• Journal of Life Science
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• v.12 no.6
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• pp.812-820
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• 2002

In order to understand stress response of Leuconostoc mesenteroides against lactic acid, a new Leuconostoc sp. which has acid tolerance was isolated from various Kimchi samples. And it identified as Leuconostoc mesenteroides LM3 by comparing its fatty acid composition with reference strain. Its growth pattern was investigated by adding a given concentration of lactic acid at the lag phase to the stationary phase. In the DeMan, Rogosa, Sharpe (MRS) media containing over 0.4% (final v/v) lactic acid, this strain slowed slowly After exposure of the stationary phase cells to 4% of lactic acid for 60 min, this strain could survive, whereas a reference strain, Leuconostoc mesenteroides KCTC3505, showed no survival. And changes of trehalose concentration, the activity of trehalase and ATPase in the growth of Leuconostoc mesenteroides LM3 after addition of 0.6% (final v/v) lactic acid were investigated : After exposure to lartic acid, trehalose concentration in this strain was increased in comparison with no treatment, but its trehalase activity was not changed. And its ATPase activity was constant, and intracellular pH was almost constant. This result meant Leuconostoc mesenteroides LM3 should have a tolerance against lactic acid. It remains to further study the mechanism of this acid tolerance.

• Microbiology and Biotechnology Letters
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• v.28 no.2
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• pp.63-70
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• 2000

To determine an increased acid tolerance of an adipic acid-resistant mutant Leuconostoc mesenteroides(ANaM100) developed for use as a Kimchi starter, proton permeability of cytoplasm, activities of H+-ATPase, Mg++ release and fatty acid composition of cytoplasmic membranes of strain ANaM100 were studied and compared with those of its wild type (LMw). The value of protons permeability of LMw after an acid shock at pH 5.0 was 5.4 min., while the value of ANaM100 cells was 8.4 min. at the same pH. The pH of maximal specific activ-ities of ATPase originated from the LMw and ANaM100 were 0.87 unit/mg protein at pH 6.0 and 0.92 unit/mg pro-tein at pH 5.5, respectively. The release of magnesium ion from ANaM100 was observed about 12.8% at pH 4 after 2 hours, while the wild strains of LMw released Mg++ about 27.6% under the same conditions. The content of C19:0,cyclo and C18:1 in a membrane fatty acid of ANaM100 was higher and lower, respectively than that of LMw. These results indicated that acid tolerance of adipic acid-resistant strain, ANaM100 was significantly improved in comparison with that of its wild type, LMw. In addition, the strain ANaM100 was adipic resistance based on the result of growth of the strain in comparison with that of strain LMw in a broth containing adipic acid.

• Journal of Microbiology and Biotechnology
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• v.30 no.5
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• pp.739-748
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• 2020

In this study, a method of heat adaptation was implemented in an attempt to increase the upper thermal threshold of two Streptococcus thermophilus found in South Korea and identified the alterations in membrane fatty acid composition to adaptive response to heat. In order to develop heat tolerant lactic acid bacteria, heat treatment was continuously applied to bacteria by increasing temperature from 60℃ until the point that no surviving cell was detected. Our results indicated significant increase in heat tolerance of heat-adapted strains compared to the wild type (WT) strains. In particular, the survival ratio of basically low heat-tolerant strain increased even more. In addition, the strains with improved heat tolerance acquired cross protection, which improved their survival ratio in acid, bile salts and osmotic conditions. A relation between heat tolerance and membrane fatty acid composition was identified. As a result of heat adaptation, the ratio of unsaturated to saturated fatty acids (UFA/SFA) and C18:1 relative concentration were decreased. C6:0 in only heat-adapted strains and C22:0 in only the naturally high heat tolerant strain were detected. These results support the hypothesis, that the consequent increase of SFA ratio is a cellular response to environmental stresses such as high temperatures, and it is able to protect the cells from acid, bile salts and osmotic conditions via cross protection. This study demonstrated that the increase in heat tolerance can be utilized as a mean to improve bacterial tolerance against various environmental stresses.

