• Journal of Microbiology and Biotechnology
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• v.11 no.6
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• pp.915-921
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• 2001

Phytase improves the bioavailability of phytate phosphorus in plant foods to humans and animals, and reduces the phosphorus pollution of animal waste. In order to express a high level of fungal phytase in Saccharomyces cerevisiae, various expression vectors were constructed with different combinations of promoters, translation enhancers, signal peptides, and terminator. Three different promoters fused to the phytase gene (phyA) from Aspergillus niger were tested: a galactokinase (GAL1) promoter, glyceraldehyde-3-phosphate dehydrogenase (GPD) promoter, and yeast hybrid ADH2-GPD promoter consisting of alcohol dehydrogenase II (ADH2) and a GPD promoter. The signal peptides of phytase, glucose oxidase (GO), and rice amylase 1A(RAmy1A) were included. Plus, the translation enhancers of the ${\Omega}$ sequence and UTR70 from the tobacco mosaic virus (TMV) and spinach, respectively, were also tested. Among the recombinant vectors, pGphyA06 containing the GPD promoter, the ${\Omega}$ sequence, RAmy1A, and GAL7 terminator expressed the highest phytase activity in a culture filtrate, which was estimated at 20 IU/ml. An intracellular localization of the expressed phytase activity in a culture filtrate, which was estimated at 20 IU/ml. An intracellular localization of the expressed phytase was also performed by inserting an endoplasmic reticulum (ER) retention signal, KDEL sequence, into the C-terminus of the phytase within the vector pHphyA-6. It appeared that the KDEL sequence directed most of the early expression of phytase into the intracellular compartment yet more than $60\%$ of the total phytase activity was still retained within the cell even after the prolonged (>3 days) incubation of the transformant. However, the intracellular enzyme activity of the transformant without a KDEL sequence was as high as that of the extracellular one, thereby strongly suggesting that the secretion of phytase in S. cerevisiae appeared to be the rate-limiting step for the expression of a large amount of extracellular recombinant phytase, when compared with other yeasts.

• Applied Biological Chemistry
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• v.51 no.4
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• pp.281-287
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• 2008

Effect of combined use of anti-microbial materials, such as alcohol, mustard and chitosan, or pasteurization on the quality of low salted kochujang was investigated during storage at $30^{\circ}C$ for 12 weeks. Activity of amylase decreased during storage, with lower activity in pasteurized kochujang than the other groups. Acidic protease activity increased during storage, but neutral protease activity decreased after 4 weeks. Viable cells of yeast increased during storage, but bacterial counts decreased gradually and did not show any remarkable difference among the test groups. Hunter a-values decreased as storage time increased, whereas L- and b-values decreased after 4 weeks and the degree of increase in total color difference (${\Delta}E$) was low in the supplementary ingredients added kochujang. The moisture contents and water activities decreased during storage with being lower in supplementary ingredients added groups. Titratable acidity of kochujang was decreased after 4 weeks of storage with the highest in combination of the supplementary ingredients added group. Oxidation-reduction potential was low in the supplementary ingredients added kochujang. Total sugar and reducing sugar contents of kochujang decreased during storage, with the highest contents in the supplementary ingredients added group. Ethanol content of kochujang increased during storage, whereas ethanol production was reduced in ethanol added one. Amino-nitrogen and ammonia-nitrogen contents decreased during storage with being lower in kochujang prepared with supplementary ingredients. Therefore, supplementary ingredients added kochujang would be effective for extending shelf-life of kochujang.

• Food Science and Preservation
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• v.23 no.4
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• pp.538-546
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• 2016

Kochujang was prepared by replacement of rice (25%, control) with pumpkin or purple sweet potato by 0. 5, 10, and 15% (total addition ratio of rice and sweet potato=25% of sample). Effects of the addition of sweet potato on physiochemical properties of fermented Kochujang were investigated. Viable cells of yeast decreased in the sweet potato-added Kochujang at the later stage of fermentation, while there was no significant difference in the number of bacteria among the test groups. As the addition ratio sweet potato increased, ${\alpha}$-amylase activity increased while protease activity decreased. Hunter L, a, and b values of Kochujang prepared with purple sweet potato were lower than those with pumpkin sweet potato. Changes in ${\Delta}E$ value was greater in Kochujang prepared with pumpkin sweet potato than that with purple sweet potato. Oxidation-reduction potential and water activity were higher in sweet potato-Kochujang than control, but reducing sugar content was higher in control. Alcohol and amino-type nitrogen contents were higher in Kochujang prepared with pumpkin sweet potato than that with purple sweet potato, but it was not significant. Overall sensory acceptability was highest in Kochujang prepared with 10% of purple sweet potato while that with 15% pumpkin sweet potato was the least preferred.

