• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.3
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• pp.196-200
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• 2004

The supra molecular weight poly(〔R〕-3-hydroxybutyrate) (PH B), having a molecular weight greater than 2 million Da, has recently been found to possess improved mechanical properties compared with the normal molecular weight PHB, which has a molecular weight of less than 1 million Da. However, applications for this PHB have been hampered due to the difficulty of its production. Reported here, is the development of a new metabolically engineered Escherichia coli strain and its fermentation for high level production of supra molecular weight PHB. Recombinant E. coli strains, harboring plasm ids of different copy numbers containing the Alcaligenes latus PHB biosynthesis genes, were cultured and the molecular weights of the accumulated PHB were compared. When the recombinant E. coli XL1-Blue, harboring a medium-copy-number pJC2 containing the A. latus PHB biosynthesis genes, was cultivated by fed-batch culture at pH 6.0, supra molecular weight PHB could be produced at up to 89.8 g/L with a productivity of 2.07 g PHB/L-h. The molecular weight of PHB obtained under these conditions was as high as 22 MDa, exceeding by an order of magnitude the molecular weight of PHB typically produced in Ralstonia eutropha or recombinant E. coli.

• Journal of Microbiology
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• v.38 no.2
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• pp.99-104
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• 2000

Hydrogen peroxide has been used in cleaning the piping of an advanced high-purity water system that supplies ultra-high purity water (UHPW) for 16 megabyte DRAM semiconductor manufacturing. The level of hydrogen peroxide-resistant bacteria in UHPW water was monitored prior to and after disinfecting the piping with hydrogen peroxide. Most of the bacteria isolated after hydrogen peroxide disinfection were highly resistant to hydrogen peroxide. However, the percentage of resistant bacteria decreased with time. The hydrogen peroxide-resistant bacteria were identified as Micrococcus luteus, Bacillus cereus, Alcaligenes latus, Xanthomonas sp. and Flavobacterium indologenes. The susceptibility of the bacteria to hydrogen peroxide was tested as either planktonic cells or attached cells on glass. Attached bacteria as the biofilm on glass exhibited increased hydrogen peroxide resistnace, with the resistance increasing with respect to the age of the biofilm regrowth on piping after hydrogen peroxide treatment. In order to optimize the cleaning strategy for piping of the high-purity water system, the disinfecting effect of hydrogen preoxide and peracetic acid on the bacteria was evaluated. The combined use of hydrogen peroxide and peracetic acid was very effective in killing attached bacteria as well as planktonic bacteria.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.73-76
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• 2000

A novel, continuous bioreactor system combining a bubble column (absorption section) and a two-phase bioreactor (degradation section) has been designed to treat a gas stream containing benzene. The bubble column contained hexadecane as an absorbent for benzene, and was systemically chosen considering physical, biological, environmental, operational and economic factors. This solvent has infinite solubility for benzene and very low volatility. After absorbing benzene in the bubble column, the hexadecane served as the organic phase of the two-phase partitioning bioreactor, transferring benzene into the aqueous phase where it was degraded by Alcaligenes xylosoxidans Y234. The hexadecane was then continuously recirculated back to the absorber section for the removal of additional benzene. All mass transfer and biodegradation characteristics in this system were investigated prior to operation of the integrated unit, and these included: the mass transfer rate of benzene in the absorption column, the mass transfer rate of benzene from the organic phase into the aqueous phase in the two-phase bioreactor, the stripping rate of benzene out of the two-phase bioreactor, etc. All of these parameters were incorporated into model equations, which were used to investigate the effects of operating conditions on the performance of the system. Several experiments were conducted to show the feasibility of this system. This process is believed to be very practical for the treatment of high concentrations of gaseous pollutants.

• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.872-876
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• 2001

Topological changes caused by the alkaline and enzymatic attacks of solution-grown, chain-folded lamellar crystals (SGCs) of poly[(R)-3-hydroxybutyrate] P(3HB) have been studied in order to investigate the chain-folding structure in P(3HB) crystal regions. NaOH and an extracellular PHB depolymerase purified from Alcaligenes faecalis T1 were used for alkaline and enzymatic hydrolysis, respectively. The measurements were performed on crystals attached to a substrate which is inactive to degradation mediums. Both alkaline and enzymatic attacks lead to a breakup of the lamellar crystals along the crystallographic b-axis during initial erosion. Since hydrolysis preferentially occurs in amorphous regions, this morphological result reflects relatively loosely packed chains in core parts of lamellar crystals. Additionally, it was supported by the ridge formation along the b-axis in the lamellar crystals after thermal treatment at a low temperature because of the thermally sensitive nature of the loosely packed chains in lamellar crystals. However, the alkaline hydrolysis accompanied the chain erosions or scissions in quasi-regular folded lamellar surfaces due to smaller size of alkaline ions in comparison to the enzyme, resulting in the decrease of molecular weight.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.668-676
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• 2001

