• Korean Journal of Food Science and Technology
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• v.28 no.1
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• pp.117-121
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• 1996

In order to find the reason for souring of Hansan sogokju (Korean traditional rice wine), microbial distribution, pH change and organic acids were analysed. Besides 161 mM of lactic acid as a major organic acid, small amount of acetic acid, malic acid, propionic acid were found in sogokju. Four different microbial strains were identified from the sogokju. These are two strains of Lactobacillus spp., Bacillus sp. and yeast. The pH of sogokju was changed from 4.01 to 3.29 during 18 days storage at $30^{\circ}C$. Amount of total acidity increased from 9 to 34.86 at the same condition. Notable change in the soured sogokju was an increase of the lactic acid (from 161 mM to 192 mM). So, we could assume that it was soured by an additional production of lactic acid by lactic acid bacteria during storage. The shelf life of sogokju was 41 days below $15^{\circ}C$ degree because this temperature was hard condition for the growth of Lactobacillus spp., causative bacteria responsible for additional lactic acid production.

• Korean Journal of Food Science and Technology
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• v.33 no.5
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• pp.589-595
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• 2001

Effect of anti-microbial agents, such as alcohol, garlic, chitosan, K-sorbate, or mustard, or pasteurization on the quality of traditional kochujang was investigated during storage at $30^{\circ}C$ for 24 weeks. Water activities of kochujang decreased after 12 weeks of storage. Consistency increased during storage and highest consistency of kochujang was obtained by the addition of mustard or garlic. Hunter a- and b-values decreased linearly as storage time passed. The degree of increase in total color difference$({\Delta}E)$ of alcohol added group was the highest among the tested anti-microbial agents. Gas was rapidly produced in the control and chitosan added group of kochujang. Capsanthin content decreased more rapidly in the group of alcohol, garlic or mustard added kochujang than the other group. Viable cell counts of yeast and aerobic bacteria in kochujang increased up to 12 weeks of storage, and then decreased slowly. The number of yeast was low in K-sorbate or alcohol added group. Activity of ${\alpha}-amylase$ decreased during storage, but that of ${\beta}-amylase$ increased in alcohol, garlic, K-sorbate added or pasteurized kochujang. Protease activities did not show any remarkable differences in the groups of tested during storage.

• Food Science and Preservation
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• v.14 no.2
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• pp.194-200
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• 2007

In order to enhance the functionality and storage period of traditional fermented foods, the strain CH-14, which To enhance the quality of traditional fermented foods, and to lengthen acceptable storage periods, a bacterial strain, CH-14, showing potent enzyme activities and antibacterial capabilities, was isolated and characterize4 The bacterium wn Gram-positive, catalase-positive, oxidase-negative, formed endospores, expressed flagella, was rod-shaped, and had dimensions of 0.5 0.7m and 3.5 4.2m. The bacterium CH-14 was identified as Bacillus subtilis using Bergey's Manual of Systematic Bacteriology, Bergey's Manual of Determinative Bacteriology, and an API 50 CHL Carbohydrate Test Kit. An optimum growth medium contained 2% (w/v) cellobiose as a carbon source, a mixture of 0.5% (w/v) yeast extract and 0.5% (w/v) peptone as nitrogen sources, and 0.05% (w/v) $MgSO_4{\cdot}7H_2O$. The optimal culture temperature and the optimal initial pH were in the ranges of 30 $45^{\circ}C$ and 4.5 10.0, respectively. Maximum production of the antibacterial substance occurred after 24h of culture. The minimum inhibitory concentrations of the antibacterial substance were 5mg bacterial dry weight/mL against E. coli and P. mirabilis, and 10 mg/mL against S. aureus, S. enteritidis and V. parahaemolyticus.

• Journal of Ecology and Environment
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• v.48 no.1
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• pp.17-23
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• 2024

Background: Honey bees play a crucial role in pollination and ecological balance. Apis mellifera L. colonies, especially those located in specific geographic regions, such as the palm garden in Eastern Thailand, are susceptible to potential threats from microbial contaminants. Understanding and detecting microbial organisms in these beehives is essential for the preservation of bee health, honey production, and the broader ecosystem. However, the problem of microbial infection and antibiotic-resistant bacteria is more severe and continuously increasing, resulting in a health, economic, and social crisis. The purpose of this study is to determine the prevalence of microorganisms in A. mellifera beehives in palm gardens in Rayong province, Eastern Thailand. Results: Ten swabs in transport media were swabbed and obtained from different parts of each beehive (1 swab per beehive), for a total of 10 hives. Traditional microbial culture-based methods, biochemical tests, and antimicrobial susceptibility (disc-diffusion) tests were used to detect microbial organisms and antibiotic resistance in bacteria. The swab tests from nine beehives resulted in the detection of Gram-positive bacteria (63.64%), Gram-negative bacteria (27.27%), and fungi/yeast (9.09%). These microorganisms are classified as a group of coagulase-negative Staphylococcus spp. and made up 40.91% of the bacteria discovered. Other bacteria found were Coryneform bacteria (13.64%), Pantoea spp. (13.64%), Bacillus spp. (9.09%), yeast (9.09%), glucose non-fermentative Gram-negative bacilli (9.09%), and Pseudomonas spp. (4.55%). However, due to the traditional culture-based and 0biochemical tests usually used to identify the microbial organisms in clinical specimens and the limitation of identifying some environmental microbial species, the results of the antimicrobial susceptibility test cannot reveal if the organism is resistant or susceptible to the drug. Nevertheless, drug-sensitive inhibition zones were formed with each antibiotic agent. Conclusions: Overall, the study supports prevention, healthcare, and public health systems. The contamination of microorganisms in the beehives may affect the quality of honey and other bee products or even the health of the beekeeper. To avoid this kind of contamination, it is therefore necessary to wear personal protective equipment while harvesting honey and other bee products.

