• Journal of Microbiology and Biotechnology
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• v.23 no.10
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• pp.1428-1433
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• 2013

Jeotgal fermentation is dependent upon a diverse microbial community, although a detailed understanding of its microbial composition is limited to a relatively small number of jeotgal. Pyrosequencing-based bacterial community analysis was performed in fermented squid, ojingeo jeotgal. Leuconostoc was identified as the predominant bacterial genus, with Bacillus and Staphylococcus also accounting for a large proportion of the bacterial community. Phylogenetic analysis with 16S rRNA genes of Leuconostoc type species indicated that L. citreum- and L. holzapfelii-like strains could be the major Leuconostoc strains in jeotgal. High concentrations of NaCl were thought to be an important factor determining the makeup of the bacterial community in the fermented squid; however, a genomic survey with osmotic stress-related genes suggests the existence of more complex factors selecting the dominant bacterial species in fermented squid.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.4
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• pp.603-615
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• 2008

Dietary fiber is an inevitable component in pig diets. In non-ruminants, it may influence many physiological processes in the gastrointestinal tract (GIT) such as transit time as well as nutrient digestion and absorption. Moreover, dietary fiber is also the main substrate of intestinal bacteria. The bacterial community structure is largely susceptible to changes in the fiber content of a pig's diet. Indeed, bacterial composition in the lower GIT will adapt to the supply of high levels of dietary fiber by increased growth of bacteria with cellulolytic, pectinolytic and hemicellulolytic activities such as Ruminococcus spp., Bacteroides spp. and Clostridium spp. Furthermore, there is growing evidence for growth promotion of beneficial bacteria, such as lactobacilli and bifidobacteria, by certain types of dietary fiber in the small intestine of pigs. Studies in rats have shown that both phosphorus (P) and calcium (Ca) play an important role in the fermentative activity and growth of the intestinal microbiota. This can be attributed to the significance of P for the bacterial cell metabolism and to the buffering functions of Ca-phosphate in intestinal digesta. Moreover, under P deficient conditions, ruminal NDF degradation as well as VFA and bacterial ATP production are reduced. Similar studies in pigs are scarce but there is some evidence that dietary fiber may influence the ileal and fecal P digestibility as well as P disappearance in the large intestine, probably due to microbial P requirement for fermentation. On the other hand, fermentation of dietary fiber may improve the availability of minerals such as P and Ca which can be subsequently absorbed and/or utilized by the microbiota of the pig's large intestine.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.10a
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• pp.8-8
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• 2019

The stringent response (SR) is characterized as a bacterial defense mechanism in response to various growth-inhibiting stresses. It is activated by accumulation of a small nucleotide regulator, (p)ppGpp, and induces global changes in bacterial transcription and translation. Recent work from our group has shown that (p)ppGpp plays a critical role in virulence and survival in Vibrio cholerae. The genes, relA and relV, are involved in the production of (p)ppGpp, while the spoT gene encodes an enzyme that hydrolyzes it in V. cholerae. A mutant strain defective in (p)ppGpp production (i.e. ${\Delta}relA{\Delta}relV{\Delta}spoT$ mutant) lost the ability to produce cholera toxin (CT) and lost their viability due to uncontrolled production of organic acids, when grown with extra glucose. In contrast, the ${\Delta}relA{\Delta}spoT$ mutant, a (p)ppGpp overproducer strain, produced enhanced level of CT and exhibited better growth in glucose supplemented media via glucose metabolic switch from organic fermentation to acetoin, a neutral fermentation end product, fermentation. These findings indicates that (p)ppGpp, in addition to its well-known role as a SR mediator, positively regulates CT production and maintenance of growth fitness in V. cholerae. This implicates SR as a promising drug target, inhibition of which may possibly downregulate V. cholerae virulence and survival fitness. Therefore, we screened a chemical library and identified a compound that induces medium acidification (termed iMAC) and thereby loss of wild type V. cholerae viability under glucose-rich conditions. Further, we present a potential mechanism by which the compound inhibits (p)ppGpp accumulation. Together, these results indicate that iMAC treatment causes V. cholerae cells to produce significantly less (p)ppGpp, an important regulator of the bacterial virulence and survival response, and further suggesting that it has a therapeutic potential to be developed as a novel antibacterial agent against cholera.