• The Plant Pathology Journal
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• v.36 no.1
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• pp.1-10
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• 2020

Since salicylic acid (SA) was discovered as an elicitor of tobacco plants inducing the resistance against Tobacco mosaic virus (TMV) in 1979, increasing reports suggest that SA indeed is a key plant hormone regulating plant immunity. In addition, recent studies indicate that SA can regulate many different responses, such as tolerance to abiotic stress, plant growth and development, and soil microbiome. In this review, we focused on the recent findings on SA's effects on resistance to biotic stresses in different plant-pathogen systems, tolerance to different abiotic stresses in different plants, plant growth and development, and soil microbiome. This allows us to discuss about the safe and practical use of SA as a plant defense activator and growth regulator. Crosstalk of SA with different plant hormones, such as abscisic acid, ethylene, jasmonic acid, and auxin in different stress and developmental conditions were also discussed.

• Food Science of Animal Resources
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• v.36 no.1
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• pp.37-43
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• 2016

Cardiovascular and cerebrovascular diseases seriously harm human health, and Bifidobacterium is the most beneficial probiotic in the gastrointestinal tract of humans. This work aimed to screen cholesterol-lowering Bifidobacterium from Guizhou Xiang Pig and evaluate its tolerance to oxygen, acid, and bile. Twenty-seven aerotolerant strains with similar colony to Bifidobacterium were isolated through incubation at 37℃ in 20% (v/v) CO₂-80% (v/v) atmospheric air by using Mupirocin lithium modified MRS agar medium, modified PTYG with added CaCO₃, and modified PTYG supplemented with X-gal. Ten strains with cholesterol-lowering rates above 20% (w/w) were used for further screening. The selected strains’ tolerance to acid and bile was then determined. A combination of colony and cell morphology, physiological, and biochemical experiments, as well as 16S rRNA gene-sequence analysis, was performed. Results suggested that BZ25 with excellent characteristics of high cholesterol-removal rate of 36.32% (w/w), as well as tolerance to acid and bile, was identified as Bifidobacterium animalis subsp. lactis. To further evaluate Bifidobacterium BZ25’s growth characteristic and tolerance to oxygen, culture experiments were performed in liquid medium and an agar plate. Findings suggested that BZ25 grew well both in environmental 20% (v/v) CO₂-80% (v/v) atmospheric air and in 100% atmospheric air because BZ25 reached an absorbance of 1.185 at 600 nm in 100% atmospheric air. Moreover, BZ25 was aerotolerant and can grow in an agar medium under the environmental condition of 100% atmospheric air. This study can lay a preliminary foundation for the potential industrial applications of BZ25.

• Food Science of Animal Resources
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• v.32 no.4
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• pp.409-413
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• 2012

This study aimed to compare the probiotic characteristics of twelve strains of Lactobacillus acidophilus including cholesterol assimilation and conjugated linoleic acid (CLA) production. Cholesterol assimilation exhibited some variation among L. acidophilus strains, which could be classified into three groups based on their assimilation levels (p<0.05). The high cholesterol assimilation group exhibited a significantly higher tolerance to 0.3 and 0.5% bile acid than the low cholesterol assimilation group (p<0.05). Cholesterol assimilation showed positive correlation with 0.5% bile tolerance, and a negative correlation with acid tolerance (p<0.01). Glycocholate deconjugation activity showed no relationship with cholesterol assimilation, whereas taurocholate deconjugation activity was shown to have negative correlation with cholesterol assimilation (p<0.05). CLA production by L. acidophilus strains exhibited a wide variation, ranging from 2.69 to 5.04 mg/g fat. CLA production of L. acidophilus GP1B was the highest among the tested strains, but there was no evidence for differences in CLA production in strain specificity. Based on these results, the cholesterol assimilation of L. acidophilus strains may not be related to deconjugation activity, but may in-fact be attributed to their bile-tolerance.

• Korean Journal of Microbiology
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• v.37 no.3
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• pp.228-233
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• 2001

