• Preventive Nutrition and Food Science
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• v.1 no.1
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• pp.41-45
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• 1996

This study was conducted to develop the fermentation kinetic model for the prediction of acidity and pH changes in Kimchi as a function of fermentation temperatures. The fitness of the model was evaluated using traditional two-step method and an alternative non-linear regression method. The changes in acidity and pH during fermentation followed the pattern of the first order reaction of a two-step method. As the fermentation temperature increased from 4$^{\circ}C$ to 28, the reaction rates of acidity and pH were increased 8.4 and 7.6 times, respectively. The activation energies of acidity and pH were 16.125 and 16.003kcal/mole. The average activation energies of acidity and pH using a non-linear method were 16.006 by the first order and 15.813 kcal/mole by the zero order, respectively. The non-linear procedure had better fitting 개 experimental data of the acidity and pH than two-step method. The shelf-lives based on the time to reach the 1.0% of acidity were 33.1day at 4$^{\circ}C$ and 2.8 day 28$^{\circ}C$.

• Journal of Microbiology and Biotechnology
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• v.33 no.10
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• pp.1257-1267
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• 2023

Although rational genetic engineering is nowadays the favored method for microbial strain improvement, building up mutant libraries based on directed evolution for improvement is still in many cases the better option. In this regard, the demand for precise and efficient screening methods for mutants with high performance has stimulated the development of biosensor-based high-throughput screening strategies. Genetically encoded biosensors provide powerful tools to couple the desired phenotype to a detectable signal, such as fluorescence and growth rate. Herein, we review recent advances in engineering several classes of biosensors and their applications in directed evolution. Furthermore, we compare and discuss the screening advantages and limitations of two-component biosensors, transcription-factor-based biosensors, and RNA-based biosensors. Engineering these biosensors has focused mainly on modifying the expression level or structure of the biosensor components to optimize the dynamic range, specificity, and detection range. Finally, the applications of biosensors in the evolution of proteins, metabolic pathways, and genome-scale metabolic networks are described. This review provides potential guidance in the design of biosensors and their applications in improving the bioproduction of microbial cell factories through directed evolution.

• Korean Journal of Food Science and Technology
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• v.25 no.5
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• pp.502-509
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• 1993

Changes in microflora and enzyme activities of 3 kinds of traditional kochujang were investigated during 6 months of fermentation. Tested kochujang included Sunchang kochujang prepared with glutinous rice, Boeun kochujang prepared with barley and Sachun kochujang prepared with wheat. The pH in Sunchang and Sachun kochujang showed a slighlt decrese during fermentation. In contrast, pH of Boeun kochujang decreased rapidly up to 90 days of fermentation and then leveled off thereafter. The final pH values of Sunchang, Boeun and Sachun kochujang were 4.7, 4.0, and 4.6, respectively. The viable cell counts of aerobic bacteria in Sunchang and Sachun kochujang did not show remarkable changes during fermentation, however, those in Boeun kochujang showed a rapid increase up to 60 days of fermentation and stabilized. On the other hand, the viable cell counts of anaerobic bacteria decreased after 120 days of fermentation. Yeasts were found in different traditional kochujang at different time during the first 60 days of fermentation. It was found that ${\alpha}-$, ${\beta}-$, and glucoamylase activities of Sachun kochujang were higher than those of Sunchang and Boeun kochujang during fermentation. Acidic and neutral proteases showed the highest activity during $30{\sim}60\;days$ and $60{\sim}90\;days$ of fermentation, respectively. Sunchang kochujang showed the highest activity of acidic protease followed in decreasing order by Sachun and Boeun kochujang. On the other hand, Boeun kochujang showed the highest activity of acidic protease followed in decreasing order by Sachun and Sunchang kochujang.

• Korean Journal of Food Science and Technology
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• v.32 no.1
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• pp.187-191
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• 2000

This study was performed to examine the effects of salt addition level on the changes in physicochemical properties of the salted and fermented shrimp during fermentation. Amino nitrogen content increased with the fermentation time, and was higher at low salt addition level. Volatile basic nitrogen content in the fermented shrimp with 3 and 8% salt increased rapidly at initial fermentation period, but decreased at 6 week fermentation and remained constant afterward, while that with 18 and 30% salt maintained its initial level through 22 week fermentation. Thiobarbituric acid(TBA) value decreased rapidly in the early stage of the fermentation, but slightly increased after 4-6 week fermentation. The TBA value was higher at lower salt level after 6 week fermentation. Peroxide value of the fermented shrimp with salt content higher than 8% increased rapidly at 2-4 week fermentation and decreased sharply at 6 week, while that with 3% salt showed the maximum value at 10 week fermentation.

