• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.8
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• pp.1118-1123
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• 2009

Brown-rice hydrolyzates with different degrees of hydrolysis (DH) were fermented using Leuconostoc mesenteroides (Ln. mesenteroides) KC51 strain at $30^{\circ}C$ for 15 hr. Changes in pH, titratable acidity, viable cell counts and phytate degradation during fermentation were investigated. The acid production was increased with increasing DH of brown-rice hydrolyzate. At high DH (48.2%), the pH and titratable acidity reached to pH 3.41 and 0.82% after 15 hr fermentation, respectively. Regardless of DH of brown-rice, however, the viable cell population of Ln. mesenteroides KC51 was slightly increased to $4.0\sim7.2{\times}10^8$ CFU/g during the 6 hr of cultivation. The phytate content in brown-rice hydrolyzates decreased with increasing DH of brown-rice hydrolyzates. The level of phytate was reduced to around 50% of initial concentration at high DH condition. When the fermented brown-rice was kept at $4^{\circ}C$, pH, titratable acidity and number of viable cells were nearly maintained for 14 days.

• Microbiology and Biotechnology Letters
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• v.31 no.3
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• pp.277-283
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• 2003

A bacterium producing the extracellular mannanase was isolated from Korean soybean paste. The isolate WL-7 has been identified as Bacillus subtiis on the basis on its 16S rRNA sequence, fatty acid composition, morphology and biochemical properties. The mannanase of culture supernatant was the most active around $55^{\circ}C$ and pH $6.0^{\circ}C$, and retained 90% of its maximum activity at range of pH 5.0∼7.5 and $50∼60^{\circ}C$. The additional carbohydrates including lactose, $\alpha$-cellulose, avicel, locust bean gum (LBG), wheat bran and konjak increased dramatically the mannanase productivity of strain WL-7. Especially, the maximum mannanase productivity was reached to 224 U/ml in LB medium supplemented with both 0.5% LBG and 0.5% konjak, which was approximately 200-folds more than that in LB medium. It was suggested that the increase of mannanase production was owing to induction of mannanase biosynthesis by both LBG and konjak hydrolysates transported following initial hydrolysis by extracellular mannanase during the cell growth.

• Microbiology and Biotechnology Letters
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• v.44 no.3
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• pp.363-369
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• 2016

A putative cyclomaltodextrinase gene (licd) was found from the genome of Listeria innocua ATCC 33090. The licd gene is located in the gene cluster involved in maltose/maltodextrin utilization, which consists of various genes encoding maltose phosphorylase and sugar ABC transporters. The structural gene encodes 591 amino acids with a predicted molecular mass of 68.6 kDa, which shares less than 58% of amino acid sequence identity with other known CDase family enzymes. The licd gene was cloned, and the dimeric enzyme with C-terminal six-histidines was successfully produced and purified from recombinant Escherichia coli. The enzyme showed the highest activity at pH 7.0 and 37℃. licd could hydrolyze β-cyclodextrin, starch, and maltotriose to mainly maltose, and it cleaved pullulan to panose. It could also catalyze the hydrolysis of acarbose to glucose and acarviosine-glucose. In particular, it showed significantly higher activity towards β-cyclodextrin and maltotriose than towards starch and acarbose. licd also showed transglycosylation activity, producing α-(1,6)- and/or α-(1,3)-linked transfer products from the acarbose donor and α-methyl glucopyranoside acceptor.

• Korean Journal of Food Science and Technology
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• v.23 no.6
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• pp.732-738
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• 1991

Corsoy 79 soybeans were ground into 8-(coarse) and 24-mesh (fine) full-fat soy flours. From the particle size analysis, the 8-mesh full-fat soy flours were found to have larger values for geometric mean diameter and geometric standard deviation. However, the distribution moduli of coarse and fine soy flours were similar and indicated soybeans were nearly 'brittle'. Development of hydrolytic and oxidative rancidities of coarsely and finely ground full-fat soy flours were followed from grinding to 24 hrs later. No increases in peroxide value and conjugated dienes in the oil and hexanal content in the headspace of the flour were observed when the moisture was 10.7% or less. At 14.9% moisture and above, lipid oxidation increased with increased moisture content and storage time. Free fatty acid contents increased slightly at all moisture contents. However, hydrolysis did not exceed 0.06% over the moisture range of 4 to 18%, which is of little practical significance. Fine grinding increased oxidative and hydrolytic rancidities, especially at 14.9% moisture and above. these findings indicate that raw soybeans can be ground to full-fat soy flours and stored up to 24 hrs without undergoing significant lipid and flavor deterioration if the moisture content is 11% or less.

