• Journal of Microbiology
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• v.44 no.4
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• pp.396-402
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• 2006

[ ${\beta}-Galactosidase$ ] is extensively employed in the manufacture of dairy products, including lactose-reduced milk. Here, we have isolated two gram-negative and rod-shaped coldadapted bacteria, BS 1 and HS 39. These strains were able to break down lactose at low temperatures. Although two isolates were found to grow well at $10^{\circ}C$, the BS 1 strain was unable to grow at $37^{\circ}C$. Another strain, HS-39, evidenced retarded growth at $37^{\circ}C$. The biochemical characteristics and the results of 16S rDNA sequencing identified the BS 1 isolate as Rahnella aquatilis, and showed that the HS 39 strain belonged to genus Buttiauxella. Whereas the R. aquatilis BS 1 strain generated maximal quantities of ${\beta}-galactosidase$ when incubated for 60h at $10^{\circ}C$, Buttiauxella sp. HS-39 generated ${\beta}-galactosidase$ earlier, and at slightly lower levels, than R. aquatilis BS 1. The optimum temperature for ${\beta}-galactosidase$ was $30^{\circ}C$ for R. aquatilis BS-1, and was $45^{\circ}C$ for Buttiauxella sp. HS-39, thereby indicating that R. aquatilis BS-1 was able to generate a cold-adaptive enzyme. These two cold-adapted strains, and most notably the ${\beta}-galactosidase$ from each isolate, might prove useful in some biotechnological applications.

• Korean Journal of Microbiology
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• v.43 no.3
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• pp.222-226
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• 2007

Proteases are degradative enzymes which hydrolyze a peptide bond between amino acids and they are abundantly applied to commercial field. In order to screen new source of pretense, bacteria secreting extracellular pretense were isolated by enrichment culture from deep sea water samples of East Sea, Korea. A bacterium, named as HJ19, showed the best growth and the largest clear zone in plates supplemented skim milk at $30^{\circ}C$. The partial DNA sequence analysis of the 16S rRNA gene, phenotypic tests and morphology identified that this strain was In genus Micrococcus. The strain HJ19 could not grow at $10^{\circ}C$ but it started growth and showed pretense activity at $20^{\circ}C$. The optimal growth was at $37^{\circ}C$ and the maximal protease activity at $30^{\circ}C$ was about 480unit/ml.

• Microbiology and Biotechnology Letters
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• v.19 no.5
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• pp.464-469
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• 1991

An $\alpha$-amylase producing bacterium, strain 2B, was isolated from soil and identified to genus Bacillus. To enhance $\alpha$-amylase productivity, strain 2B was mutagenized successively with nitrosoguanidine. For an efficient selection of a-amylase hyperproducers, mutants which produced $\alpha$-amylase in the presence of glucose were isolated. The resultant mutant HG4, which was classified as constitutive and catabolite derepressed hyperproducer of a-amylase, produced about 30 folds more $\alpha$-amylase than parental strain in medium containing lactose as carbon source. The strain HG4 grew rapidly and produced enzyme in parallel with cell growth. Moreover, its cell lysis did not occur until time of maximal yield of enzyme, which was considered to be a favorable characteristic for the production and purificiation of enzyme in industrial scale. The enzymatic properties of parental strain 2B and mutant strain HG4 were almost the same. The optimal temperature and pH for enzyme reaction was $70^{\circ}C$ and pH 6.0, respectively, in 'the presence of 0.6mM $Ca^[2+}$ as an effective stabilizer.

• Microbiology and Biotechnology Letters
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• v.38 no.4
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• pp.399-404
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• 2010

A hydrogen-producing bacterium (strain ES392) was isolated from pond water located in the Dong-Eui University, Busan, Korea. The cell was long-rod type ($1.4\;{\mu}m$) of about ($0.6\;{\mu}m$) in diameter, and not formed flagellum and spore. Phylogenetic analysis based on the 16S rRNA sequence and biochemical studies indicated that ES392 belonged to the genus Enterobacter sp. The optimum pH and temperature for hydrogen production was 7.5 and $35^{\circ}C$, respectively. The optimization of medium compositions which maximize hydrogen production from Enterobacter sp. ES392 was determined. As a result, the maximum hydrogen production was obtained under the conditions of 4% (w/v) sucrose, 0.5% (w/v) yeast extract and 50 mM potassium phosphate buffer (pH 7.5). Under batch culture conditions, the maximal hydrogen production and yield were obtained as 3481 mL/L and 1.33 mol/mol sucrose, respectively.

