• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.353-360
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• 1998

A bacterial strain PN33 producing large amounts of extracellular pectin lyase (PNL, EC 4.2.2.10) was isolated from soil. The isolated bacterium was identified as a strain of Bacillus sp. Production of PNL by the strain was induced only by pectins, with a higher degree of esterification, which had been added to the culture medium as a sole carbon source. The optimal medium for PNL production was determined to consist of 10 g pectin, 2 g yeast extract, 4 g $K_2HPO_4{\cdot}3H_2O$, 0.6 g $MgSO_4$, and 0.11 g $CaCl_2$ per liter (pH 7.0). The PNL activity in the culture supernatant reached the highest level of 132 mU/ml after 32 h cultivation at $37^{\circ}C$ in the optimal medium. The PNL produced was purified to homogeneity by ammonium sulfate fractionation (50~80%), and cation exchange and size exclusion chromatographies. The molecular mass of the enzyme was estimated to be approximately 52 kDa by SDS-PAGE. Almost the same mass was determined by nondenaturing PAGE, indicating that the functional enzyme had a monomeric structure. As expected, the PNL exhibited higher activities on the highly esterified pectins whereas it gave no detectable activity on polygalacturonic acid. The enzyme showed the highest activity at the acidic pH of 6.0, exceptional for a bacterial PNL. Maximum activity was measured at $40^{\circ}C$, although the stability f the purified enzyme was poor at this temperature. alcium (1 mM) was found to activate the PNL activity by $50\%$, and also remarkably increased the thermal stability f the enzyme. Phenylmethylsulfonylfluoride (PMSF) and iethylpyrocarbonate (DEPC) inhibited the PNL activity lmost completely at the concentration of 5 mM. This result ndicates that some serine and histidine residues of the nzyme may play an essential role for catalytic function of he enzyme.

• Journal of Ginseng Research
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• v.40 no.2
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• pp.105-112
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• 2016

Background: Minor saponins or human intestinal bacterial metabolites, such as ginsenosides Rg3, F2, Rh2, and compound K, are more pharmacologically active than major saponins, such as ginsenosides Rb1, Rb2, and Rc. In this work, enzymatic hydrolysis of ginsenoside Rb1 was studied using enzyme preparations from cultured mycelia of mushrooms. Methods: Mycelia of Armillaria mellea, Ganoderma lucidum, Phellinus linteus, Elfvingia applanata, and Pleurotus ostreatus were cultivated in liquid media at $25^{\circ}C$ for 2 wk. Enzyme preparations from cultured mycelia of five mushrooms were obtained by mycelia separation from cultured broth, enzyme extraction, ammonium sulfate (30-80%) precipitation, dialysis, and freeze drying, respectively. The enzyme preparations were used for enzymatic hydrolysis of ginsenoside Rb1. Results: Among the mushrooms used in this study, the enzyme preparation from cultured mycelia of A. mellea (AMMEP) was found to convert ginsenoside Rb1 into compound K with a high yield, while those from G. lucidum, P. linteus, E. applanata, and P. ostreatus produced remarkable amounts of ginsenoside Rd from ginsenoside Rb1. The enzymatic hydrolysis pathway of ginsenoside Rb1 by AMMEP was $Rb1{\rightarrow}Rd{\rightarrow}F2{\rightarrow}$ compound K. The optimum reaction conditions for compound K formation from ginsenoside Rb1 were as follows: reaction time 72-96 h, pH 4.0-4.5, and temperature $45-55^{\circ}C$. Conclusion: AMMEP can be used to produce the human intestinal bacterial metabolite, compound K, from ginsenoside Rb1 with a high yield and without food safety issues.

