• Food Science and Preservation
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• v.5 no.1
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• pp.13-21
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• 1998

Korean medicinal herb extracts(KMHE) were applied to the preservation of greenhouse produce in order to prove their effectiveness. KMHE showed remarkable antimicrobial effects against Bacillus cereus, Peudomonas syringae, and Corynebacterium xerosis causing the postharvest decay of greenhouse produce. Among KMHE the extracts of Rheum palmatum L. and Coptis chinensis Franch most obviously inhibited the growth of microorganims causing the Postharvest decay of greenhouse produce, which destroyed to undetectable levels when treated with more than 500ppm of KMHE. The activities of KMHE were stable in the wide spectrum of pH and temperature. Direct visualization of microbial cells by using both transmission electron microscope and scanning electron microscope showed microbial cell membrane the function of which was destroyed by treating with the dilute solutions of KMHE. This change of cellular membrane permeability could be identified in the experiment that O-nitrophenyl-$\beta$-D-galactopyranoside(ONPG), the artificial substrate of $\beta$-galactosidase, was hydrolyzed in the presence of KMHE, indicating that the membrane was perturbed by KMHE.

• Microbiology and Biotechnology Letters
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• v.18 no.1
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• pp.39-43
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• 1990

The inhibitor had the inhibitory activities against hydrolysis of PNPG, sucrose and ONPG by $\alpha$-Dglucosidase, $\alpha$ - and $\beta$ -galactosidase, but it did not inhibit amylases and other carbohydrases. Kinetic studies exhibited that the inhibitory substance non-competitively inhibited the enzyme reaction with a Ki value of 118 $\mu$g/m$\ell$, and enzyme-inhibitor complex was formed slowly.

• Food Science and Preservation
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• v.11 no.3
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• pp.417-423
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• 2004

Botanical antimicrobial agent-grapefruit seed extract mixture (BAAG) have an unknown compounds which exhibit the antibiotic activities aganist microorganisms including bacteria and fungi. We have examined the effects of BAAG on the physiological function of Botrytis cinerea which was isolated from necrotic lesions of decayed fruits and vegetables such as cucumbers, grapes, tomatoes, and red peppers during storage. In the results of enzymatic activities related to the energetic metabolism there was no inhibitory effect of BAAG on the activities of several enzymes in vitro including glucose 6-phosphate dehydrogenase and malate dehydrogenase, while there was inhibitory effect of BAAG on the activities of hexokinase and succinate dehydrogenase. O-nitrophenyl-$\beta$-D-galactopyranoside(ONPG), the artificial substrate of $\beta$-galactosidase was hydrolyzed in the presence of BAAG, indicating that the membrane was pertubated by the BAAG. From the results we suggested that the antibiotic activity of BAAG is due to the change of membrane permeability of the cell. BAAG was fractionated and purified by silica gel and sephadex column chromatography. Among active fractions two peaks were identified as naringin and limonin when they were analyzed by by NMR and Fast atomic bombardment.

• Korean Journal of Food Science and Technology
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• v.22 no.4
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• pp.426-433
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• 1990

The conditions for immobilization of the partially purified ${\beta}-galactosidase$ form Bacillus subtilis HP4 and the properties of the immobilized enzyme have been investigated. The crude enzyme precipitated with cold acetone was purified about 68-fold through DEAE-cellulose and sephadex G-100 chromatography and its recovery was 19.9% The optimal conditions for Immobilization of enzyme were obtained in 2%(w/v) sodium alginate, 15%(v/v) enzyme solution and 2%(w/v) calcium chloride, and also the optimal stirring thme was 2 hours on the above conditions. The optimum temperature and pH values for immobilized enzyme were $55^{\circ}C$ and 6.5, respectively. Its residual activity was show 25% after heat treatment for an hour at $65^{\circ}C$, and found its high stability in pH 6.0 to 8.0. The enzyme activity was not affected b)· EDTA, 2-mercaptoethanol, KCN, protective agents, and other methal ions except Hg ion and Cu ion. The $K_m\;and\;V_{max}$ values of the immobilized enzyme on ONPG were $1.82{\times}10^{-2}M\;and\;3.57{\times}10^{-8}mole/min$, whereas those on lactose were $2.94{\times}10^{-2}M\;and\;1.68{\times}10^{-7} mole/min$, respectively. The remained enzyme activity for the immobilized enzyme was 95%t of original activity after storage of 40 days at $4^{\circ}C$, and when reused for 5 times was 81%. When skim milk(4.8% lactose) and 5% lactose solution were reacted with the immobilized enzyme(250 units/g) of lactose were 51% and 43%, respectively.