• The Korean Journal of Food And Nutrition
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• v.26 no.1
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• pp.146-149
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• 2013

This study was performed to identify the effect of lactic-fermentation of peanut milk on n-hexanal content. Changes in viable cell populations, pH and titratable acidity indicated that there was a synergistic interaction between Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus during fermentation. The analysis of headspace volatiles revealed that n-hexanal nearly disappeared due to fermentation. S. salivarius subsp. thermophilus was more effective than L. delbrueckii subsp. bulgaricus in reducing the n-hexanal content.

• The Korean Journal of Food And Nutrition
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• v.9 no.3
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• pp.289-293
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• 1996

Population changes of aerobic bacteria and lactic acid bacteria and changes of pH, acidity, and total sugar content were creased from initial period of fermentation. Lactic acid bacteria Increased during the first one nay rapidly and thereafter they creased slowly thereafter. Acidity increased on the third day of fermentation. Acidity was very low In Kimchi containing both Total sugar content decreased gradually from initial period to late period of fermentation.

• The Korean Journal of Food And Nutrition
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• v.12 no.1
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• pp.1-6
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• 1999

The strain isolated for making chungkuk-jang was Bacillus subtilis which formed sport with 98% ratio. Logarithmical culture was inoculated(1,000 CF/g) to the steamed soybeans and at th optimum fer-mentation conditions(4$0^{\circ}C$, RH 90%) fermentation progressed very rapidly and synchronously. Fermen-tation time was 24 hours on the optimum fermentation conditions. During activated fermentation chun-gkuk-jang's aroma and flavor created. After finishing the fermentation the spore forming ratio was 95% and replenishment was not occured easily during aging at the below 5$^{\circ}C$.

• Korean Journal of Food Science and Technology
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• v.35 no.2
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• pp.272-279
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• 2003

To determine optimal fermentation period of wild vegetables mixed with black sugar without microorganisms during plant extract fermentation food processing, changes in chemical components, quality characteristics of the fermented broth, and physiological functionality during fermentation period were investigated. pH and $^{\circ}Bx$ of fermented broths decreased gradually during fermentation period. Except persimmon leaf, viscosity of fermented broths of wild vegetables decreased after 3 months fermentation period. Amylase activity increased to $167{\sim}800%$ of its initial level after 6 months fermentation period, and invertase activity decreased by $60{\sim}170$ units after 1 month fermentation. No significant level of cellulase activity was observed. In the sensory evaluation test, inherent flavors and tastes of the wild vegetable decreased during the fermentation period, while those of others gradually increased. Overall acceptability was the highest after 3 months fermentation. Content of total phenolic compounds and electron-donating ability were highest after 3 to 4 months fermentation period, and decreased thereafter. Except Mugwort, tyrosinase inhibitory activity was found in all fermented broths. SOD-like activities were $23.0{\sim}25.1$ and $27.0{\sim}29.2%$ in fermentation broths of acacia flower and persimmon leaf, respectively, and were maintained throughout the fermentation period. Based on these results, fermentation period of 3 to 4 months was determined to be appropriate for plant extract fermentation food processing.

• Food Science and Preservation
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• v.7 no.2
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• pp.233-239
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• 2000

To proceed mass production and improve its quality, we fermented potatoes using pilot system and investigated the changes in components during fermentation. After liquefaction and saccharification of potatoes by Nuruk(group I), crude enzyme(group II) and glucoamylase(group III), sugar contents in all groups were 18brix equally. However sugar contents in group(II) and group(III) after 24hrs decreased deeply to 7.2 and 8.8 % respectively, after 24hrs. Alcohol content in group(I) increased slowly and was the highest such as 6.8% after 48hrs. Fusel oils in all groups were n-propanol, isobutanol and isoamylalcohol. The major fusel oil in all groups was isoamylalcohol. At the early stage of fermentation, free sugars were glucose, maltose and lactose. Glucose decreased deeply during fermentation and at latter of the fermentation, galactose was detected in all groups. The contents of total free amino acid were 516.57~569.98 mg% in group(I), 193.97~292.11 mg% in group (II) and 186.31~270.53 mg% in group(III). The contents of aspartic acid, serine, glutamic acid, alanine, arginine, and histidine were high in all groups.

• Food Science and Preservation
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• v.14 no.1
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• pp.100-104
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• 2007

This study was designed to investigate quality characteristics and conditions of acetic acid fermentation of kiwi vinegar following addition of oligosaccharide. During the acid fermentation alcohol concentration and total acidity were shown to be 6% and 1.0%, respectively, with the highest acetic acid yield. Acetic acid fermentation of kiwi following addition of oligosaccharide showed the highest acetic acid yield with 15% oligosaccharide. Free forms of sugars in kiwi vinegar were detected to be fructose, glucose and maltose. Organic acid of kiwi vinegar were malic, lactic, acetic, citric and succinic acid. Total content of organic acid was shown to be the highest with 15% oligosaccharide. Mineral content was shown to be lower when oligosaccharide amount was increased. In conclusion, oligosaccharide addition has an insignificant effect on acetic acid fermentation of kiwi, and was evaluated to be suitable at 15%.