• Korean Journal of Food Science and Technology
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• v.41 no.5
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• pp.522-527
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• 2009

The principal objective of this study was to assess the effects of various manufacturing conditions of soy sauce containing hydrolyzed vegetable protein (HVP) (HVP-soy sauce) on 3-monochloropropane-1,2-diol (3-MCPD) contents. Various HVP soy sauces were prepared under different conditions of alkaline treatment and retention process. Derivatives of heptafluorobutylimidazole (HFBI) 3-MCPD were determined via GC/MS below $0.010{\mu}g/g$, which was sensitive with a good recovery rate. The quantity of 3-MCPD decreased with the pH and temperature of alkaline treatment, and the time and temperature of the retention process increased. Alkaline treatment at pH 10.0-10.5 and a 72 hr retention process were shown to reduce effectively the 3-MCPD contents of HVP-soy sauces. This result indicates that the manufacturing process, particularly alkaline treatment, and retention process would be critical steps in managing 3-MCPD contents in HVP-soy sauce.

• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.287-294
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• 2008

Three amino acid residues (His119, Glu164, and Glu338) in the active site of Thermus caldophilus GK24 ${\beta}$-glycosidase (Tca ${\beta}$-glycosidase), a family 1 glycosyl hydrolase, were mutated by site-directed mutagenesis. To verify the key catalytic residues, Glu164 and Glu338 were changed to Gly and Gln, respectively. The E164G mutation resulted in drastic reductions of both ${\beta}$-galactosidase and ${\beta}$-glucosidase activities, and the E338Q mutation caused complete loss of activity, confirming that the two residues are essential for the reaction process of glycosidic linkage hydrolysis. To investigate the role of His119 in substrate binding and enzyme activity, the residue was substituted with Gly. The H119G mutant showed 53-fold reduced activity on 5mM p-nitrophenyl ${\beta}$-D-galactopyranoside, when compared with the wild type; however, both the wild-type and mutant enzymes showed similar activity on 5mM p-nitrophenyl ${\beta}$-D-glucopyranoside at $75^{\circ}C$. Kinetic analysis with p-nitrophenyl ${\beta}$-D-galactopyranoside revealed that the $k_{cat}$ value of the H119G mutant was 76.3-fold lower than that of the wild type, but the $K_m$ of the mutant was 15.3-fold higher than that of the wild type owing to the much lower affinity of the mutant. Thus, the catalytic efficiency $(k_{cat}/K_m)$ of the mutant decreased to 0.08% to that of the wild type. The $k_{cat}$ value of the H119G mutant for p-nitrophenyl ${\beta}$-D-glucopyranoside was 5.l-fold higher than that of the wild type, but the catalytic efficiency of the mutant was 2.5% of that of the wild type. The H119G mutation gave rise to changes in optima pH (from 5.5-6.5 to 5.5) and temperature (from $90^{\circ}C\;to\;80-85^{\circ}C$). This difference of temperature optima originated in the decrease of H119G's thermostability. These results indicate that His119 is a crucial residue in ${\beta}$-galactosidase and ${\beta}$-glucosidase activities and also influences the enzyme's substrate binding affinity and thermostability.