• Applied Biological Chemistry
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• v.13 no.1
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• pp.87-92
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• 1970

Sericin hydrolyzing enzyme, produced by the selected bacteria, S4-1-1, was studied and following properties were obtained. 1. The activity of this bacterial sericinase was not decreased for 30 days of storage at $5^{\circ}C$. But at $20^{\circ}C$, for 30 hrs. was the maximum period to keep the initial activity of this enzyme. 2. This bacterial enzyme gave only sericinase activity but never indicated fibroin hydrolyzing activity. 3. The chelating reagent of EDTA and Ag or Hg ions were classified as strung inhibitors but Cu and Cd ions were indicated as moderate inhibitors to this enzyme action. 4. This enzyme was not inhibited by the surface active agent, Peretex-N, but strongly activated by this agent at low concentration. In the other hand, by the application of this enzyme to the unwinding works on the mulberry cocoon, the following results were also obtained. 1. On the weight and length, nonbreaking Length, size, colour and unwinding ratio of have, the enzyme appling method was superior to generally used cooking method. 2. The tested results of strength and elongation, bouchon, haririness loops, neatness and evenness of have were also indicated spuerior properties.

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1518-1521
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• 2008

Bacteria sense their population density and coordinate the expression of target genes, including virulence factors in Gram-negative bacteria, by the N-acylhomoserine lactones (AHLs)-dependent quorum sensing (QS) mechanism. In contrast, several soil bacteria are able to interfere with QS by enzymatic degradation of AHLs, referred to as quorum quenching. A potent AHL-degrading enzyme, AiiA, from Bacillus thuringiensis has been reported to effectively attenuate the virulence of bacteria by quorum quenching. However, little is known about the role of AiiA in B. thuringiensis itself. In the present study, an aiiA-defective mutant was generated to investigate the role of AHA in rhizosphere competence in the root system of pepper. The aiiA mutant showed no detectable AHL￢-egrading activity and was less effective for suppression of soft-rot symptom caused by Erwinia carotovora on the potato slice. On the pepper root, the survival rate of the aiiA mutant significantly decreased over time compared with that of wild type. Interestingly, viable cell count analysis revealed that the bacterial number and composition of E. carotovora were not different between treatments of wild type and the aiiA mutant. These results provide evidence that AHA can play an important role in rhizosphere competentce of B. thuringiensis and bacterial quorum quenching to Gram-negative bacteria without changing bacterial number or composition.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.732-737
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• 2015

We present here an in silico search of fungal sterol-esterase/lipase and bacterial depolymerase sequences from environmental metagenomes. Both enzyme types contain the α/β-hydrolase protein fold. Analysis of DNA conserved motifs, protein homology search, phylogenetic analysis, and protein 3D modeling have been used, and the efficiency of these screening strategies is discussed. The presence of bacterial genes in the metagenomes was higher than those from fungi, and the sequencing depth of the metagenomes seemed to be crucial to allow finding enough diversity of enzyme sequences. As a result, a novel putative PHA-depolymerase is described.

• Journal of Microbiology and Biotechnology
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• v.11 no.1
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• pp.35-39
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• 2001

A simple method for studying the lectin-like interactions between Helicobacter pylori and cultured human epithelial cell lines was developed using an enzyme-linked, biotin-streptavidin bacterial-adhesion assay. The present study suggests that this method is suitable for evaluating the participation of lectin interactions in the adhesion of H. pylori to cultured HeLa S3 and Kato III cells, both fixed and glycosidase-treated cells, as well as assessing glycoconjugated binding inhibition studies. The time-course and dose-dependent kinetics of the biotin-labeled H. pylori adhesion th the formaldehyde-fixed Hela S3 and Kato III cell lines exhibited saturation. In addition, the binding of the biotin-labeled H. pylori to the formaldehyde-fixed cultured cells was partially blocked by pre-incubation with glycoconjugates and polyclonal antibodies against a heparan sulfate binding protein from H. pylori.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.1
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• pp.42-48
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• 2015

