• Journal of Microbiology and Biotechnology
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• v.22 no.10
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• pp.1388-1394
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• 2012

A xylanase-producing thermophilic strain, Geobacillus sp. TC-W7, was isolated from a hot spring in Yongtai (Fuzhou, China). Subsequently, the xylanase gene that encoded 407 amino acids was cloned and expressed. The recombinant xylanase was purified by GST affinity chromatography and exhibited maximum activity at $75^{\circ}C$ and a pH of 8.2. The enzyme was active up to $95^{\circ}C$ and showed activity over a wide pH range of 5.2 to 10.2. Additionally, the recombinant xylanase showed high thermostability and pH stability. More than 85% of the enzyme's activity was retained after incubation at $70^{\circ}C$ for 90 min at a pH of 8.2. The activity of the recombinant xylanase was enhanced by treatment with 10 mM enzyme inhibitors (DDT, Tween-20, 2-Me, or TritonX-100) and was inhibited by EDTA or PMSF. Its functionality was stable in the presence of $Li^+$, $Na^+$, and $K^+$, but inhibited by $Hg^{2+}$, $Ni^{2+}$, $Co^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Pb^{2+}$, $Fe^{3+}$, and $Al^{3+}$. The functionality of the crude xylanase had similar properties to the recombinant xylanase except for when it was treated with $Al^{2+}$ or $Fe^{2+}$. The enzyme might be a promising candidate for various industrial applications such as the biofuel, food, and paper and pulp industries.

• Journal of Microbiology and Biotechnology
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• v.31 no.3
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• pp.483-491
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• 2021

Two putative genes, lip29 and est29, encoding lipolytic enzymes from the thermophilic bacterium Geobacillus thermocatenulatus KCTC 3921 were cloned and overexpressed in Escherichia coli. The recombinant Lip29 and Est29 were purified 67.3-fold to homogeneity with specific activity of 2.27 U/mg and recovery of 5.8% and 14.4-fold with specific activity of 0.92 U/mg and recovery of 1.3%, respectively. The molecular mass of each purified enzyme was estimated to be 29 kDa by SDS-PAGE. The alignment analysis of amino acid sequences revealed that both enzymes belonged to GDSL lipase/esterase family including conserved blocks with SGNH catalytic residues which was mainly identified in plants before. While Est29 showed high specificity toward short-chain fatty acids (C4-C8), Lip29 showed strong lipolytic activity to long-chain fatty acids (C12-C16). The optimal activity of Lip29 toward p-nitrophenyl palmitate as a substrate was observed at 50℃ and pH 9.5, respectively, and its activity was maintained more than 24 h at optimal temperatures, indicating that Lip29 was thermostable. Lip29 exhibited high tolerance against detergents and metal ions. The homology modeling and substrate docking revealed that the long-chain substrates showed the greatest binding affinity toward enzyme. Based on the biochemical and insilico analyses, we present for the first time a GDSL-type lipase in the thermophilic bacteria group.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.495-495
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• 2005

• Journal of Microbiology and Biotechnology
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• v.18 no.4
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• pp.611-615
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• 2008

Novel groups of uncultivable anaerobic thermophiles were isolated from compost by enrichment cultivation in medium with a cell-free extract of Geobacillus toebii. The cell-free extract of G. toebii provided the medium with growth-supporting factors (GSF) needed to cultivate the previously uncultured microorganisms. Twenty-nine GSF-requiring candidates were successfully cultivated, and 16 isolated novel bacterial strains were classified into three different groups of uncultivable bacteria. The similarity among these 16 isolates and a phylogenetic analysis using 16S rRNA gene sequences revealed that these GSF-requiring strains represented novel groups within the family Clostridiaceae.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.12
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• pp.509-514
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• 2016

From the point of view to prevent airborne infection-related diseases such as H1N1, SARS, and MERS, an actual application of air cleaning and purification systems including technologies like UVGI has become increasingly important. Recently, an air purification system using REME (Reflective Electro Magnetic Energy) developed in the U.S. is applied for indoor air purification and sterilization technology to counteract the outbreak of new airborne infections. In this study, an air sterilization performance experiment using REME was carried out. The results verified that air sterilization performance in the case of installing a REME system in a medical center was 31%, namely the number of floating bacteria decreased by 31% after only a five-day operation. In addition, the number of culture collections in the REME operating air conditioning systems using nonpathogenic Geobacillus stearothemophilus as a biological indicator decreased maximally to 67%. A field application of REME technology will be useful to prevent airborne infection-related diseases, especially in response to public health crises due to the advent of emerging diseases.