• Journal of Microbiology and Biotechnology
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• v.29 no.5
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• pp.765-775
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• 2019

A new ${\alpha}$-amylase-encoding gene (amySL3) of glycoside hydrolase (GH) family 13 was identified in soda lake isolate Alkalibacterium sp. SL3. The deduced AmySL3 shares high identities (82-98%) with putative ${\alpha}$-amylases from the genus Alkalibacterium, but has low identities (<53%) with functionally characterized counterparts. amySL3 was successfully expressed in Escherichia coli, and the recombinant enzyme (rAmySL3) was purified to electrophoretic homogeneity. The optimal temperature and pH of the activity of the purified rAmySL3 were determined to be $45^{\circ}C$ and pH 7.5, respectively. rAmySL3 was found to be extremely halophilic, showing maximal enzyme activity at a nearly saturated concentration of NaCl. Its thermostability was greatly enhanced in the presence of 4 M NaCl, and it was highly stable in 5 M NaCl. Moreover, the enzyme did not require calcium ions for activity, and was strongly resistant to a range of surfactants and hydrophobic organic solvents. The major hydrolysis products of rAmySL3 from soluble starch were maltobiose and maltotriose. The high ratio of acidic amino acids and highly negative electrostatic potential surface might account for the halophilic nature of AmySL3. The extremely halophilic, calcium-independent, and surfactant-resistant properties make AmySL3 a promising candidate enzyme for both basic research and industrial applications.

• Microbiology and Biotechnology Letters
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• v.44 no.4
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• pp.512-521
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• 2016

A bacterial strain was isolated from a soil sample collected on Jeju Island, Korea. The strain, designated WJ-2, exhibited a high xylanase activity, whereas cellulase activity was not detected. The 16S rRNA gene sequence of WJ-2 was highly similar to type strains of the genus Streptomyces. A neighbor-joining phylogenetic tree based on 16S rRNA gene sequences showed that strain WJ-2 is phylogenetically related to Streptomyces atrovirens. Furthermore, DNA-DNA hybridization analysis confirmed that strain WJ-2 is a novel subspecies of Streptomyces atrovirens. The genomic DNA G+C content was 73.98 mol% and the major fatty acid present was anteiso-C15:0 (36.19%). The growth and xylanase production of strain WJ-2 were significantly enhanced by using soytone and xylan as nitrogen and carbon sources, respectively. Crude enzyme preparations from the culture broth of strain WJ-2 exhibited maximal total xylanase activities at pH 7.0 and $55^{\circ}C$. Thin-layer chromatography analysis revealed that the crude enzyme degrades beechwood xylan to yield xylobiose and xylotriose as the principal hydrolyzed end products.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.219-225
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• 2006

Bacterial community structure in the Juam Reservoir was analysed using fluorescent in situ hybridization (FISH) technique from April 2005 to January 2006. Total bacterial numbers varied in the range of 1.58 ${\sim}\;2.73{\times}\;10^6\;cells\;mL^{-1}$ proportional to the concentration of chi-a and had the minimal value in January. The ratios of ${\alpha}\;{\cdot}\;{\beta}\;{\cdot}\;{\gamma}$-subclass proteobacteria and Cytophaga-Flavobacterium (CF) group to total bacteria ranged from 45.1% to 77.5%, and the ratios of ${\alpha}\;{\cdot}\;{\beta}\;{\cdot}\;{\gamma}$-subclasses to total bacteria in June and September with the concentration of chi-a measured were lower than those ratios in April and January. It suggests that enriched growth of Microcystis aeruginosa may inhibit the metabolic activlty of ${\alpha}\;{\cdot}\;{\beta}\;{\cdot}\;{\gamma}$-subclass proteobacteria. However, the ratio of CF group bacteria represented no large change depending on algal bloom. In terms of nitrifying bacteria, the numbers of ammonia-oxidizing bacteria ranged from 9.9 ${\times}\;10^4\;to\;25.5\;{\times}10^4\;cells\;mL^{-1}$ with sharp fluctuation whereas those of nitrite-oxidizing bacteria varied in 8.7${\sim}9.8{\times}10^4\;cells\;mL^{-1}$ without noticeable change except the maximal value of $20.3{\times}10^4\;cells\;mL^{-1}$ in January maybe due to the high DO.

