• Journal of Microbiology and Biotechnology
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• v.17 no.4
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• pp.604-610
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• 2007

A psychrotrophic strain 7195 showing extracellular lipolytic activity towards tributyrin was isolated from deep-sea sediment of Prydz Bay and identified as a Psychrobacter species. By screening a genomic DNA library of Psychrobacter sp. 7195, an open reading frame of 954 bp coding for a lipase gene, lipA1, was identified, cloned, and sequenced. The deduced LipA1 consisted of 317 amino acids with a molecular mass of 35,210 kDa. It had one consensus motif, G-N-S-M-G (GXSXG), containing the putative active-site serine, which was conserved in other cold-adapted lipolytic enzymes. The recombinant LipA1 was purified by column chromatography with DEAE Sepharose CL-4B, and Sephadex G-75, and preparative polyacrylamide gel electrophoresis, in sequence. The purified enzyme showed highest activity at $30^{\circ}C$, and was unstable at temperatures higher than $30^{\circ}C$, indicating that it was a typical cold-adapted enzyme. The optimal pH for activity was 9.0, and the enzyme was stable between pH 7.0-10.0 after 24h incubation at $4^{\circ}C$. The addition of $Ca^{2+}\;and\;Mg^{2+}$ enhanced the enzyme activity of LipA1, whereas the $Cd^{2+},\;Zn^{2+},\;CO^{2+},\;Fe^{3+},\;Hg^{2+},\;Fe^{2+},\;Rb^{2+}$, and EDTA strongly inhibited the activity. The LipA1 was activated by various detergents, such as Triton X-100, Tween 80, Tween 40, Span 60, Span 40, CHAPS, and SDS, and showed better resistance towards them. Substrate specificity analysis showed that there was a preference for trimyristin and p-nitrophenyl myristate $(C_{14}\;acyl\; groups)$.

• Korean Journal of Food Science and Technology
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• v.34 no.6
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• pp.1085-1090
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• 2002

Leuconostoc mesenteroides, the major bacterium in the initial phase of lactate-fermentation in kimchi, produces lactic acid, acetic acid, mannitol, and $CO_2$. It also secrets dextransucrase, which catalyzes the transfer reaction of glucose from sucrose to maltose, synthesizing mainly panose ($6^_2-{\alpha}-D-glucopyranosylmaltose)$, a probiotic oligosaccharide. To use the strain as a starer culture to produce high amount of panose during kimchi fermentation, we screened psychrotrophic strains showing fast growth rate at low temperature among the isolates of Leuconostoc sp. and selected two strains showing high dextransucrase activity. The strains were identified as Leuconostoc mesenteroides, which can be used as function added-starters for lactate-fermented foods.

• Microbiology and Biotechnology Letters
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• v.35 no.2
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• pp.135-141
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• 2007

To increase the consumer acceptability of yam and the shelf-life of fresh-cut yam, organic acid-treated fresh-cut yam was prepared. When uncontaminated fresh-cut yam was stored at $4^{\circ}C$ for 14 days after treatment with 1% (v/w) organic acids, the browning and microbial putrefaction of fresh-cut yam were inhibited by treatment of acetic acid or maleic acid, whereas treatment of citric acid and ascorbic acid, commonly used browning inhibitors in food industry, did not show apparent effects on the browning and putrefaction of yam. The Inhibitory effects of acetic acid or maleic acid were superior than those of NaOCl (100 ppm), hydrogen peroxide (100 ppm) or commercially available washing solution. Also, treatments of 1% acetic acid, or 1% maleic acid Into artificially-contaminated yam $(10^5\;CFU/g-yam)$ showed strong inhibition of browning and putrefaction during long term storage at $4^{\circ}C$. The growth inhibition test indicated that 0.1% is enough to inhibit the growth of psychrotrophic yam-putrefactive Pseudomonas sp., and treatment of 0.1% acetic acid, or 0.1% maleic acid inhibited the browning and microbial putrefaction of fresh-cut yam. Our results suggested long-term distribution of yam or other root crops products is possible by treatment of organic acid, such as acetic acid, combined with aseptic vacuum packaging technology.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.383-389
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• 1991

In order to produce alkaline protease, psychrotrophic bacterium which have high enzyme activity at low temperature, was isolated by using enrichment culture from various samples and identified as genus alkalopsychrotropic Pseudomonas sp. RP-222. The optimal culture conditions for enzyme production were pH- 10.0, temperature-$20^{\circ}C$ and culture time-4 days. The optimum pH and temperature for the enzyme activity were pH 10.5 and $40^{\circ}C$, respectively and the enzyme was relatively stable at pH 7.0~13.0 and below $50^{\circ}C$. The enzyme was inhibited by ethylenediaminetetraacetate and phenylmethylsulfonylfluoride, indicating that the enzyme was a serine metalloenzyme, but considerably stable in the presence of surface active agents. Activity of the enzyme was increased by the addition of 0.05% Na-$\alpha$-olefin sulfonate.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.1
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• pp.23-29
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• 1977

