• Microbiology and Biotechnology Letters
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• v.26 no.4
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• pp.345-351
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• 1998

In an effort to develop a potent system for the production of various dp (degree of polymerization) chitooligosaccharides, 32 enzymes or microbial systems were screened for chitosanolytic acitivity using chitosan as a substrate. The efficiency of each enzyme system was evaluated by the changes of turbidity and viscosity of chitosan solution, the amount of precipitate and the reducing sugar-producing activity in the enzymatic reaction mixture. Based on these assay methods for the chitosanase activity, Bacillus sp. P2l out of 32 screened systems showed highly potent endochitosanase, which was comparable with a commercially available enzyme (E7). Chitooligosaccharides of dp 3-7 were separated by TLC as major enzymatic reaction products, suggesting that the chitosanase from Bacillus sp. P2l be endo-splitting type.

• Journal of the Korean Geotechnical Society
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• v.29 no.2
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• pp.23-34
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• 2013

An organic acid material, which can be manufactured by plants extraction, encourages microbe proliferation over time. Microbial activity, which is affected by organic acid, encourages accelerating consolidation with biochemical penetration; soil particles are compacted by microbes and pore water is dissipated quickly. Additionally, $CaCO_3$ for cementation was made by proliferating microbes. Accordingly, tests were conducted to investigate the unconfined compressive strength and permeability of soil samples aged with and without an organic acid. In the 96 days of aging, the strength was generally 1.5~2.5 times greater than those without an organic acid material and permeability was definitely decreased to 74.2~93.1%. SEM analysis showed the change of pore structure and the change of the total bacteria counts revealed the activity of microbes reflecting the engineering characteristics and this material would be an environment-friendly for soil improvement.

• Applied Biological Chemistry
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• v.41 no.5
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• pp.395-398
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• 1998

To develop the natural antibacterial agents which don't have any toxicity against man, collected several species of medicinal plants were tested for their antibacterial activity and inhibition effect on organic acids production from Streptococcus mutans. Among the tested medicinal plants, methanol extracts and n-hexane fraction of Juniperus rigida S. et Z. had the comparatively strong activities. For example, strong antibacterial effect against S. mutans were showed in methanol extracts, n-hexane and chloroform fractions. Organic acids production were reduced to 89.3 and 90.8% of control in methanol extracts and n-hexane fraction treated concentration of 1 mg/ml, respectively.

• Microbiology and Biotechnology Letters
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• v.7 no.4
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• pp.205-209
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• 1979

Lactobacillus acidophilus exhibited more growth and produced greater amounts of acid in the soy milk than Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillu helveticus examined. The supplementation of the soy milk with glucose accelerated the growth of L. acidophilus, and enhanced acid production by L. acidophilus whereas sucrose addition was without effect. The supplementation of the soy milk containing five percent glucose with a methionine accelerated the growth of L. acidophilus, and enhannced acid production by L. acidophilus. L. acidophilus showed greater population in the soy milk containing five percent glucose which was treated with 0.0008％ protease (9.40$\times$10$^{8}$ /m/) than the soy milk containing five percent glucose (2.02$\times$10$^{9}$ /ml) moreover L. acidophilus produced greater amounts of acid in the soy milk containing five percent glucose which was treated with 0.0008％ protease (1.47 ％) than in the soy milk containing five percent glucose (0.56％)

• Korean Journal of Food Science and Technology
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• v.18 no.2
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• pp.118-123
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• 1986

Soy milk prepared from soy protein concentrate was fermented with Lactobacillus acidophilus, L. bulgaricus, L. casci, Streptococcus lactis or S. cremoris. Growth and acid production of each organism in soy milk and flavor of soy yogurt beverages were investigated. Volatile compounds in soy milk and soy yogurts were also determined. Among the five organisms tested, L. bulgaricus produced most amount of acid in soy milk while S. cremoris produced least amount of acid in soy mile. Sensory evaluation showed that the flavor of soy yogurt beverages was inferior to that of milk yogurt beverage and the flavor of soy yogurt beverage prepared by L. bulgaricus was better than that of other soy yogurt beverages. Soy milk fermented with L. bulgaricus was more acceptable than unfermented soy milk. Lactic fermentation reduced n-hexanal in soy milk while it produced diacetyl that was not detected in unfermented soy milk.

• KSBB Journal
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• v.15 no.6
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• pp.615-620
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• 2000

To obtain quality germinated brown rices containing high levels of ${\gamma}$-aminobutyric acid (GABA), chitosan was applied during the brown rice germination. The GABA contents in germinated brown rices (1,035 nmole/g fresh weight) and brown rices germinated by water (771 nmole/g fresh weight) or by lactiv acid (728 nmole/g fresh weight). In addition to the enhancement of GABA, germination in the chitosan solution increased alanine concentration and decreased glutamic acid, aspartic acid and serine concentrations in the brown rices. The activity of glutamate decarboxylase was also enhanced by the chitosan treatment. Furthermore, germination by chitosan reduced fungal contamination markdely, compared with germination by water or germination by lactic acid. These results suggest that quality germinated brown rices containing high levels of GABA can be obtained by chitosan application.