• Korean Journal of Microbiology
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• v.32 no.4
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• pp.285-290
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• 1994

About 500 bacterial and fungal strains from a wide variety of natural habitats were screened for a new type II restriction endonuclease. Among the 500 species, we selected one species that produced a new restriction endonuclease. This strain has an optimum temperature of $30^{circ}C$ for growth. Morphological, cultural, and physiological characteristics were examined for identification of the isolated strain J-482. This strain was found to belong to the genus Alcaligenes. The restriction endonuclease was named as AspJI and partially purified from Alcaligenes sp. J-482 by DEAE-Sephadex A-50 column chromatography and gel filtration. Most of other nucleases were removed by the purification steps. The AspJI has a substrate specificity to ${lambda}$ DNA, pBR322 and Adenovirus-2 DNA. For its maximal activity, the isolated enzyme requires $MgCl_2$, which should be at least 12.5 mM and it does not need any other cofactors. It is maximally active in the absence of NaCl and is completely inactivated at 100 mM NaCl. The pH and temperature optima for activity were pH 7.5 and $37^{circ}C$, respectively. The DNA fragments generated by digesting ${lambda}$ DNA, pBR322, and Adenovirus-2 DNA with AspJI were the same as that produced by AatII. This suggests that AspJI is an isoschizomer of AatII.

• Journal of Life Science
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• v.32 no.4
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• pp.285-289
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• 2022

In this study, the growth characteristics of an agar-degrading bacterium isolated from seawater samples collected from Yeongheungdo, Incheon, and the characteristics of its agarase were analyzed. The 16S rRNA gene sequence of the isolated strain was 95% similar to that of the genus Agarivorans, and thus the isolated strain was named Agarivorans sp. HY-1. When Agarivorans sp. HY-1 was cultured in a marine broth 2216 medium at 27℃ and 250 rpm, it showed maximum growth on day 1 and showed maximum enzymatic activity on day 2. A crude enzyme solution was prepared from secreted agarase in the culture medium. The extracellular agarase of the Agarivorans sp. HY-1 strain showed maximal activity at 40℃ and pH 7.0 (20 mM Tris-HCl) with 591.91 U/l. The agarase exhibited relative activities of 64, 91, 100, 97, 89, and 60% at 20, 30, 40, 50, 60, and 70℃, respectively. At pH 5, 6, 7, and 8, the relative activities were 79, 95, 100, and 55%, respectively. Furthermore, the agarase exhibited >86% residual activity at 20, 30, and 40℃ for 2 hr and >44% residual activity at 50℃ after 2 hr. A TLC analysis confirmed that Agarivorans sp. HY-1 produced α-agarase. As the degradation products of α-agarase have anticancer and antioxidant effects, Agarivorans sp. HY-1 and its agarase may well prove useful.

• Korean Journal of Microbiology
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• v.52 no.2
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• pp.192-201
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• 2016

Recently, Psychrobacter sp. ArcL13 strain showing the extracellular lipase activity was isolated from the Chuckchi Sea of the Arctic Ocean. However, due to the low expression levels of the enzyme in the natural strain, the production of recombinant lipase is crucial for various applications. Identification of the gene for the enzyme is prerequisite for the production of the recombinant protein. Therefore, in the present study, a novel lipase gene (ArcL13-Lip) was isolated from Psychrobacter sp. ArcL13 strain by gene prospecting using PCR, and its complete nucleotide sequence was determined. Sequence analysis showed that ArcL13-Lip has high amino acid sequence similarity to lipases from bacteria of some Psychrobacter genus (84-90%) despite low nucleotide sequence similarity. The lipase gene was cloned into the bacterial expression plasmid and expressed in E. coli. SDS-PAGE analysis of the cells showed that ArcL13-Lip was expressed as inclusion bodies with a molecular mass of about 35 kDa. Refolding was achieved by diluting the unfolded protein into refolding buffers containing various additives, and the highest refolding efficiency was seen in the glucose-containing buffer. Refolded ArcL13-Lip showed high hydrolytic activity toward p-nitrophenyl caprylate and p-nitrophenyl decanoate among different p-nitrophenyl esters. Recombinant ArcL13-Lip displayed maximal activity at $40^{\circ}C$ and pH 8.0 with p-nitrophenyl caprylate as a substrate. Activity assays performed at various temperatures showed that ArcL13-Lip is a cold-active lipase with about 40% and 73% of enzymatic activity at $10^{\circ}C$ and $20^{\circ}C$, respectively, compared to its maximal activity at $40^{\circ}C$.