• Korean Journal of Food Science and Technology
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• v.41 no.3
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• pp.296-301
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• 2009

In order to investigate the effect of different yeasts (La Parisienne (LP), Y18-2, Y54-3, Y90-2, Y90-9 and Y272-7) from nuruks on the quality of Glutinous rice wines, physicochemical properties and volatile flavor components were evaluated. Glutinous rice wines prepared with different yeasts were analyzed for ethanol, pH, total acid, amino acid, soluble solid, coloring degree, UV absorbance, reducing sugar, organic acid, free sugar and volatile compounds. After fermentation for 17 days, the ethanol contents ranged from 13.40 to 14.50%, while the total acid levels were from 0.33 to 0.44%. The amino acid contents in six samples ranged from 0.13 to 0.18%, while soluble solid contents ranged from 12.1 to $14.7^{\circ}Bx$. The glutinous rice wine prepared with LP showed the highest level of coloring degree, soluble solid and reducing sugar among six samples. Organic acid contents of the glutinous rice wine prepared with LP had the highest levels of lactic acid and acetic acid, while the glutinous rice wine prepared with Y90-9 had the highest level of succinic acid. In all glutinous rice wines tested, the most abundant free sugars were glucose followed by maltose. Volatile flavor components in the glutinous rice wines were identified by using GC-MSD. Nineteen esters, ten alcohols, eight acids, one aldehyde and one miscellaneous compound were identified in the glutinous rice wines. Using relative peak area, it was found that other than ethyl alcohol, hexadecanoic acid ethyl ester was the major component, predominantly found in the range of 2.73-10.41%. Phenylethyl alcohol, isoamyl alcohol, ethyl oleate, ethyl linoleate and tetradecanoic acid ethyl ester were some of the major volatile components present through the fermentation, respectively. Overall, it was shown that different yeast strains from nuruks greatly affected chemical and volatile characteristics of the glutinous rice wines.

• Food Science and Preservation
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• v.17 no.3
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• pp.410-417
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• 2010

Several extracellular protease-producing bacteria were isolated from Chungkookjang, a traditional Korean food of fermented soybeans, on skim milk agar plates. Among these bacteria, strain D14 exhibited the highest production (15.2 U/mL) and specific activity (40.0 U/mg protein) of extracellular protease activity as assessed on growth in a protease induction medium composed of 1% (w/v) soluble starch, 1.5% (w/v) skim milk, 0.5% (w/v) yeast extract, and 2% (w/v) NaCl. The bacterium was identified as Bacillus subtilis based on morphological and physiological characteristics and 16S rDNA sequence. A BLAST search of 16S rDNA sequences revealed that the isolate was most closely related to Bacillus subtilis subsp. subtilis strain NCIB 3610. The 16S rDNA sequence homology was 99.9%. Our isolate produced the highest level of protease when grown in a protease induction medium containing 1% (w/v) sorbitol and 0.5% (w/v) yeast extract. Fructose and glucose reduced enzyme production to 12.7% and 35.9%, respectively, of the level seen when the strain was grown in medium containing soluble starch. Soytone also reduced enzyme production to 61.4% of the level noted when the strain was grown in medium containing yeast extract.