• Food Science and Preservation
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• v.17 no.2
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• pp.230-235
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• 2010

We investigated the physicochemical quality characteristics of apple juice upon sterilization using hot water, and under various storage conditions. None of sugar content, acidity, or pH differed significantly among various sterilization conditions but chromaticity was considerably reduced in sterilized juice compared with control material. The chromaticity of non-sterilized juice decreased significantly after sterilization compared with material supplemented with vitamin C (0.1%, w/v). Fungi, yeast, and aerobic bacteria were detected in juice sterilized at $65^{\circ}C$ for 10 or 20 min, but no microorganisms were observed in juice sterilized by other procedures. Vitamin C content affected sterilization temperature to a greater extent than sterilization time. When juice was stored at $4^{\circ}C$ or $37^{\circ}C$ for 3 weeks after application of different sterilization conditions, almost no change in acidity, sugar content, or pH was observed, regardless of sterilization mode or storage period. However, chromaticity decreased with longer storage. Vitamin C levels were reduced by higher sterilization temperatures. However, longer storage periods had the greatest effect on reduction of vitamin C levels, which tended toward lower values regardless of differences in sterilization and storage conditions. In sensory evaluation tests, all of taste, color, and overall preference were highest for juice sterilized at $75^{\circ}C$ for 20 min. The ASC value was low at a storage temperature of $4^{\circ}C$ and at high sterilization temperatures, and a long storage period was associated with a greater ASC value. Thus, the quality of apple juice was excellent when juice was hot water-sterilized, with additional vitamin C, at $75^{\circ}C$ for 20 min, followed by storage at $4^{\circ}C$.

• Journal of Life Science
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• v.19 no.3
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• pp.322-326
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• 2009

Glutathione is a well-known chemotherapeutic agent and a popular nutritional supplement for liver disease and oxidative stress. Our previous studies reported the suppressive effects of the glutathione-enriched Saccharomyces cerevisiae FF-8 (FF-8) strain on carbon tetrachloride- and alcohol-induced oxidative stress in rats. The purpose of the current study was to investigate the effect of the FF-8 strain on lipid peroxidation in tissues of rats with orotic acid (OA)-induced fatty liver. OA treatment showed a significant decrease in body weight gain compared to the normal diet, and simultaneous addition of FF-8 and OA had the same effect. OA treatment produced an increase in liver weight, however, this also increased with simultaneous addition of FF-8 and OA. Liver lipid peroxidation was significantly increased by OA, but was significantly decreased by FF-8 strain treatment. This same tendency was found in the kidney and heart. Concentration levels of hepatic glutathione and zinc are known to be closely associated with the antioxidant system, and OA treatment led to reductions in liver glutathione and zinc concentrations, whereas these were significantly increased by FF-8 strain treatment in OA feeding rats. These results suggest that the glutathione-enriched S. cerevisiae FF-8 strain may positively mediate orotic acid-induced oxidative stress by enhancing glutathione and zinc levels in rat livers.

• Korean Journal of Food Science and Technology
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• v.45 no.6
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• pp.727-734
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• 2013

Makgeolli mashes that were brewed using five different commercial nuruks (fermentation starters) were investigated for changes in physicochemistry, microbial diversity, and biogenic amine (BA) production. Mash A brewed with the nuruk (Gaeryang-nuruk) had the highest level of alcohol concentration and the greatest number of yeast cells, whereas mash E had the greatest number of bacterial cells. Only three biogenic amines were detected in the makgeolli mashes: tyramine, putrescine, and cadaverine. Using a PCR-DGGE technique, we observed that mash E had the highest BA production, and had the greatest number of bands on the denaturing gradient gels. We also observed that the numbers of bacterial cells correlated significantly with the putrescine and the total BA content, and that the BA content correlated significantly with the color values (L, a, b). This study shows that the quality of a makgeolli can depend on the type of nuruk. Therefore, we suggest that the quality management of makgeolli should start with the stage of nuruk manufacture.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.6
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• pp.975-982
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• 2013