• Korean Journal of Food Science and Technology
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• v.7 no.4
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• pp.238-242
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• 1975

The effects of various antimicrobial agents on the production of organic acid and saccharifying amylase by Aspergillus usamii shirousamii $U_2$ were studied and the results are as follows. 1) The production of organic acid and saccharifying amylase was stimulated by using optimum amounts of nitrofurazone and $AF_2$ among several antimicrobial agents. 2) Wheat flour medium containing 50% volumes of 10 ppm $AF_2$ solution gave the maximum yield of organic acid. 3) Wheat bran medium containing 100% volumes of $100{\sim}500ppm$ nitrofurazone solution gave the maximum yield of saccharifying amylase.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.65-68
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• 2000

To obtain quality germinated brown rices containing high levels of ${\gamma}-amonobutyric\;acid$(GABA), chitosan was appliec during the germination of brown rices. The GABA contents of germinated brown rices (1,035 umole/g fresh weight) with 100 ppm chitosan solution for 72 hr were higher than those of ungerminated brown rices (136 nmole/g fresh weight) and brown rices germinated with water (771 nmole/g fresh weight) or with lactic acid (728 nmole/g fresh weight). In addition to the enhancement of GABA, germination in the chitosan solution increased alanine and decreased glutamic acid, aspartic acid and serine in the brown rices. The activity of glutamate decarboxylase was also enhanced by the treatment of chitosan. Furthermore, the germination with chitosan reduced fungi contamination markedly compared with water germination or lactic acid germination. These results suggest that quality germinated brown rices containing high levels of GABA can be obtained by chitosan application.

• Journal of dental hygiene science
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• v.11 no.5
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• pp.411-416
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• 2011

Streptococcus mutans (S. mutans) is the major causative bacteria in dental caries. Xylitol is effective anticarious natural sugar substitute by inhibiting the virulence of S. mutans. However, long-term xylitol consumption leads to the emergence of the xylitol-resistant (XR) strains which means xylitol is no more inhibited their growth. We therefore confirmed the general characteristics and the virulence factors of the xylitol-sensitive (XS) and XR S. mutans for different concentrations of xylitol. S. mutans KCTC 3065 was maintained in TYE medium containing 0.4% glucose with 1% xylitol during 30 days at $37^{\circ}C$, 10% $CO_2$ to form XR strain. The strains were transferred to new medium every 24 hr and the same procedures without xylitol were repeated for the formation of XS S. mutans. Both XS and XR were cultured in different concentrations of xylitol (0%, 0.1% and 1%) then, cell growth, acid production and mRNA expression of gtf genes were analyzed. Xylitol reduced the cell growth of XS S. mutans in dose-dependent manner, but not reduced that of XR. Xylitol inhibited acid production of XS in dose-dependent manner, but not inhibited that of XR. Xylitol reduced the gtfB and gtfD mRNA expression of XS S. mutans which genes synthesized soluble and insoluble extracellular polysaccharides, but not reduced that of XR. These results indicate that the virulence of XR S. mutans is different characters of XS strains, which suggests XR strains may have different cariogenicity of XS strains. Further study is needed to explain the mechanism related to extracellular polysaccharide in the XR strains.

• Analytical Science and Technology
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• v.13 no.5
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• pp.659-665
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• 2000

The changes in $UV_{254}$ and concentrations of $H_2O_2$ formed by ozonation of aqueous humic acid in ozone/high pH, peroxone process and in the presence of radical scavenger, $HCO_3{^-}$ were investigated. This study confirmed that the formation of $H_2O_2$ by ozonation may undergo different reaction pathways compared to those of $UV_{254}$ reduction in the degradation of the humic acid. The concentration of $H_2O_2$ produced by ozonation was found to be increased with decreasing pH of the sample solution due to the higher stability of ozone molecules at acidic conditions. On the while, $UV_{254}$ reduction was found to be higher at alkaline conditions or larger amount of $H_2O_2$ additions as a radical promoter in which the producing of ${\cdot}OH$, ${\cdot}HO_2$ radicals can be more favorable. From the results, it has been suggested that the formation of $H_2O_2$ by ozonation depends mainly on the direct reactions of ozone with humic acid molecules, while $UV_{254}$ reduction is affected by both the indirect reactions of the radicals and direct reactions of ozone with humic acid.