• Journal of Microbiology and Biotechnology
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• v.27 no.10
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• pp.1736-1743
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• 2017

Sourdough is made by fermentation of dough by lactic acid bacteria (LAB) and yeast to improve bread properties like volume, flavor, and texture. A Korean traditional sourdough was made by fermenting rice flour with rice wine (makgeolli) and used to make sponge-like bread (jeung-pyun). The aim of this study was to investigate the microbial diversity of makgeolli products and their influence on the organoleptic quality of jeung-pyun. Three commercial makgeolli were tested for jeung-pyun production, with each product exhibiting varied dough swelling rates and organoleptic qualities, and among them, J-product was ranked highest in texture and taste. Microbial analysis of the three makgeolli also showed a big difference in their population and diversity. J-product had the highest LAB and yeast counts, and the predominant species were Lactobacillus casei, Lactobacillus brevis, Leuconostoc pseudomenteroides, and Saccharomyces cerevisiae. Using J-product, sourdough was fermented at $25^{\circ}C$, $30^{\circ}C$, and $35^{\circ}C$, and the microbial growth in and textural properties of jeung-pyun were examined by instrumental and sensory tests. At high temperature ($35^{\circ}C$), the rates of dough swelling and acidification were fast due to rapid microbial growth mainly caused by LAB, resulting in a short leavening time and soft and sour jeung-pyun. Sensory tests showed consumer preference for the soft and mild-sour jeung-pyun. This study shows that LAB in makgeolli play key roles in production of jeung-pyun, influencing the textural and sensory properties. For the production of high-quality jeung-pyun, development of LAB starters with high gas productivity and low acidity and establishment of an optimal fermentation procedure for rice dough are necessary.

• Journal of Microbiology and Biotechnology
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• v.30 no.5
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• pp.785-792
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• 2020

ʟ-Theanine, found in green tea leaves has been shown to positively affect immunity and relaxation in humans. There have been many attempts to produce ʟ-theanine through enzymatic synthesis to overcome the limitations of traditional methods. Among the many genes coding for enzymes in the ʟ-theanine biosynthesis, glutamylmethylamide synthetase (GMAS) exhibits the greatest possibility of producing large amounts of production. Thus, GMAS from Methylovorus mays No. 9 was overexpressed in several strains including vectors with different copy numbers. BW25113(DE3) cells containing the pET24ma::gmas was selected for strains. The optimal temperature, pH, and metal ion concentration were 50℃, 7, and 5 mM MnCl₂, respectively. Additionally, ATP was found to be an important factor for producing high concentration of ʟ-theanine so several strains were tested during the reaction for ATP regeneration. Baker's yeast was found to decrease the demand for ATP most effectively. Addition of potassium phosphate source was demonstrated by producing 4-fold higher ʟ-theanine. To enhance the conversion yield, GMAS was additionally overexpressed in the system. A maximum of 198 mM ʟ-theanine was produced with 16.5 mmol/l/h productivity. The whole-cell reaction involving GMAS has greatest potential for scale-up production of ʟ-theanine.

• Journal of Mushroom
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• v.11 no.4
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• pp.194-200
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• 2013

Polyporus umbellatus (Syn. Grifola umbellata) is a sclerotium forming mushroom belongs to family Polyporaceae of Polyphorales, Basidiomycota. The sclerotia of P. umbellatus have long been used for traditional medicines in China, Korea and Japan. This study was initiated to obtain the basic data for artificial sclerotial production of P. umbellatus. Here, we investigated the favorable conditions for mycelial growth of P. umbellatus and its symbiotic fungus Armillaria mellea. We also evaluate the favorable carbon and nitrogen sources for sclerotial formation in dual culture between P. umbellatus and A. mellea. The favorable conditions for mycelial growth of P. umbellatus were $20^{\circ}C$ and pH 4, while optimal conditions for mycelial growth of A. mellea were $25^{\circ}C$ and pH 6. The carbon sources for optimal mycelial growth of P. umbellatus were fructose and glucose, while carbon sources for favorable mycelial growth of A. mellea were also fructose and glucose. The nitrogen sources for favorable mycelial growth P. umbellatus were peptone and yeast extract, while optimal mycelial growth of A. mellea were obtained in peptone and yeast extract. When P. umbellatus and A. mellea were dual cultured on carbon sources, sclerotia were induced on basal media supplemented with glucose, fructose and maltose at pH 4~6, while nitrogen sources inducing sclerotia were basal media supplemented with peptone and yeast extract for 60 days at $20^{\circ}C$ under dark condition.

• Korean Journal of Food Science and Technology
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• v.40 no.5
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• pp.558-561
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• 2008

Culture broth of Bacillus subtilis Y3-7 in tryptic soy broth (TSB) isolated from Korean traditional fermented food was evaluated for the inhibition of $\alpha$-glucosidase. The results of in vitro studies using the yeast $\alpha$-glucosidase demonstrated that the culture broth exerted inhibitory effects on $\alpha$-glucosidase with $IC_{50}$ value of 1.62 mg/mL, and functioned as a competitive inhibitor. Furthermore, the culture broth of B. subtilis Y3-7 significantly improved glucose tolerance in normal and streptozotocin-induced diabetic mice. The blood glucose levels in the mice receiving sucrose supplementation in the culture broth (1 g/kg, 2 g/kg) were measured at 48.7%, which corresponded to 22.2% of the levels measured in the control mice. These results indicated that the culture broth of B. subtilis Y3-7 in TSB might be considered as a useful compound for the preparation of functional foods for diabetic patients.