• Korean Journal of Environmental Biology
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• v.25 no.1
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• pp.34-41
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• 2007

A study on the distribution of V. parahaemolyticus among sea water, sea mud, and marine products in Hwabuk, Samyang, Daepo, Jungmun, Pyoson, Anduk, Aewol, and Gwakji on the coastal area of Jeju island was conducted from January to December in 2002. The 2,880 total specimens of 960 sea waters, 960 sea mud, 960 marine products were collected and studied for the rate of isolation of V. parahaemolyticus, and biochemical, serological and antibiotic sensitivity tests were performed. A total of 417 strains of V. parahaemolyticus were isolated and identified from 2,880 total specimens. In the test of biochemical properties, 100 of V. parahaemolyticus isolates in the presence of 0.85% NaCl were positive in the utilization of lysine, ornithine, indole, glucose, and mannitol, and negative in the utilization of ONPG, arginine, sodium citrate, urea, tryptophane, inositol, sorbitol, rhamnose, sucrose, and melibiose, $H_2S$ production and VP reaction, while positive or negative in gelatin liquefaction and utilization of amygdalin or arabinose. The isolation rates to the specimen were 161 strains (16.8%) from 960 of sea waters, 137 strains (14.3%) from 960 of sea mud, and 119 strains (12.4%) from 960 of marine products. The isolation rates of V. parahaemolyticus from 8 coastal areas were 14.4% (52/360) in Hwabuk area, 15.3% (55/360) in Samyang area, 13.6% (49/360) in Daepo area, 18.3% (66/360) Jungmun area, 13.1% (47/360) in Pyosun area, 16.4% (59/360) in Anduk area, 12.5% (45/360) in Aewol area and 12.2% (44/360) in Gwakji area, respectively. The distribution of 417 V. parahaemolyticus, isolates was high at Jungmun with 18.3% (66/360), and from sea water with 16.8% (161/960).

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.4
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• pp.32-39
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• 1986

A strain of Aspergillus niger CAD 1 which produces considerable amount of beta-galactosidase was selected from extracellular beta-galctaosidase producing fungi isolated from soil. Optimal conditions for the enzyme from Aspergillus niger CAD 1 were the growth in wheat bran supplemented with 0.5% skim milk powder at $30^{\circ}C$ for 72 hrs. The crude enzyme was purified 1,387 fold through DEAE-cellulosc and Sephadex G-100 chromatographr and its recovery was 6.2%, The optimal pH and temperature for the purified enzyme were pH 4.5 ana $45^{\circ}C$, respectively. The Km and Vmax on ONPG were $3.57{\times}10^3M$ and 33.0 unit/mg protein, whereas those on lacose were $83.3{\times}10^3M$and 15.33 unit/mg protein, respectively, The activation energy for the enzyme was 9,900 cal/mol and the enzyme had no metal ion requirement for its activity and stability. The hydrolysis of lactose in skim milk, 4.8% lactose solution and acidic whey were 65%, 70% and 78% after 10 hrs incubation at $45^{\circ}C$, when 182 units of the enzyme were used 50ml of the substrate solutions.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.985-990
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• 1995

Grapefruit seed extracts(GFSE) have some unknown compounds which exhibit the antibiotic activities aganist microorganisms including bacteria and fungi. We have examined the effects of GFSE on the growth of Enterobacter pyrinus which was isolated from necrotic lesions of pear trees. During the cultivation, the growth of the bacteria was strongly inhibited at the low concentration(0.01%, w/w) of GFSE. Hydrophobic fraction extracted from GFSE by mixed solvents (chloroform : methanol : water, 1 : 2 : 0.8, v/v/v) had components which inhibited the growth of bacteria. There was, however, no inhibitory effect of GFSE on the activities of several enzymes including hexokinase, glucose 6-phosphate dehydrogenase, malate dehydrogenase and succinate dehydrogenase. $O-nitrophenyl-{\beta}-D-galactopyranoside(ONPG)$, the artificial substrate of ${\beta}-galactosidase$ was hydrolyzed in the presence of GFSE, indicating that the membrane was pertubated by the GFSE. From the results it was suggested that the antibiotic activity of GFSE is due to the change of membrane permeability of cell. GFSE was fractionated by high performance liquid chromatography equipped with $C_{18}$ reverse phase column. Among active fractions, three peaks were identified as 1-chloro-2-methyl-benzene (o-toluene), N,N-dimethyl-benzenemethaneamine, 1-[2-(2-ethylethoxy)ethoxy]-4- (1,1,3,3-tetramethyl)-bezene, respectively, while the other three remained unidentified.

