• Research in Plant Disease
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• v.18 no.2
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• pp.109-116
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• 2012

A bacterial strain antagonistic to some fungal phytopathogens was isolated from the stem of a Persimmon tree in Yeongam, Korea. This bacterium was identified as Bacillus subtilis by 16S rRNA gene sequencing and designated as B. subtilis GDYA-1. In in vivo experiment, the fermentation broth exhibited antifungal activities against Magnaporthe oryzae on rice plants, Phytophthora infestans on tomato plants, and Puccinia recondita on wheat plants. We isolated one antifungal compound and its chemical structure was determined by mass and $^1H$-NMR spectral data. The antifungal substance was identified as benzoic acid. It inhibited mycelial growth of M. oryzae, Rhizoctonia solani, Sclerotinia sclerotiorum, and P. capsici with minimum inhibition concentration (MIC) values, ranging from 62.5 to 125 ${\mu}g/ml$. Moreover, the substance effectively suppressed Phytophthora blight of red pepper caused by P. capsici in a pot experiment. To the author's knowledge, this is the first report on the antifungal activity of benzoic acid against phytopathogenic fungi. Benzoic acid and B. subtilis GDYA-1 may contribute to environmental-friendly protect crops from phytopathogenic fungi.

• Food Engineering Progress
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• v.14 no.1
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• pp.14-20
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• 2010

The objective of the current study was to determine the cryoprotective effects of trehaolse on lactic acid bacteria in the frozen yoghurt during long-term frozen storage conditions. The frozen yoghurts were prepared using starter culture containing Lactobacillus bulgaricus and Streptococcus thermophilus, as well as trehalose and sorbitol as a cryoprotectant. The viable cell numbers of lactic acid bacteria in frozen yoghurt did not significantly decreased during six weeks frozen storage conditions. The MRS broth, which contains either trehalose or sorbitol, cultured with L. bulgaricus and/or S. thermophilus, and then the cultured medium was kept in the frozen condition for six weeks. The results indicated that lactic acid bacteria viability significantly increased with trehalose addition (2 and 5%) in the media compared to those of control and sorbitol supplement groups. The lactic acid bacteria viability in the yoghurts was examined on the effects of repeated freeze and thaw events. The freeze-thaw resistance of lactic acid bacteria significantly increased with trehalose supplement in the yoghurt. The major volatile aroma compounds (acetaldehyde, acetone, ethanol, diacetyl, and acetoin) in yoghurt were separated and indentified by headspace GC-FID analysis. Distinct flavor components and their ratios are known as important quality factors for yoghurt notes. Trehalose addition to the yoghurt was not influenced these factors during lactic acid fermentation. The results in this study demonstrated that trehalose potentially can be applicable as an effective cryoprotectant for lactic acid bacteria in the frozen yoghurt products.

• The Korean Journal of Food And Nutrition
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• v.16 no.1
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• pp.7-14
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• 2003

This study mainly focused on to investigate the effects of Schizandra chinensis on the growth of a bacterium, CS6 which was isolated from kimchi. CS6 was final]y identified to lactobacillus plantarum that caused acidification of kimchi. The ethanolic extract of Schizandra chinensis(EES) inhibited the growth of L. plantarum. Minimum inhibition concentration of crude EES on L. plantarum was 62.5mg/$m\ell$. In broth culture, 5$\mu\textrm{g}$/$m\ell$ of EES completely inhibited the growth of L. plantarum during fermentation. The addition of 0.4% of EES has no apparent effect on quality including the taste and color on kimchi. It was expected that EES-containing kimchi could extend the period of preservation. Analysis of organic acids in water fractions of EES was carried out by HPLC. It is apparent that antimicrobial active fractions contained the highest concentration of succinic acid, a little tartaric acid and malic acid. Among these organic acids, succinic acid showed the strong inhibitory effect against L. plantarum CS6 in vitro. Succinic acid-containing kimchi with a concentration of 0.4 and 0.5% had the inhibitory effect on growth of L. plantarum. Inhibitory effect of EES on amylase, cellulase and pectinase was also tested. In conclusion, the present experiment demonstrated that EES inhibited the growth of L. plantarum, and various enzyme activity. EES-containing kimchi was sustained the hardness, and initial acidity during fermentation. EES was considered as the possible additive of kimchi process and EES added in kimchi increase the quality, and storage period of kimchi.

• Food Science and Preservation
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• v.21 no.6
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• pp.892-902
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• 2014

The quality characteristics of Takju were investigated according to the different rice varieties and mixing ratio of Nuruk for the advanced quality of Takju. The yeast was selected by alcohol-producing ability. Then a liquid starter was prepared using brewing fungi (Aspergillus luchuensis 34-1 and Lichtheimia ramosa CN042), and rice Nuruk was manufactured with two rice types (Chucheong and Hanareum). The quality characteristics of Takju were investigated based on the rice type and the mixing ratio of A. luchuensis 34-1 and Lich. ramosa CN042 (1:0, 0:1, 1:1, 1:3). S. cerevisiae Y268 showed an alcohol yield of $9.3{\pm}0.33%$ at a 0.3% concentration in the YPD broth medium, and the rice Nuruk with A. luchuensis 34-1, regardless of rice type, was confirmed to have a higher enzyme activity and physiochemical property than Lich. ramosa CN042. According to the quality analysis of Takju, the physiochemical property was increased for the fermentation period, and the acidity differed by type of fungi and rice. The quality of Takju was changed with the composition differences of organic acid and free amino acid by rice type and mixing ratio. As a result of the sensory evaluation of Takju, the preference for it was increased with the Hanareum and A. luchuensis 34-1, respectively. Thus, this study shows the possibilities for activating the industry of traditional liquor by improving the Nuruk and Takju manufacturing technique.