The acid tolerance response (ATR) of log-phase Salmouella enterica seroyar Typhimurium is induced by acid adaptation below pH4.5 and will protect cells against more severe acid. Two distinctive ATR systems in thisorganism are a log-phase and stationary-phase ATR in which acid adaptations trigger the synthesis of acid shockproteins (ASPs). We found that log-phase ATR system was strongly affected by environmental factor, low tem-perature, $25^{\circ}C$. Exposure to low temperature and mild acid has been shown to increase acid survival dra-matically, and this survival rate was showed higher than $37^{\circ}C$. Especially unadapted cells at $25^{\circ}C$ presented tenthousand folds survival increasing when compared with cells at $37^{\circ}C$. The degree of acid tolerance of rpoSwhich is blown to be required for acid tolerance more increase than $37^{\circ}C$. Even though AIR pattern of rpoSbetween unadapted and adapted was showed similar at pH 3.1, rpoS-dependent ATR system also has beendetected in low temperature because rpoSAp prevents sustained acid survival at $25^{\circ}C$. Therefore the resultssuggest low temperature ATR system requires rpoS-dependent and -independent both. To investigate the basisfor low temperature related ATR system, gene that was participated for low temperature acid tolerance (lat) wasscreened in virulent S. enterica serovar Typhimurium UKl Using the technique of P22- MudJ (Km, lacZ)-directed lacZ operon fusion, LF452 latA‥‥MudJ was isolated. The latA‥‥MudJ of S. enterica Typhimurium pre-vented low temperature acid tolerance response. Therefore latA is considered one of the important genes for acidadaptation.

• Proceedings of the Botanical Society of Korea Conference
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• 1999.07a
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• pp.75-78
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• 1999

To obtain direct evidence for thed involvement of C-AB13, a carrot (Daucus carota L.) homolog of VPI/Ab13, seed-specific transcription factor, in the acquisition of desiccation tolerance carrot non-embryogenic cells (NC) in which the C-AB13 gene was expressed ectopically was prepared. Non-transgenic NC, in which expression of C-AB13 was not detected, did not exhibit desiccation tolerance even after treatment with abscisic acid (ABA). In transgenic NC that expressed C-AB13, embryo-specific ABA-inducible genes (ECP genes) were expressed upon ABA-treatment. Furthermore, the transgenic NC became desiccation-tolerant upon ABA-treatment, but not tolerate desiccation without ABA-treatment. These results provide direct evidence for the involvement of C-AB13 in the ABA-induced acquisition of desiccation tolerance.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.513-518
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• 1995

To evaluate bile salt-tolerance of lactic acid bacteria (LAB, Lactobacillus acidophilus ATCC 4356, Lactobacillus casei IFO 3533, Streptococcus thermnophilus KCTC 2185, Lactobacillus lactis ATCC 4797, and Lactobacillus bulgaricus ATCC 11842), We investigated the survivals, acid production and $\beta $-galactosidase activity of LAB under anaerobic broth system. Cellular permeability of LAB and their cellular retention of $\beta $-galactosidase were also examined in the same system. Although the growth of LAB was slightly suppressed by 0.3% bile salt, they showed normal growth curve. Streptococcus thermophilus KCTC 2185 was significantly more resistant to bile salt than the others. The $\beta $-galactosidase activity from Streptococcus thermophilus KCTC 2185 and Lactobacillus bulgaricus ATCC 11842 and their cellular retention of $\beta $-galactosidase decreased by 0.3% bile salt. The cellular permeability of LAB in the presence of bile salt increased significantly.

• Food Science of Animal Resources
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• v.33 no.1
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• pp.75-82
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• 2013

This study aimed to isolate lactic acid bacteria (LAB) from Kimchi and to identify suitable probiotic strain for application in fermented dairy product as a commercial starter culture. A total of 106 (LAB) strains were isolated from Kimchi collected from different regions in Korea and their phenotypic characteristics were assayed. Four isolates from MRS agar plates were selected and designated as DKL109, DKL119, DKL121 and DKL128. They were identified first by API 50 CHL kit and then 16S rRNA gene sequencing. DKL121 and DKL128 were identified as Lactobacillus paracasei and Lactobacillus casei, respectively. Other two isolates (DKL109 and DKL119) were identified as Lactobacillus plantarum. To estimate their applicability in dairy products, the characteristics including acid and bile tolerance, cold shock induced cryotolerance and enzymatic activities were determined. There was wide variation in ability of strains to acid tolerance, but no significant differences in bile tolerance, cold shock induced cryotolerance within selected strains. DKL119 and DKL121 showed the highest resistance to acid and bile and the highest ${\beta}$-galactosidase activity, respectively. When these two strains were used for yogurt preparation as a single starter culture, their viable cell counts reached to $1.0{\times}10^9CFU/mL$. Lactobacillus plantarum DKL119 showed faster acid development than commercial starter culture. Also storage trials at $10^{\circ}C$ showed that the viability of these strains was retained over 15 d. With these results, it was indicated that probiotics isolated from Kimchi can be used in yogurt manufacturing as a starter culture.