with traditional protein display methods. Spores remain viable under extreme conditions and the genotype/phenotype connection remains intact. In addition, the natural sporulation process eliminates protein-folding concerns that are coupled to the target protein traveling through cell membranes. Furthermore, ATP-dependent chaperones are present to assist in protein folding. CotA was optimized as a whole-cell biocatalyst immobilized in an inert matrix of the spore. In general, proteins that are immobilized have advantages in biocatalysis. For example, the protein can be easily removed from the reaction and it is more stable. The aim is to improve the pH stability using spore display. The maximum activity of CotA is between pH 4 and 5 for the substrate ABTS (ABTS = diammonium 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate). However, the activity dramatically decreases at pH 4. The activity is not significantly altered at pH 5. A library of approximately 3,000 clones was screened. A E498G variant was identified to have a half-life of inactivation ($t_{1/2}$) at pH 4 that was 24.8 times greater compared with wt-CotA. In a previous investigation, a CotA library was screened for organic solvent resistance and a T480A mutant was found. Consequently, T480A/E498G-CotA was constructed and the $t_{1/2}$ was 62.1 times greater than wt-CotA. Finally, E498G-CotA and T480A/E498G-CotA yielded 3.7- and 5.3-fold more product than did wt-CotA after recycling the biocatalyst seven times over 42 h.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.3
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• pp.390-395
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• 2005

Reported here are the effects of added formic acid on inhibitory effect of Salmonella gallinarum in poultry feed. Two experiments were conducted to investigate the viability of S. gallinarum and pH of poultry feed using different dietary formic acid levels (0.0, 0.5, 1.0 and 1.5%) on inhibitory effect of S. gallinarum in broiler feed. Experiment one was conducted to investigate the viability of S. gallinarum and pH of artificially contaminated diet at 0, 1, 3, 5 and 7 days after treatment in vitro. Formic acid showed a significant (p<0.05) reduction in the viability for all treatments with time after treatment. Various formic acid levels in vitro showed a reduction in the pH of the diet depending upon the concentration of treated acid, and the diet remained acidic below the growth range of S. gallinarum. This meant that the bacterial cells were exposed to stressful conditions that made them unable to grow. Experiment two was conducted to find out the effect of dietary formic acid levels on S. gallinarum colonization and pH in the contents of crop, small intestine, large intestine and ceca and mortality rate of broiler chicks at 7, 14 and 21 days of age when fed artificially contaminated diet with S. gallinarum. The numbers of S. gallinarum re-isolated from all treated groups except in groups treated with 0.5% formic acid, decreased significantly (p<0.05) compared with the control group. The treatment significantly (p<0.05) lowered the pH of the crop, small intestine, large intestine and ceca contents in all groups except the groups treated with 0.5% formic acid compared with the control. All treated groups showed a significant (p<0.05) reduction in overall mortality rate during the experimental period (3 to 21 days) compared with the control. The results indicate that addition of formic acid in a total concentration of 1.5% to the diet of newly hatched broiler chicks significantly decreases the contamination of diet with S. gallinarum.

• Journal of Korean Society of Forest Science
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• v.87 no.3
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• pp.429-444
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• 1998

Objective of this study was to select ectomycorrhizal fungi for black spruce(Picea mariana) inoculation to overcome the growth inhibitory effects of Kalmia angustifolia. Nineteen isolates representing 11 species of ectomycorrhizal fungi were tested for their abilities to grow and form mycorrhizae with black spruce seedlings in the presence of water leachate of leaves of Kalmia. Mycelium growth of 9 isolates were inhibited by the leaf leachate. Colony diameter and biomass of the other 10 isolates were either increased or unaffected under the same conditions. Acidic pH of the culture medium(pH 3 and 4) inhibited some of the fungi, but a combination of acidic pH and the leaf leachate was more inhibitory. Thirteen isolates were able to form ectomycorrhizae with black spruce in presence of 25% leaf leachate in pure culture. Four isolates, Paxillus involutus(NF4), Cenococcum geophilum(GB12), Laccaria laccata(GB23), and E-strain(GB45) formed mycorrhizae more successfully than the others in presence of up to 50% Kalmia leaf leachate. Black spruce seedlings pre-inoculated with these fungi were grown with Kalmia leaf leachate and live Kalmia plants during a four month greenhouse experiment. Abundant mycorrhizae(77-91% of root tips) were developed on seedlings pre-inoculated with P. involutus, L. laccata and E-strain but relatively poor mycorrhization(32% of root tips) resulted with C. geophidum. Over 90% of the short root mycorrhizae were attributed to the inoculated fungi although indigenous mycorrhizae also occurred on most seedlings. Persistence of the mycorrhizae was not affected by living Kalmia plants. Over 80% of the mycorrhizae on seedlings inoculated with P. involutus, L. laccata and E-strain and 53% of the mycorrhizae on seedlings inoculated with C. geophilum were attributable to the inoculant fungi. Control seedlings formed about 45% ectomycorrhizal short roots with indigenous fungi. The L. laccata and C. geophilum inoculated seedlings exhibited enhanced mycorrhizae formation in presence of Kalmia leaf leachate. Mycorrhizae formation with inoculant fungi was 4-15% lower at pH 4 than at pH 5, with the greatest inhibition occurring for L. laccata. Seedlings inoculated with P. involutus had the greatest shoot and root growth followed by L. laccata and E-strain inoculated seedlings. The P. involutus and L. laccata inoculated seedlings were significantly taller with more shoot dry biomass than the uninoculated(control) seedlings. E-strain inoculated seedlings had significantly higher shoot dry biomass and significantly lower number of first order lateral roots compared to the control but other growth parameters such as height, root dry weight and number of short root tips were not significantly different from the control. Seedlings inoculated with C. geophilum were not significantly different from the uninoculated seedlings in any of the growth parameters except for the number of first artier lateral roots which was significantly less than the control seedlings.