Pseudomonas sp. strain SY5 is a PCB-degrading bacterium [24] that includes two different enzymes (BphC1 and BphC2) encoding 2,3-dihdroxybiphenyl 1,2-dioxygenase and BphD encoding 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase. The bphC1 and bphC2 genes were found to consist of 897 based encoding 299 amino acids and 882 bases encoding 294 amino acids, respectively, whereas the bphD gene consisted of 861 bases encoding 287 amino acids. According to a homology search, a 50% and 39% similarity between the bphC1 and bphC2 genes at the nucleotide and amino acid level was shown, respectively. The bphC1 gene showed a 38% and 45% similarity at the amino acid level to Alcaligenes eutrophus A5 and Rhodococcus rhodochrous, respectively, whereas, bphC2 showed a 95% and 43% similarity, respectively. A comparison of the deduced amino acid sequence of the bphD product of Pseudomonas sp. SY5 with that of A. eutrophus A5, Pseudomons sp. KKS102, and LB400 showed a sequence identity of 92, 92, and 79%, respectively. Strain SY5 was originally isolated from municipal sewage containing recalcitrant organic compounds an found to have a high degradability of various aromatic compounds [23]. The current study found that strain SY5 had two extradiol-type dioxygenases, which did not hybridize with each other as they had a low similarity, yet a similar structure of evolutionarily conserved amino acids residues for catalytic activity between BphC1 and BphC2 was observed.

• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.590-598
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• 2011

Bacterial assimilation of $CO_2$ into stable biomolecules using electrochemical reducing power may be an effective method to reduce atmospheric $CO_2$ without fossil fuel combustion. For the enrichment of the $CO_2$-fixing bacteria using electrochemical reducing power as an energy source, a cylinder-type electrochemical bioreactor with a built-in anode compartment was developed. A graphite felt cathode modified with neutral red (NR-graphite cathode) was used as a solid electron mediator to induce bacterial cells to fix $CO_2$ using electrochemical reducing power. Bacterial $CO_2$ consumption was calculated based on the variation in the ratio of $CO_2$ to $N_2$ in the gas reservoir. $CO_2$ consumed by the bacteria grown in the electrochemical bioreactor (2,000 ml) reached a maximum of approximately 1,500 ml per week. Time-coursed variations in the bacterial community grown with the electrochemical reducing power and $CO_2$ in the mineral-based medium were analyzed via temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region. Some of the bacterial community constituents noted at the initial time disappeared completely, but some of them observed as DNA signs at the initial time were clearly enriched in the electrochemical bioreactor during 24 weeks of incubation. Finally, Alcaligenes sp. and Achromobacter sp., which are capable of autotrophically fixing $CO_2$, were enriched to major constituents of the bacterial community in the electrochemical bioreactor.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.125-128
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• 2000

A recycling reactor system operated under sequential anoxic and oxic conditions for the swine wastewater has been developed, in which piggery slurry is fermentatively and aerobically treated and then part of the effluent recycled to the pigsty. This system significantly removes offensive smells (at both pigsty and treatment plant), BOD and other loads, and appears to be costeffective for the small-scale farms. The most dominant heterotrophs were Alcaligenes faecalis, Brevundimonas diminuta and Streptococcus sp. in order while lactic acid bacteria were dominantly observed in the anoxic tank. We propose a novel monitoring system for a recycling piggery slurry treatment system through neural networks. Here we tried to model treatment process for each tank(influent, fermentation, aeration, first sedimentation and fourth sedimentation tanks) in the system based on population densities of heterotrophic and lactic acid bacteria. Principle component analysis(PCA) was first applied to identify a relation between input(microbial densities and parameters for the treatment such as population densities of heterotrophic and lactic acid bacteria, suspended solids (SS), COD, $NH_3-N$, ortho-P, and total-P) and output, and then multilayer neural networks were employed to model the treatment process for each tank. PCA filtration of input data as microbial densities was found to facilitate the modeling procedure for the system monitoring even with a relatively lower number of input. Neural networks independently trained for each treatment tank and their subsequent combinatorial data analysis allowed a successful prediction of the treatment system for at least two days.