• Proceedings of the Microbiological Society of Korea Conference
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• 1998.04a
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• pp.46.1-46.1
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• 1998

• Preventive Nutrition and Food Science
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• v.7 no.1
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• pp.37-42
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• 2002

Factors affecting the production of bacterial cellulose and organic acids in Kombucha fermentation were investigated. Kombucha was obtained by the fermentation (for 12 days at 3$0^{\circ}C$) of the green/black tea extract, supplemented with 10% white sugar, using an Oriental tea fungus as starter. Hitgher initial pH increased acid production with decreased cellulose production. With a cellulose pellicle or tea fungus broth as a starter, a 1~3 mm thick cellulose layer developed as a top layer every four days, and was removed subsequently while continuing fermentation. Addition of 30 mL tea fungus broth (13%, v/v) in Kombucha fermentation resulted in maximum production of a cellulose pellicle, indicating weak acid production. Yield of cellulose production at an early stage of fermentation was also higher when Kombucha was inoculated with a cellulose pellicle. In fact, addition of 1% (v/v) alcoholic beverage in the Kombucha fermentation activated the cellulose production, coupled with four times higher acid production.

• Microbiology and Biotechnology Letters
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• v.20 no.1
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• pp.102-109
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• 1992

The microfloral changes of lactic acid bacteria during Kimchi fermentation at 5, 20 and $30^{\circ}C$ were compared by using various selective media, and the lactic acid bacterial strains were isolated and identified. The patterns of microfloral changes in each lactic acid bacterial group, leuconostoc, lactobacilli, streptococci and pediococci, were similar at different fermentation temperature, and the changes were accelerated by increased temperature. Among them, leuconostoc and lactobacilli showed high population, and at low temperature the number of leuconostoc were higher than at high temperature. Leuconostoc and streptococci were increased in number from the beginning, but they rapidly decreased after the optimum ripening period. Pediococci increased their number after streptococci, but they were rapidly decreased later. Lactobacilli were highly distributed throughout the whole fermentation period. However, they were slightly declined as the acidity increased. Those strains of leuconostoc, streptococci, pediococci and lactobacilli were identified as Luuconostoc mesenteroida subsp. musenteroides, Streptococcus fuecalzs, S, faeciurn, Pediococcus pentosaceus, Lactobacillus plarttarum, L. sake and L. brevis. Among lactobacilli, Id. sake and L. brmk, and L. plantarum were isolated mainly at the beginning and around the overripening period of fermentation, respectively.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.5
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• pp.665-674
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• 2019

Objective: In tropical regions, as in temperate regions where seasonality of forage production occurs, well-preserved forage is necessary for animal production during periods of forage shortage. However, the unique climate conditions (hot and humid) and forage characteristics (high moisture content and low soluble carbohydrate) in the tropics make forage preservation more difficult. The current study used natural ensiling of tropical forage as a model to evaluate silage characteristics under different temperatures ($28^{\circ}C$ and $40^{\circ}C$). Methods: Four tropical forages (king grass, paspalum, white popinac, and stylo) were ensiled under different temperatures ($28^{\circ}C$ and $40^{\circ}C$). After ensiling for 30 and 60 days, samples were collected to examine the fermentation quality, chemical composition and microbial community. Results: High concentrations of acetic acid (ranging from 7.8 to 38.5 g/kg dry matter [DM]) were detected in silages of king grass, paspalum and stylo with relatively low DM (ranging from 23.9% to 30.8% fresh material [FM]) content, acetic acid production was promoted with increased temperature and prolonged ensiling. Small concentrations of organic acid (ranging from 0.3 to 3.1 g/kg DM) were detected in silage of white popinac with high DM content (50.8% FM). The microbial diversity analysis indicated that Cyanobacteria originally dominated the bacterial community for these four tropical forages and was replaced by Lactobacillus and Enterobacter after ensiling. Conclusion: The results suggested that forage silages under tropical climate conditions showed enhanced acetate fermentation, while high DM materials showed limited fermentation. Lactobacillus and Enterobacter were the most probable genera responsible for tropical silage fermentation.

