• Journal of Microbiology and Biotechnology
• /
• v.16 no.4
• /
• pp.633-636
• /
• 2006

The purpose of this study was to measure the heat resistance and core mineral content of Geobacillus stearothermophilus ATCC 7953 spores when the sporulating cells were exposed to heat shock at different times during sporulation. Heat shock during sporulation was found to increase the heat resistance of the spores produced subsequently. The spores heat shocked 2 h after the end of the exponential phase showed the highest heat resistance and a 3D-fold increase in the $d_{10}$ compared with the non-heat-shocked spores. The enhanced heat resistance was likely due to the increased mineral content observed in the spores heat shocked at $t_7\;or\;t_8$.

• Journal of Microbiology and Biotechnology
• /
• v.18 no.3
• /
• pp.490-496
• /
• 2008

Symbiobacterium toebii is a commensal symbiotic thermophile that cannot grow without support from a partner bacterium. We investigated the properties of Symbiobacterium growth-supporting factors (SGSFs) produced by the partner bacterium Geobacillus toebii. SGSFs occurred in both the cell-free extract (CFE) and culture supernatant of G. toebii and might comprise multifarious materials because of their different biological properties. The heavy SGSF contained in the cytosolic component exhibited heat- and proteinase-sensitive proteinaceous properties and had a molecular mass of >50 kDa. In contrast, the light SGSF contained in the extracellular component exhibited heat-stable, proteinase-resistant, nonprotein properties and had a molecular mass of <10 kDa. Under morphological examination using light microscopy, S. toebii cultured with the culture supernatant of G. toebii was filamentous, whereas S. toebii cultured with the CFE of G. toebii was rod-shaped. These results strongly suggest that the SGSFs produced by G. toebii comprise two or more types that differ in their growth-supporting mechanisms, although all support the growth of S. toebii. Upon the examination of the distribution of SGSFs in other bacteria, both cytosolic and extracellular components of Geobacillus kaustophilus, Escherichia coli, and Bacillus subtilis had detectable growth-supporting effects for S. toebii, indicating that common SGSF materials are widely present in various bacterial strains.

• Journal of Microbiology and Biotechnology
• /
• v.14 no.2
• /
• pp.312-316
• /
• 2004

Five strains, producing bacterial thermostable L-arabinose isomerase, were isolated from Korean soil samples obtained from compost under high temperature circumstances. Among these strains, the CBG-Al showed the highest L-arabinose isomerase activity at $60^\circ{C}$ and was selected as a D-tagatose producing strain from D-galactose. This strain was identified as Geobacillus thermodenitrificans based on the 16S rRNA analysis, and biological and biochemical characteristics. The isolated strain was aerobic, rod-shaped, Gram-positive, nonmotile, and an endospore-forming bacterium. No growth was detected in culture temperature below $40^\circ{C}$. The maximum growth temperature and maximum temperature of enzyme activity were $75^\circ{C}$ and $65^\circ{C}$, respectively. In metal ion effects, $Ca^{2+}$ was the most effective enzyme activator with the reaction rate by 150%. In a 5-1 jar fermentor with 3-1 MY medium, L-arabinose isomerase activity was growth-associated and pH decreased rapidly after the initial logarithmic phase.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.16 no.4
• /
• pp.560-565
• /
• 2013

Biological decontamination means the removal of microorganisms from the inanimate object such as building or equipment. In this study, hydrogen peroxide vapor efficacy test using VHP 1000ED system(Steris LifeSciences) were conducted for G. stearothermophilus spore with agent materials(aluminum, stainless steel, poly-carbonate, viton, silicone, kapton and glass). Total recovered spores exposed to hydrogen peroxide vapor(1.0 g/min) during 7, 15, 30, 60 min were calculated. As a result, all agent materials were totally decontaminated within 60 min at 1.0 g/min concentration with 35% hydrogen peroxide vapor. Finally, we could confirmed that hydrogen peroxide vapor possess sporicidal capacity of G. stearothermophilus and found the optimum decontamination conditions with VHP1000ED system.