• Journal of Microbiology and Biotechnology
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• v.7 no.4
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• pp.229-236
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• 1997

A gene, $phbC_{2.4.1}$ encoding poly-3-hydroxybutyric acid (PHB) synthase of Rhodobacter sphaeroides 2.4.1 was cloned by employing heterologous expression in Escherichia coli. R. sphaeroides chromosomal DNA partially digested with MboI was cloned in pUC19 followed by mobilization into E. coli harbouring $phbA,B_{AC}$ in pRK415, which code for ${\beta}$-ketothiolase and acetoacetyl CoA reductase of Alcaligenes eutrophus, respectively. Two E. coli clones carrying R. sphaeroides chromosomal fragment of $phbC_{2.4.1}$ in pUC19 were selected from ca. 10,000 colonies. The PHB-producing colonies had an opaque white appearance due to the intracellular accumulation of PHB. The structure of PHB produced by the recombinant E. coli as well as from R. sphaeroides 2.4.1 was confirmed by [$H^{+}$]-nuclear magnetic resonance (NMR) spectroscopy. Restriction analysis of the two pUC19 clones revealed that one insert DNA fragment is contained as a part of the other cloned fragment. An open reading frame of 601 amino acids of $phbC_{2.4.1}$ with approximate M.W. of 66 kDa was found from nucleotide sequence determination of the 2.8-kb SaiI-PstI restriction endonuclease fragment which had been narrowed down to support PHB synthesis through heterologous expression in the E. coli harbouring $phbA,B_{AC}$. The promoter (s) of the $phbC_{2.4.1}$ were localized within a 340-bp DNA region upstream of the $phbC_{2.4.1}$ start codon according to heterologous expression analysis.

• Korean Journal of Clinical Laboratory Science
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• v.39 no.3
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• pp.167-177
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• 2007

From the total 121,294 clinical materials submitted to the Department of Laboratory Medicine of "C" hospital from December 1, 2004 to November 30, 2006, 3,408 Pseudomonas spp. were isolated. The isolation frequencies of Pseudomonas spp. were as follows, P. aeruginosa 95.5%, P. putida 2.5%, P. fluorescens 0.8%, along with low frequencies of P. luteola, P. alcaligenes, P. stutzeri, P. oryzihabitants, P. mendocina and unidentified Pseudomonas species. The isolation rates of Pseudomonas spp. according to season and sex were evenly distributed. The isolated frequency of Pseudomonas spp. in male was two times higher than that of in female showing significantly more male patients in surgical areas and more female patients in internal areas (p<0.001). In monthly analysis, Pseudomonas spp. were the most frequently isolated in July (10.4%), but lowest in February (5.6%). Half of Pseudomonas spp. were isolated from sputum (48.2%). In the susceptibility analysis of Pseudomonas spp. by VITEK II AST cards, the Pseudomonas spp showing higher susceptibility against antimicrobial agents were piperacillin/tazobactam (82.7%) in P. aeruginosa; amikacin (84.7%), colistin (83.3%) in P. putida; and amikacin (96.3%), cefepime (87.5%), ceftazidime (87.5%) ciprofloxacin (92.3%), colistin (88.5%) gentamicin (96.2%), isepamicin (96,1%), meropenem (92.3%), netilmicin (96.0%), piperacillin/ tazobactam (95.4%) and tobramycin (92.6%) in P. fluorescens.

• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.4
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• pp.49-56
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• 2003

The strain Ralstonia eutopha JMP134 (formerly Alcaligenes eutrophus JMP134) can degrade trichloroethylene(TCE) through a chromosomal phenol-dependent pathway. The phenol hydroxylase was previously found to be a single responsible enzyme for TEC degradation. Here, we demonstrate that a recombinant bacterium, R. eutopha AEK301, one of Tn5-induced mutants of JMP134 containing a recombinant plasmid pYK3011, degrades TCE in the absence of inducer, phenol and in the presence of various carbon sources. Complete removal of TCE ($50{\mu}M$) was observed in minimal medium containing only 0.05% ethanol as a carbon source within 24 hours. The bacterium removed $200{\mu}M$ of TCE to below detectable level within two days under non-selective pressure. When TCE concentration was increased up to $400{\mu}M$, the degradation had been continued until two days, then ceased with removal of 70% of detectable TCE.