• Microbiology and Biotechnology Letters
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• v.45 no.3
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• pp.218-225
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• 2017

Saeu (shrimp) jeotgal (SJ) was prepared by mixing with 25% salt with different types: purified salt (PS), solar salt aged for 1 year (SS), and bamboo salt. SJ was fermented for 22 weeks at $15^{\circ}C$. Bacilli and marine bacteria were detected throughout the entire fermentation period, and marine bacteria were present in the largest numbers. Lactic acid bacteria (LAB) were detected only during the first 8-10 weeks, but yeasts appeared at the sixth week and later. Archaea were detected in low numbers only from SS-SJ during the first 8 weeks. BS- SJ showed higher pH and lower titratable acidity (TA) values than other SJs because of strong alkalinity of bamboo salt. Amino-type nitrogen (ANN) contents of SJs increased during fermentation, especially, after 2 and 6 weeks. SS-SJ showed the highest ANN content from the beginning to the end of fermentation. Ammonia-type nitrogen (AMN) contents also increased like the amino-type nitrogen during fermentation. The highest volatile basic nitrogen (VBN) was also observed in SS-SJ. Salinity was kept constant after 4 weeks. SS was better than other salts for SJ fermentation in terms of protein hydrolysis.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.303-309
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• 2020

The purpose of this study was to identify the changes in the components of unfermented Gongjin-dan (GD) and fermented Gongjin-dan (FGD) and to confirm whether GD or FGD has an inhibitory effect on viral neuraminidase (NA) activity. A major component of FGD was isolated and identified as nodakenetin, which is the aglycone of nodakenin. After fermentation, the nodakenetin content in FGD was approximately 10-fold higher than that in GD. Then, we examined the viral NA-inhibitory activity of GD, FGD, nodakenin, and nodakenetin. At a concentration of 500 ㎍/ml, FGD inhibited viral NA activity by 92% compared to the DMSO-treated control, while GD barely inhibited viral NA activity. In addition, 250 ㎍/ml of nodakenetin inhibited viral NA activity by 68% compared to the control, while nodakenin inhibited viral NA activity by only 4% at the same concentration as nodakenetin. Collectively, these results suggest that FGD has a more remarkable viral NA-inhibitory activity than GD because the content of the anti-viral component nodakenetin was higher in FGD due to the hydrolysis of nodakenin by Lactobacillus plantarum KCTC 3104.

• Journal of Nutrition and Health
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• v.42 no.8
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• pp.740-749
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• 2009

The objectives of this study was to determine whether a new physically modified cornstarch by ultra-fine- or nanoscale pulverizer to reduce particle size offers better bioactive function than native cornstarch in weanling Sprague-Dawley rats. Male weaning Sprague-Dawley rats were fed diets containing native cornstarch (NAC), ultra fine pulverized cornstarch (UFC) or nano-scale pulverized cornstarch (NSC) for 4 weeks. In vitro rate of starch hydrolysis, growth performance, organ weight, intestine length intestinal proliferation and the fermentation by Bifidobacterium of rat cecum were evaluated. The diet with reduced particle size (UFC or NSC) significantly increased body weight gain and organ weight. Feed efficiency was increased in NSC fed rats and was not affected in UFC fed rats. Intestinal proliferation was decreased in NSC group. Reduction of particle size also increased cecal short chain fatty acid concentration and the growth and acidifying activity of Bifidobacterium. It is concluded that a reduction of particle size of starch granules by physically modification may increase growing performance and gut function.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.93-98
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• 2017

The fixing behaviors of raw silk yarns treated with melamine and formaldehyde at a molar ratio of 1:3 for trimethylolmelamine were investigated. Sericin was fixed during the fixing process, but a part of sericin I was removed simultaneously by hot water. The weight losses by fixing and the degumming losses by degumming greatly decreased with increasing concentrations of melamine and formaldehyde. The silk yarns fixed with 0.011 M melamine and 0.033M formaldehyde were significantly degummed due to the insufficient fixation of sericin and the alkaline hydrolysis of sericin by sodium carbonate during the degumming process. On the other hand, the silk yarns fixed with 0.055M melamine and 0.165M formaldehyde were degummed slightly (the degumming losses of 3-8%) due to the strong fixation of sericin, which might result from the many cross-linkages between the sericin I molecules, which were formed by trimethylolmelamine. Those fixed with the fixing solution containing 15% owf softener showed the lowest weight and degumming losses because under the condition of 15% owf softener, the cation of the softener can effectively form ionic bonds with the negatively charged side chain of aspartic acid in sericin. In addition, van der Waals' forces may be also formed between the hydrophobic tail of the softener and the hydrophobic region of sericin, which may help inhibit the removal of sericin I.