In this study, we evaluated the physicochemical, microbial, and sensory characteristics of Makgeolli made with loquat fruits during fermentation. The pH values of all samples decreased after 3 days of fermentation, with a final pH ranging from 3.91 to 4.05. Total acidity increased (from 0.71 to 0.76%) from the addition of loquat fruits after 15 days of fermentation. Amino acid content increased (from 0.13 to 0.22%) with fermentation time after 15 days of fermentation. Total sugar and reducing sugar content decreased with fermentation, but was significantly higher with the addition of loquat fruit. The alcohol content of the loquat-added groups was also higher compared to the control group after 15 days of fermentation. The microbial and yeast count of all samples increased to its maximum after 3 days and then decreased after 5 days of fermentation. The sensory score of Makgeolli made with 3% loquat fruit showed higher values than other samples. The results of this study suggest that loquat effectively serves as a natural additive for improving the sensory qualities of Makgeolli and potentially other foods.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.6
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• pp.847-854
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• 2003

In general cooked rice would be used as a major raw material for making Takju. In this case quality, taste and storage time of Takju were not fully satisfied. Fermentation conditions for Takiu mash were examined by using the germed brown rice in this study. In case of the germed brown rice on 2nd stage mash, alcohol was slowly generated in comparison with the cooked rice. Reducing sugar was slowly produced and the amount of reducing sugar was low. The sugar content was created at a uniform rate. The pH was shown to be higher in mash of the germed brown rice than that of the cooked rice. Acidity change showed a similar inclination to pH change. The degree of yeast growth on the mash of the germed brown rice was revealed to be slightly lower than that of the cooked rice. Temperature of mash was kept to be constant after 3 days from fermentation. Fusel oil produced from the mash of the germed brown rice was less gernerated in comparison with the cooked rice. Amount of amino acid in case of the germed brown rice was indicated to be higher. Takju made with the germed brown rice was shown to be 1.3 times in overall taste, 1.5 times in refreshing as compared with Takju made with the cooked rice. However there are no differences between them in flavor and color of Takju. In overall acceptance Takju made with the germed brown rice was shown to be 1.3 times as compared with Takju made with the cooked rice. In conclusion the germed brown rice was expected to be able to be better in Takju quality.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.6
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• pp.807-812
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• 2007

In order to enhance the flavor and storage stability of meat sauce, the manufacturing process of fermented beef-rib sauce was developed in a two-step process. The fermented sauce base was manufactured with Zygosaccharomyces rouxii Y-80 yeast cultivation in raw sauce ingredients for 3 days at $25^{\circ}C$. The fermented beef-rib sauce (FBS) was produced by mixing fermented sauce base with side ingredients. Comparison of the physicochemical and sensory properties with non-fermented beef-rib sauce (NFBS) revealed that the content of ethanol and volatile flavor compounds were higher in FBS; also, the result of sensory evaluation showed that FBS obtained excellent scores for overall taste. To determine the storage stability, FBS and NFBS were incubated at $25^{\circ}C$ for 7 days. The extent of decrease of pH and increase of titratable acidity in NFBS were faster than FBS. After 7 days, ethanol concentrations in FBS and NFBS were 3.77% and 2.04%, respectively. Therefore, based on these results, it can be suggested that storage stability of FBS is superior.

• The Korean Journal of Food And Nutrition
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• v.18 no.3
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• pp.161-167
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• 2005

This study was conducted to examine the possibility of improvement effect in Takju mash added with ${\alpha}G-Hesperidine$ on the second stage mash. Alcohol was highly generated in comparison with the control on fermentation time in case of the ${\alpha}G-Hesperidine$ on the second stage mash. Reducing sugar was also highly produced after 2 days on the second stage, and amount of reducing sugar was indicated to be decreased between $4\~6$ days. Total acidity was shown not to be practically changed after 2 days in mash added with ${\alpha}G-Hesperidine$ on the second stage in comparison with the control. Fusel oil produced from mash added with ${\alpha}G-Hesperidine$ was less generated in comparison with the control. Yeast growth on the mash added with ${\alpha}G-Hesperidine$ was revealed to be highly in comparison with the control through fermentation periods. Precipitation velocity of suspension in mash added with ${\alpha}G-Hesperidine$ was shown to be 1.5 times lower than that of the control. Precipitation amount in mash added with ${\alpha}G-Hesperidine$ was not nearly changed on the storage time. The astringency and bitterness were slightly decreased, while on the other turbidity and refreshing were increased in mash added with ${\alpha}G-Hesperidine$. In general overall preferences was indicated to be fully satisfied in mash added with ${\alpha}G-Hesperidine$ in comparison with the control. Nasty smell of Takju added with ${\alpha}G-Hesperidine$ was recognized after 6 days during storage.