• Korean Journal of Microbiology
• /
• v.45 no.1
• /
• pp.32-40
• /
• 2009

To understand contribution of thermophilic microorganisms in decomposition of litter deposits on shore of lakes, we surveyed a lakeshore litter deposit for bacteria growing at $60^{\circ}C$. Ten thermophilic isolates were selected for in-depth characterization, based on their high capacity to degrade high molecular weight organic compounds. Based on phylogenetic analysis on their 16S rRNA gene sequences, all isolates were identified as Geobacillus. The optimal growth temperature and pH of the strains ranged $55{\sim}60^{\circ}C$ and 6.0${\sim}$8.0, respectively. Salinity was inhibitory to the growth of the isolates, showing marked decrease of growth rates at 3% salinity. Based on activities of hydrolytic enzymes and profiles of carbohydrate utilization (determined by API 50 CHB kit), three G. stearothermophilus strains showed patterns clearly distinctive from other isolates. Two G. kaustophilus strains also demonstrated distinctiveness in their metabolic pattern and ecological parameters. However, ecological and metabolic profiles of the other five isolates were more variable and showed some degree of digression from their phylogenetic classification. Therefore, it could be concluded that endospore-forming thermophilic bacteria in lakeshore litter deposits contribute to degradation of organic materials with diverse ecological niches while having successions similar to microbial flora in compost. We propose that the thermophilic isolates and/or their thermo-tolerant enzymes can be applied to industrial processes as appropriate mixtures.

• Journal of Food Hygiene and Safety
• /
• v.38 no.5
• /
• pp.356-360
• /
• 2023

We analyzed the heat resistance of non-pathogenic Bacillus atrophaeus, Bacillus subtilis, and Geobacillus stearothermophilus spores which exhibit strong heat resistance and evaluated the possibility of using them to determine direct sterilization when manufacturing retort foods. The D₁₂₁-values of B. subtilis, G. stearothermophilus, and B. atrophaeus spores were 2.9±0.1 min, 4.3±0.1 min, and 3.7±0.1 min, respectively. The Z-values of B. subtilis, G. stearothermophilus, and B. atrophaeus spores were 43.0±1.4℃, 25.0±1.6℃, and 35.8±1.4℃, respectively. The D₁₂₁-values of B. subtilis, G. stearothermophilus, and B. atrophaeus spores were all higher than that of Clostridium botulinum spores used to confirm retort food sterilization. Considering these results, B. subtilis, G. stearothermophilus, and B. atrophaeus spores can be used instead of the pathogenic spore-forming bacteria C. botulinum when sterilizing retort food. In addition, sterilization can be confirmed in 2 to 3 days, a shorter time than the 13 days required for existing bacterial growth experiments based on the Korean food code.

• Asian-Australasian Journal of Animal Sciences
• /
• v.26 no.11
• /
• pp.1651-1658
• /
• 2013

Nitrate contamination in ground and surface water is an increasingly serious environmental problem and only a few bacterial strains have been identified that have the ability to remove nitrogen pollutants from wastewater under thermophilic conditions. We therefore isolated thermophilic facultative bacterial strains from wood chips that had been composted with swine manure under aerated high temperature conditions so as to identify strains with denitrifying ability. Nine different colonies were screened and 3 long rod-shaped bacterial strains designated as SG-01, SG-02, and SG-03 were selected. The strain SG-01 could be differentiated from SG-02 and SG-03 on the basis of the method that it used for sugar utilization. The 16S rRNA genes of this strain also had high sequence similarity with Geobacillus thermodenitrificans $465^T$ (99.6%). The optimal growth temperatures ($55^{\circ}C$), pH values (pH 7.0), and NaCl concentrations (1%) required for the growth of strain SG-01 were established. This strain reduced 1.18 mM nitrate and 1.45 mM nitrite in LB broth after 48 h of incubation. These results suggest that the G. thermodenitrificans SG-01 strain may be useful in the removal of nitrates and nitrites from wastewater generated as a result of livestock farming.