• Journal of Food Hygiene and Safety
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• v.16 no.4
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• pp.274-279
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• 2001

Generally, non-aflatoxigenic fungi, such as Aspergillus oryzae, and Aspergillus are main microflora in Korean traditional fermented foods including Meju and soybean paste, but sometimes, Aspergillus flavus and Aspergillus parasiticus can be contaminated and accumulated aflatoxins during fermentation and storage. So the screening of aflatoxigenic strains in fermented traditional food is very important to improve the sanitary quality of those foods. In this work, we screened aflatoxin producing fungi from commercial Meju and soybean paste in Western Gyeongnam by immunoassay. Samples were randomly purchased from market of the commercial Meju(10 EA) and soybean paste(20 EA) in nine areas of Western Gyeongnam. Of the samples collected,24 strains and 22 strains of Aspergillus sp. were isolated from Meju and soybean paste, respectively. The isolated strains were cultured on SLS media at $25^{\circ}C$ for 15 days. The cultured broth were extracted with ethyl acetate and were analysed to determine aflatoxin B$_1$(AFB$_1$) by direct competitive ELISA(DC-ELISA). Six strains(25%) isolated from Meju, and 2 strains(9%) isolated from saybean paste, were confined as aflatoxin producing strains. The average range of aflatoxin productivity of isolates from Meju was 54.6 $\pm$ 38.7 ng/ml and that from soybean paste was 11.1 $\pm$ 8.6 ng/ml, respectively. Among them, isolated strain No. M-5-4 produced a high level of AFBl and showed 98.26 ng/ml of AFB$_1$. Every isolates were also re-confined their AFB$_1$productivity by thin layer chromatography(TLC). The TLC results also showed same trend as DC-ELISA results. As the above results, the screening of hazard mycotoxigenic fungi from traditional fermented foods should be necessary for the safety and the application of HACCP system in the food manufactory in Korea.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.344-357
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• 2020

Strain improvement and bioprocess development were undertaken to enhance hyaluronic acid(HA) production by Streptococcus zooepidemicus cells. Using a high-yielding mutant strain, statistical medium optimization was carried out in shake flask cultures, resulting in 52% increase in HA production (5.38 g/l) at the optimal medium composition relative to the parallel control cultures. For sufficient supply of dissolved oxygen (DO), which turned out to be crucial for enhanced production of HA, agitation system and speed were intensively investigated in 5 L bioreactor cultures. Increase in oxygen mass transfer coefficient (k_La) through increment of agitation speed (rpm) and 35% expansion of diameter of the newly-designed impellers showed significantly positive effects on HA production. By installing an expanded Rushton-turbine impeller for efficient break-down of sparged air, and an extended marine impeller above the Rushton-turbine impeller for efficient mixing of the air-born viscous fermentation broth, maximum amount of HA (9.79 g/l) was obtained at 450 rpm, 1.8 times higher level than that of the corresponding flask culture. Subsequently, the possibility of bioprocess scale-up to a 50 L bioreactor was investigated. Despite almost identical maximum HA production (9.11 vs 9.25 g/l), the average HA volumetric productivity (r_p) of the 50 L culture turned out only 74% compared to the corresponding 5 L culture during the exponential phase, possibly caused by shear damages imposed on the producing cells at the high stirring in the 50 L culture. The scale-up process could be successfully achieved if a scale-up criterion of constant oxygen mass transfer coefficient (k_La) is applied to the 50 L pilot-scale bioreactor system.

• Korean Journal of Food Science and Technology
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• v.21 no.1
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• pp.154-163
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• 1989

This studies were designed to improve the productivity of L-lysine by protoplast fusion and immobilized system of fusants using strains of Brevibacterium flavum ATCC 21528, Brevibacterium lactofermentum ATCC 21086 and Corynebacterium glutamicum 820. Mutants were isolated with concentration method of $300{\mu}g/ml$ penicillin-G after treatment of $250{\mu}g/ml$ N-methyl-N-nitro-N-nitrosoguanidine. B. flavum $37-2(Hos^-,\;Kan^r,\;AEC^r)$, B. lactofermentum $6-2(Ile^-,\;Val^-,\;Str^r,\;AEC^r)$ and C. glutamicum 57-5$(Met^-,\;Thr^-,\;Rif^r,\;AEC^r)$ were isolated from mutants. Protoplasts were induced by being incubated with $500{\mu}g/ml$ lysozyme of lysis solution for 6 hr and the ratio of protoplast formation and regeneration were ranging from 97-99% and 33-37%, respectively. Fusion frequencies of fusants of BBFL 21, BCFG 37 and BCLG 59 were shown in the range from $1.25{\times}10^{-6}\;to\;5.83{\times}10^{-7}$ under the optimum conditions. The fusant BBFL 21 showed the highest productivity of $411.1\;ng/ml{\cdot}hr$ L-lysine in the lysine productivity broth at $30^{\circ}C$ for 72hr. In the immobilization systems, fusant BBFL 21 was employed in various polymer matrices such as sodium alginate, polyacrylamide, agar and ${\alpha}-carrageena$. The immobilization of sodium alginate showed the highest productivity of $413\;ng/ml{\cdot}hr$ L-lysine in the batch system. Continuous fermentation of immobilization system by using tube fermentor was produced the highest productivity $416.7\;ng/ml{\cdot}hr $ L-lysine under optimum condition.