• Korean Journal of Food Science and Technology
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• v.33 no.5
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• pp.574-581
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• 2001

The microbial properties and acid tolerance of the three kinds of Acetobacter sp. isolated from persimmon vinegar were investigated. Acid tolerance was also evaluated. Acetobacter sp. were gram negative, short rod, nonspore forming and motile. They reacted positively catalase, methyl red, oxidation fermentation, Voges-Proskauer and nitrate reduction tests and negative to hydrogen sulfide test and ONPG. Acetobacter sp. showed normal growth curve in Carr broth and there was no significant difference between isolates and (standard on) typical strains such as Acetobacter aceti (KCTC1010), Acetobacter liquefaciens (KCTC2804), Acetobacter diazotrophicus (KCTC 2859). Optimum temperature and initial ethanol concentration in incubation were $30^{\circ}C$ and 6%, respectively. Growth and acid production of Acetobacter sp. were suppressed by the concentration of above 4% acetic acid. The amount of $Mg^{++}$ release from Acetobacter sp. cells in medium was increased by acetic acid, and almost in the concentration of 6% acetic acid. Glycolysis by Acetobacter sp. had optimal pH about 6.0 to 7.0 and more stable in acidic condition than in alkalic. The $H^+-ATPase$ of Acetobacter sp. S-1 and S-3 showed a maximal activity between pH values of approximately 5.5 to 7.5 and 6.0 to 7.5, respectively.

• Journal of Microbiology and Biotechnology
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• v.16 no.8
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• pp.1325-1329
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• 2006

Structural modeling of $\beta$-galactosidase from L. lactis ssp. lactis 7962 has shown that the residues Cys-472 and His-509 are located in the wall of the active-site cavity. To examine the functions of Cys-472 and His-509, we generated five site-specific mutants: Cys-472-Ser, Cys-472-Thr, Cys-472-Met, His-509-Asn, and His-509-Phe. $\beta$-Galactosidase substituted at Cys-472 with Met or His-509 with Phe had <3% of the activity of the native enzyme when assayed using ONPG as substrate. The other mutants Cys-472-Ser, Cys-472-Thr, and His-509-Asn had ca. 10-15% of the native enzyme activity. The V$_max$ values of the five mutated enzymes were lower (60-7,000-fold) than that of native enzyme. These results show that the catalytic ability of $\beta$-galactosidase is significantly affected by mutations at Cys-472 or His-509.

• Microbiology and Biotechnology Letters
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• v.23 no.6
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• pp.710-716
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• 1995

$\beta $-1, 4-D-arabinogalactanase isolated from alkalophilic Bacillus sp. HJ-12, approximate Mw 42 kDa, was generally stable in the range of pH 6-10 and below 50$\circ$C and its highest activity was observed at 60$\circ$C with pH 7-9. The isolated $\beta $-1, 4-D-arabinogalactanase specifically hydrolyzed $\beta $-1, 4-galactosyl linkage that is the major structure of soybean arabinogalactan (SAG) but not $\beta $-1, 3-galactosyl linkage of the other polysaccharides. K. was estimated as 0.67 mg/ml by the method of Hanes-Woolf plot. No metals and chemical reagents inhibited the enzyme activity but urea did. The active site of this enzyme assumed to be tryptophan residue. The hydrolysis products from SAG, assayed by gel chromatography, TLC and HPLC, were predominantly galactotetraose (Gal$_{4}$) and triose (Gal$_{3}$) with a small portion. $\beta $-1, 4-D-arabinogalactanase hydrolyzed ONPG as well as SAG, and the degree of hydrolysis of SAG was 15% which is lower than that by the other $\beta $-1, 4-galactanases from different sources. SAG treated with this enzyme resulted in the reduction of specific viscosity up to 70%.