• Journal of Microbiology and Biotechnology
• /
• v.25 no.7
• /
• pp.1070-1083
• /
• 2015

A gene (GT-SM3B) encoding a thermostable secreted oligoendopeptidase (GT-SM3B) was cloned from the thermophile Geobacillus thermoleovorans DSM 15325. GT-SM3B is 1,857 bp in length and encodes a single-domain protein of 618 amino acids with a 23-residue signal peptide having a calculated mass of 67.7 kDa after signal cleavage. The deduced amino acid sequence of GT-SM3B contains a conservative zinc metallopeptidase motif (His⁴⁰⁰-Glu⁴⁰¹-X-XHis⁴⁰⁴). The described oligopeptidase belongs to the M3B subfamily of metallopeptidases and displays the highest amino acid sequence identity (40.3%) to the oligopeptidase PepF_Ba from mesophilic Bacillus amyloliquefaciens 23-7A among the characterized oligopeptidases. Secretory production of GT-SM3B was used, exploiting successful oligopeptidase signal peptide recognition by Escherichia coli BL21 (DE3). The recombinant enzyme was purified from the culture fluid. Homodimerization of GT-SM3B was determined by SDS-PAGE. Both the homodimer and monomer were catalytically active within a pH range of 5.0–8.0, at pH 7.3 and 40℃, showing the K_m, V_max, and k_cat values for carbobenzoxy-Gly-Pro-Gly-Gly-Pro-Ala-OH peptidolysis to be 2.17 ± 0.04 × 10^-6 M, 2.65 ± 0.03 × 10^-3 µM/min, and 5.99 ± 0.07 s^-1, respectively. Peptidase remained stable at a broad pH range of 5.0–8.0. GT-SM3B was thermoactive, demonstrating 84% and 64% of maximum activity at 50℃ and 60℃, respectively. The recombinant oligopeptidase is one of the most thermostable M3B peptidase, retaining 71% residual activity after incubation at 60℃ for 1 h. GT-SM3B was shown to hydrolyze a collagenous peptide mixture derived from various types of collagen, but less preferentially than synthetic hexapeptide. This study is the first report on an extracellular thermostable metallo-oligopeptidase.

• Korean Journal of Environmental Biology
• /
• v.25 no.3
• /
• pp.260-266
• /
• 2007

A thermophilic bacterium capable of poly (L-lactide)(PLLA) degradation was isolated from cultivating soil in Korea. The isolate was Gram positive rod-shaped bacterium, and was identified as Geobacillus caldoxylosilyticus based on the 16S rDNA sequence analysis. The strain proved to be a new PLLA degrading bacterium which has not been reported in the open literatures yet. The degradation activity of the strain was assessed in a sterilized compost inoculated with the strain under controlled compost condition at $58^{\circ}C$ for 40 days. The strain mineralized 66%, 57%, 41% and 40% of PLLA5000, PLLA11000, PLLA34000 and PLLA256000 whose weight average molecular weights were 5000, 11000, 34000 and 256000, respectively. Incorporation of 0.1% each of gelatin, yeast extract and ammonium sulfate in the compost containing PLLA256000 as a nutritional supplement raised the biodegradation activity by 27%, 13% and 10%, respectively. Increase of the inoculum size from $10^9cfu\;g^{-1}\;to\;10^{10}cfu\;g^{-1}\;and\;10^{11}cfu\;g^{-1}$ also enhanced the biodegradation activity by 14% and 20%, respectively.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.19 no.5
• /
• pp.669-674
• /
• 2016

The purpose of this study is to demonstrate the suitability of hydrogen peroxide($H_2O_2$) vapor system for platform interior decontamination. Geobacillus stearothermophilus biological indicator(BI) strips and a field tent were used as a biological simulant and as a simulated platform, respectively. Decontamination was performed based on injection rates and tent sizes with exposure time 60 minutes. We standardized the conditions for the field tent decontamination : 8.0 g/min for $30m^3$($H_2O_2$ vapor concentration of 150~500 ppm, relative humidity of 50 %) and 12.0 g/min for $60m^3$($H_2O_2$ vapor concentration of 250~400 ppm, relative humidity of 55 %). Thus we suggest the system is one of the possible candidates for decontamination of platform interiors.