• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.175-178
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• 2000

Biodegradability of the $poly({\beta}-hydroxybutyrate-co-3 -hydroxyvalerate)$ [PHB/V] containing 0, 10 and 15mol% hydroxyvalerate [HV] was studied. Bioderadability of PHB/V was evaluated at $30^{\circ}C$ for 58 days and $55^{\circ}C$ for 33 days by monitoring the time-dependent changes in weight loss(erosion) of aerobic conditions in a temperature-controlled microcosms containing the earthworm cast($30^{\circ}C$) and compost ($55^{\circ}C$). It was found that PHB/V biodegradability occurred with increasing HV monomer concentration from 0 mol% to 15 mol%.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.6
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• pp.540-545
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• 2005

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3HB-co-3HV), copolyesters, with 3-hydroxyvalerate (3HV) contents ranging from 17 to 60 mol%, were produced by Alcaligenes sp. MT-16, and their biocompatibility evaluated by the growth of Chinese hamster ovary (CHO) cells and the adsorption of blood proteins and platelets onto their film surfaces. The number of CHO cells that adhered to and grew on these films was higher with increasing 3HV content. In contrast, the tendency for blood proteins and platelets to adhere to the copolyester surfaces significantly decreased with increasing 3HV content. Examination of the surface morphology using atomic force microscopy revealed that the surface roughness was an important factor in determining the biocompatibility of theses copolyesters. The results obtained in this study suggest that poly(3HB-co-3HV) copolyesters, with >30 mol% 3HV, may be useful in biocompatible biomedical applications.

• Microbiology and Biotechnology Letters
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• v.19 no.1
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• pp.94-99
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• 1991

- The further study for the identification of the previously reported pink-pigmented facultative methylotrophic bacterium (PPFM) GL-10 was carried out. The PPFM GL-10 was Gram nagative, rod, and motile by a single polarly inserted flagellum. The colonies were smooth, pink, circular, along with convex with entire margin. The isolate could utilize C1 compounds and a variety of multicarbon substrates as sole carbon and energy source. The isolate was obligately aerobic, and exhibited both catalase and oxidase activities. The deoxyribonucleic acid base composition was 65-67 mol% guanine plus cytosine. The isolate was mostly identical with Methylobacterium extorquens and named Methylobacterium sp. strain GL-10. Methylobacterium GL-10 accumulated a copolyester of 3-hydroxybutyrate and 3-hydroxyvalerate (poly-3HB/3 HV) when grown in nitrogen-free culture media containing sodium propionate as substrate at the second polyester accumulation stage. The composition of copolyester, as determined from $^1h$ NMR spectra, was 23 mol% of 3-hydroxyvalerate (3HV).

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.588-592
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• 1995

Fed-batch fermentation was used to produce the high concentrations of poly-$\beta $-hydroxybutyrate (PHB) and poly-$\beta $-(hydroxybutyrate-co-hydroxyvalerate) (PHB/V). Specific growth rate ($\mu $), yield of cell from glucose (Y$_{x/s}$) were calculated from the two samples in 3 to 5 hours of interval and they were reflected on the determination of glucose feeding rate to maintain the glucose concentration at around 10 g/l in the culture broth. PHB was accumulated after the nitrogen became limited at 60 g/l of dry cell weight by changing ammonia water to 4N-NaOH solution. As results, the final dry cell weight (DCW) of 170 g/l, PHB of 115 g/l were obtained in 50 hours and the overall productivity was 2.4 g/l$\cdot $h. After PHB accumulation, cosubstrate of glucose and propionic acid (PA) was fed to accumulate PHB/V. But, PA feeding rate was decreased from 3 g/l$\cdot $h to 1 g/l$\cdot $h to prevent PA from accumulating to high level in the broth, which is very inhibitory to the cells. As results, DCW, PHB and PHV were 147.5 g/l, 90 g/l and 8 mole % of hydroxyvalerate, respectively.

• Journal of Adhesion and Interface
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• v.16 no.3
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• pp.108-115
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• 2015

In the present work, we investigated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene nanocomposites. The electrical, hydrophobic properties and thermal properties of the nanocomposite films having different graphene contents were investigated. The scanning electron microscopy (SEM) morphology showed good dispersion of graphene layers in the PHBV matrix. Based on the X-ray diffraction and differential scanning calorimetry, the addition of graphene increased the crystallinity of PHBV. Thermal stability, hydrophobicity, and electrical conductivity of the nanocomposites were increased with increasing the graphene contents.