• Journal of Microbiology and Biotechnology
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• v.29 no.10
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• pp.1580-1590
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• 2019

Capsaicinoids in red pepper powder are known to show anti-bacterial effects; however, their effects during kimchi fermentation are not known. This study aimed to investigate the effects of various concentrations of capsaicinoids on kimchi fermentation. Five sets of kimchi samples were prepared using 0 mg/kg (control), $98.34{\pm}5.34mg/kg$ (mild), $243.47{\pm}3.71mg/kg$ (medium), $428.63{\pm}30.78mg/kg$ (hot), and $1,320.49{\pm}28.27mg/kg$ (extreme) capsaicinoid. The characteristics of each kimchi sample, including pH, acidity, organic acid, sugars, sugar alcohol, capsaicinoid content, and microbial community were periodically investigated during fermentation. Kimchi with red pepper powder shows significantly higher acidity than control kimchi, whereas pH values were the same. Organic acid in kimchi with red pepper powder was higher than in control kimchi, probably caused by higher lactic acid bacteria (LAB) counts in kimchi samples with red pepper powder. Our results show that addition of red pepper powder decreased Leuconostoc spp. counts in the bacterial community. In particular, Lactobacillus sakei and Leuconostoc gelidum counts increased and decreased, respectively, with increasing capsaicinoid content of red pepper powder added to kimchi. Overall, the results of this study indicate that physicochemical properties and LAB such as L. sakei and L. gelidum are influenced by capsaicinoid content. However, further studies are necessary to investigate the effects of the percentage of red pepper powder in kimchi on fermentation to provide practical guidelines for producing standardized kimchi.

• Microbiology and Biotechnology Letters
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• v.22 no.5
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• pp.550-556
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• 1994

For an extension of the palatable stage in Kimchi which was limited by further lowering pH as the fermentation proceeds, the starter culture of bacteriocin-producing Enterococcus faecium DU 0267 obtained from Kimchi was added at the preparation time, and pH, bacteriocin activity, growth of lactic acid bacterial group and gas production in Kimchi were examined during the fermentation at 10, 20 and 30$\circ$C . The pH of Kimchi fell rapidly to 4.0~4.2 in the early fermentation stage, and then, has gone down very slowly throughout further fermentation. The lactic acid bacte- ria, particularly lactobacilli and leuconostoc, were remarkably slower in its growth than those in the control. Although the patterns of these change during fermentation at different temperatures were similar, these effects by the addition of starter were enhanced at 10 and 20$\circ$C. The bacteriocin activity was increased rapidly during log phase of the bacteriocin producer strain in the early fermentation stage of Kimchi and reached their maximum after fermentation at 10$\circC, for 8 days and at 20 or 30$\circ$C for 2 days. Thereafter, the activity disappeared quickly. The gas production by fermentation was also suppressed considerably, and their volume produced after fermentation at 20$\circ$C for 14 days corresponded to 60% of those of the control.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.10
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• pp.1528-1539
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• 2019

Objective: To evaluate the effects on microbial diversity and biochemical parameters of gradually increasing temperatures, from $5^{\circ}C$ to $25^{\circ}C$ on corn silage which was previously fermented at ambient or low temperature. Methods: Whole-plant corn silage was fermented in vacuum bag mini-silos at either $10^{\circ}C$ or $20^{\circ}C$ for two months and stored at $5^{\circ}C$ for two months. The mini-silos were then subjected to additional incubation from $5^{\circ}C$ to $25^{\circ}C$ in $5^{\circ}C$ increments. Bacterial and fungal diversity was assessed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) profiling and biochemical analysis from mini-silos collected at each temperature. Results: A temperature of $10^{\circ}C$ during fermentation restricted silage fermentation compared to fermentation temperature of $20^{\circ}C$. As storage temperature increased from $5^{\circ}C$ to $25^{\circ}C$, little changes occurred in silages fermented at $20^{\circ}C$, in terms of most biochemical parameters as well as bacterial and fungal populations. However, a high number of enterobacteria and yeasts (4 to $5\;log_{10}$ colony forming unit/g fresh materials) were detected at $15^{\circ}C$ and above. PCR-DGGE profile showed that Candida humilis predominated the fungi flora. For silage fermented at $10^{\circ}C$, no significant changes were observed in most silage characteristics when temperature was increased from $5^{\circ}C$ to $20^{\circ}C$. However, above $20^{\circ}C$, silage fermentation resumed as observed from the significantly increased number of lactic acid bacteria colonies, acetic acid content, and the rapid decline in pH and water-soluble carbohydrates concentration. DGGE results showed that Lactobacillus buchneri started to dominate the bacterial flora as temperature increased from $20^{\circ}C$ to $25^{\circ}C$. Conclusion: Temperature during fermentation as well as temperature during storage modulates microorganism population development and fermentation patterns. Silage fermented at $20^{\circ}C$ indicated that these silages should have lower aerobic stability at opening because of better survival of yeasts and enterobacteria.