Three kinds of samples, Trachpenalus curiviostris, Astroconger myriaster and Cantherines modestus which were pre-treated in a processing plant were frozen at $-40^{\circ}C$ in a contact freezer and stored for 32 days.The numbers of general bacterium, coliforms and E. coli were measured at 8 day intevals during frozen storage and the isolated strains was classified. The results are as follows; 1. The numbers of coliforms and E. coli in the samples before freezing were much higher, than those during frozen storage and it tended to decrease. 2. General bacteria showed little change in number before and after being frozen. Among 97 strains of isolated coliforms, only 4 strains of K. aerogenes I ana 4 strains of K, cloacae were classified and the rest was not determined. 3. Ninety percent of coliforms was found to be psychrotrophic coliforms, which were able to grow at $5^{\circ}C$ within a week. 4. Vibrio and Pseudomonas were superior in number before freezing while Flavobacterium cytophaga and Moraxella were superior during frozem storage.

• Applied Biological Chemistry
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• v.44 no.4
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• pp.246-250
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• 2001

In order to produce alkaline protease, psychrotrophic Bacterium which have high enzyme activity, was isolated by using enrichment culture from soil samples and identified as genus Bacillus sp. The optimal pH and temperature for the enzyme activity were pH 6 and $40^{\circ}C$. The temperature range of high enzyme activity was $20{\sim}40^{\circ}C$. The optimal initial pH of culture condition for enzyme was pH 6. The most favorable carbon and nitrogen sources for the production of protease by Bacillus sp. WRD-2 were 3% maltose and 4% yeast extract, respectively.

• Journal of Microbiology and Biotechnology
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• v.21 no.3
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• pp.236-242
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• 2011

A psychrotrophic bacterium, Arthrobacter sp. ON14, isolated from Antarctica, was shown to exhibit a high ${\beta}$-galactosidase activity at a low temperature. A genomic library of ON14 was constructed and screened for ${\beta}$-galactosidase genes on functional plates containing 5-bromo-4-chloro-3-indolyl-${\beta}$-D-galactopyranoside (X-gal) as the substrate. Two different ${\beta}$-galactosidase genes, named as galA, galB, were found in ON14. Computational analyses of the genes revealed that the encoded protein GalA belongs to family 2 of glycosyl hydrolysases and is a cold-active protein, whereas GalB belongs to family 42 of glycosyl hydrolysases and is a mesophilic protein. Reverse transcription analyses revealed that the expression of galA is highly induced at a low temperature ($4^{\circ}C$ ) and repressed at a high temperature ($28^{\circ}C$ ) when lactose is used as the sole carbon source. Conversely, the expression of galB is inhibited at a low temperature and induced at a high temperature. The purified GalA showed its peak activity at $15^{\circ}C$ and pH 8. The mineral ions $Na^+$, $K^+$, $Mg^{2+}$, and $Mn^{2+}$ were identified as enzyme activators, whereas $Ca^{2+}$ had no influence on the enzyme activity. An enzyme stability assay revealed that the activity of GalA is significantly decreased when it is incubated at $45^{\circ}C$ for 2 h, and all its activity is lost when it is incubated at $50^{\circ}C$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.184-190
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• 1984

Sardine, Sardinops melanosticta, has been caught more than fifty thousand metric tons every year in adjacent sea of Korea, but most of them used for uneatable fish meal because of their rapid spoilage. Usually it is known that the main reason of putrefaction of foods is caused by the maicro-organisms included in them. Therefore, this experiment was carried out to identify the micro-organisms isolated from the intestine of fresh sardine and characterize their proteolytic enzymes produced from them. Aerobic cell count ranged from $1.7{\times}10^4\;to\;3.6{\times}10^5/g$, while anaerobic cell count, from $2.9{\times}10^4\;to\;5.5{\times}10^5/g$. Most of the isolated strains were psychrotrophic mesophiles. Among the two hundred and eighty strains isolated from the fresh samples, fifty-six strains ($20.0\%$) were proteolytics, one hundred and seventy-five strains ($62.5\%$) were lipolytics and tenty-nine strains ($10.5\%$) had the ability to produce hydrogn sulfide. The most predominantly isolated microbial groups from the fresh sardine were Moraxella ($31.4\%$) and Pseudomonas sup. ($28.6\%$). Flavobacterium-Cytophaga, Vibrio, Acinetobacter, Micrococcus spp. and Enterobacteriaceae appeared from $7.9\%\;to\;5\%$ out of total tested strains. The average bacterial count in the spoiled samples (stored at about $18^{\circ}C$ for 48 hours) was increased to the level of $2.9{\times}10^8/g$ for aerobes, $1.5{\times}10^8/g$ for anaerobes, then one hundred and ten strains, corresponding to $52\%$, out of two hundred and thirteen strains submitted to the test were proteolytics. The strongest proteolytic bacterium among the two hundred and eighty strains was identified as Pseudomonas 101 which grew best at $25^{\circ}C$. The optimum condition for the activity of the proteolytic enzyme produced by Pseudomonas 101 appeared $35^{\circ}C$ and pH 9.0, but the activity was relatively unchanged between 5.0 and 11.0 of pH and between $30^{\circ}C\;and\;50^{\circ}C$ of temperature.