The mannitol transporter Enzyme $II^{Mtl}$ of the bacterial phosphotransferase system has two cytoplasmic phosphoryl transfer domains $IIA^{Mtl}$ and $IIB^{Mtl}$. The two domains are linked by a flexible peptide linker in mesophilic bacterial strains, whereas they are expressed as separated domains in thermophilic strains. Here, we carried out backbone assignment of $IIA^{Mtl}$ from thermophilic Thermoanaerobacter Tencongensis using a suite of heteronuclear triple resonance NMR spectroscopy. We have completed 94% of the backbone assignment, and obtained secondary structural information based on torsion angles derived from the chemical shifts. $IIA^{Mtl}$ of Thermoanaerobacter Tencongensis is predicted to have six ${\beta}$ strands and six ${\alpha}$ helices, which is analogous to $IIA^{Mtl}$ of Escherichia coli.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.140-147
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• 1999

A gene expressing organophosphorus acid (OPA) anhydrolases have been cloned from Alteromonas haloplanktis strain and expressed in bacterial strain BL21. Crude extract was prepared from the transformed bacterial strain BL2l and used in testing its degrading capability of real nerve gas, soman and sarin. Within 1 minute after the start of the reaction, nearly 65% of the soman added to the reactant(3mM) was degraded by adding 1 mg of the crude extract enzyme(20.0 Unit $mg^-{1}$ crude protein). In 6 minutes, the reaction reached at its steady state, which indicates that soman was completely degraded by that time. In the case of sarin, the degradation efficiency was observed to be about 0.7 times of that of soman. If the specific activity of OPAA is enhanced by both increased expression efficiency and purification, OPAA seems to be applied for the development of decontaminant of skin, especially of eye.

• Computers and Concrete
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• v.19 no.4
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• pp.413-417
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• 2017

Concrete is a material popularly used in construction. Due to the load-bearing and external environmental factors during utilization or manufacturing, its surface is prone to flaws, such as crack and leak. To repair these superficial defects and ultimately and avoid the deterioration of the concrete's durability, numerous concrete surface protective coatings and crack repair products have been developed. Currently, studies are endeavoring to exploit the mineralization property of microbial strains for repairing concrete cracks be the repairing material for crack rehabilitation. This research aims to use bacteria, specifically B. pasteurii, in crack rehabilitation to enhance the flexural and compression strength of the repaired concrete. Serial tests at various bacterial concentrations and the same $Urea-CaCl_2$ medium concentration of 70% for crack rehabilitation were executed. The results prove that the higher the concentration of the bacterial broth, the greater the amount of calcium carbonate precipitate was induced, while using B. pasteurii broth was for crack rehabilitation. The flexural and compression strengths of the repaired concrete test samples were the greatest at 100% bacterial concentration. Compared to the control group (bacterial concentration of 0%), the flexural strength had increased by 32.58% for 1-mm crack samples and 51.01% for 2-mm crack samples, and the compression strength had increased by 28.58% and 23.85%, respectively. From the SEM and XRD test results, a greater quantity of rectangular and polygonal crystals was also found in samples with high bacterial concentrations. These tests all confirm that using bacteria in crack rehabilitation can increase the flexural and compression strength of the repaired concrete.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.574-579
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• 2010

In this study the enzyme inhibition method using dehydrogenase which has been popularly used to estimate ecotoxicity was optimized. When three bacterial strains, Escherichia coli HB101, Enterobacter asburiae KCAD-4, and Aeromonas media KCAD-13, were compared, KCAD-4 was considered as the adequate strain to estimate toxicity because of its sensitivity and reproducibility. The optimal bacterial density was estimated as $5.4{\times}10^9CFU/mL$, at which the maximum sensitivity was observed. The phosphate buffer was suitable for the reaction solution. When the reaction times required for inhibition of enzyme activity by contact of toxicants and for reaction of damaged bacteria and substrate were tested, the optimal value was estimated as 20 min and 2 hrs, respectively. It is expected that the optimized conditions can be used to develop the standardized kits to estimate ecotoxicity of heavy metals in effluent from the industrial wastewater treatment facilities.