• Korean Journal of Food Science and Technology
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• v.42 no.3
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• pp.361-367
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• 2010

Bacterial contamination of cooked rice was analyzed to evaluate the microbial safety. Thirty raw rice samples were collected in Korea and cooked in an electric rice cooker. Mesophilic aerobe, food-poisoning Bacillus cereus group, and their toxin genes were determined on cooked rice. The percentage of total mesophilic aerobe based on 1-3 log CFU/g was 27% among the samples. Bacillus spp. in MYP selective medium was similar to the number of mesophilic aerobe, whileas Bacillus spp. was detected in most samples after enrichment. Thirty-seven isolates from 30 cooked rices were identified as B. thuringiensis, B. cereus, B. valismortis, B. pumilus, B. coagulans, B. licheniformis, Geobacillus stearothermophilus, and Brevibacillus laterosporus. Twenty isolates (54%), more than half of the isolates, were B. thuringiensis while nine (27%) were identified as B. cereus. All B. thuringiensis isolates possessed non-hemolytic toxin genes and interestingly, seven B. cereus among nine isolates possessed emetic toxin genes. More B. thuringiensis was present on the cooked rice than B. cereus and most B. cereus possessed emetic toxin genes rather than diarrheal toxin genes. Therefore, food-borne outbreak due to B.cereus on the cooked rice kept at room temperature might be examples of emetic food-poisoning.

• Proceedings of the Microbiological Society of Korea Conference
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• 2001.11a
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• pp.46-53
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• 2001

A commensal thermophile, Symbiobacterium toebii, isolated from hay compost (toebii) in Korea commensally interacted with a thermophilic Geobacillus toebii sp. nov., which was a new species within the genus Geobacillus on the basis of the phenotypic traits and molecular systematic data. S. toebii required the crude extracts and/or culture supernatant of the Geobacillus toebii for axenic growth and could grow on the temperature between 45 and $70^{\circ}C$ (optimum: $60^{\circ}C$; 2.4 h doubling time) and pH 6.0 and 9.0 (optimum: pH 7.5). The G+C content of the genomic DNA was $65 mol\%$, and the major quinones were MK-6 and MK-7. A phylogenetic analysis of its 16S rDNA sequence indicated that Symbiobacterium toebii was closely related with solely reported Symbiobacterium thermophilum. The presence of the commensal thermophile 16S rDNA and accumulation of indole in all the enriched cultures indicate that Symbiobacterium toebii is widely distributed in the various soils. The genome of S. toebii constituted a circular chromosome of 3,280,275 base pairs and there was not an extra-chromosomal element (ECE). It contained about 4,107 predicted coding sequences. Of these protein coding genes, about $45.6\%$ was encoded well-known proteins and annotated the functional assignment of 1,874 open reading frames (ORFs), and the rest predicted to have unknown functions. The genes encoding thermostable tyrosine phenol-lyase and tryptophan indole-lyase were cloned from the genomic DNA of S. toebii and the enzymatic production of L-tyrosine and L-tryptophan was carried out with two thermostable enzymes overexpressed in recombinant E. coli.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2005.06a
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• pp.283-284
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• 2005

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.185.4-185
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• 2005

• Microbiology and Biotechnology Letters
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• v.36 no.4
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• pp.360-365
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• 2008

For the screening of residual antibiotics in foods, bioassays and microbiological inhibitor tests are commonly applied. These methods are tested by the various susceptibility of bacteria against different kinds of antibiotics. However, the sensitivity of bioassay is generally insufficient to detect some residual antibiotics at level of interest. This study was performed to investigate the detection limit of variable antibiotics of the bioassay and to improve the sensitivity to some antibiotics. The sensitivity of bioassay using Bacillus megaterium ATCC 9885, B. subtilis ATCC 6633, B. cereus ATCC 11778 and Geobacillus stearothermophilus ATCC 10149 was low in the detection of macrolides, quinolones, chloramphenicol, and monensin. On the contrary, Micrococcus luteus ATCC 9341 showed high sensitivity to macrolides and Escherichia coli ATCC 11303 was highly sensitive to quinolones and aminoglycosides. Consequently, both strains would be useful to improve sensitivity of bioassay with a wide detection range.