• Macromolecular Research
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• v.8 no.6
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• pp.253-260
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• 2000

Biodegradable wafers were prepared with poly (hydroxybutyrate-co-hydroxyvalerate) (PHBV;5, 10, and 15 mole% for 3-hydroxyvalerate) by simple heat pressing method for the sustained release of antibiotic agent, gentamicin sulfate (GS) to investigate the possibility of the treatment for osteomyelitis. The effects of hydroxyvalerate (HV) content, thickness of wafers, various types of additives such as sodium dodecyl sulfate (SDS), microcrystalline cellulose, polyvinylpyrrolidone, and hydroxypropylcellulose (HPC), and different initial drug loading ratio on the release profile have been investigated. In vitro release studies showed that different release patterns and rates could be achieved by simply modifying factors in the preparation conditions. PHBV wafers with 3 mm thickness, 10% of GS initial loading, 15% of HV content and addition of 5% of SDS and HPC were free from initial burst and a near-zero-order sustained release was observed for over 30 days. It might be suggested that the mechanisms of G5 release may be more predominant simple dissolution and diffusion of GS than erosion of PHBV in our system.

• KSBB Journal
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• v.13 no.5
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• pp.615-620
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• 1998

The readily fermentable carbon sources in swine were acetic acid, propionic acid and butyric acid at the average concentrations of 7.2 g/L, 2.2 g/L and 2.7 g/L, respectively. The swine waste also contained excess nitrogen and other mineral sources. In shake flask experiments, the optimal range of cell growth for Azotobacter vinelandii UWD were 1.0∼3.5 g/L of acetic acid, 0.7∼2.0 g/L of propionic acid and 0.5∼2.0 g/L of butyric acid. A mixture of these three acids simulating two times diluted swine waste supported the best cell growth but the amount of carbon sources was limited. In shake flask and fermentor experiments, an addition of 30 g/L of glucose increased the final cell dry weight 8 times while the final poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) concentration increased 86 times compared with using acid mixture only. A. vinelandii UWD preferred organic acids in the sequence of acetic acid, propionic acid, butyric acid, and valeric acid.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.1-10
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• 2017

In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene oxide (GO) nanocomposite films containing various content of GO were prepared using solution casting method. The effect of GO content on Young's modulus and dispersion of GO in PHBV matrix was investigated. Also, the thermomechanical properties, oxygen transmission rates and hydrolytic degradation of PHBV/GO nanocomposite films were studied. The addition of GO into PHBV improves the Young's modulus and decreases thermal expansion coefficient. The improvement can be mainly attributed to good dispersion of GO and interfacial interactions between PHBV and GO. Furthermore, PHBV/GO nanocomposite films show good oxygen barrier properties. PHBV/GO nanocomposites show lower hydrolytic degradation rates with increasing content of GO.

• Korean Journal of Microbiology
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• v.48 no.3
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• pp.200-206
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• 2012

A bacterial strain capable of synthesizing polyhydroxyalkanoates (PHAs) with an unusual pattern of monomer units was isolated from activated sludge using the enrichment culture technique. The organism, identified as Pseudomonas aeruginosa P-5, produced polyesters consisting of 3-hydroxyvalerate and medium-chain-length (MCL) 3-hydroxyalkanoate monomer units when $C_{-odd}$ alkanoic acids such as nonanoic acid and heptanoic acid were fed as the sole carbon source. Solvent fractionation experiments using chloroform and hexane revealed that the 3-hydroxyalkanoate monomer units in these polyesters were copolymerized. The molar concentration of 3-hydroxyvalerate in the polyesters produced were significantly elevated up to 26 mol% by adding 1.0 g/L valeric acid as the cosubstrate. These copolyesters were sticky with low degrees of crystallinity. The PHA synthase genes were cloned, and the deduced amino acid sequences were determined. P. aeruginosa P-5 possessed genes encoding MCL-PHA synthases (PhaC1 and PhaC2) but lacked the short-chain-length PHA synthase gene, suggesting that the MCL-PHA synthases from P. aeruginosa P-5 are uniquely active for polymerizing (R)-3-hydroxyvaleryl-CoA as well as MCL (R)-3-hydroxyacyl-CoAs.

• Microbiology and Biotechnology Letters
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• v.24 no.1
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• pp.92-100
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• 1996

For the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(P(3HB-co-3HV)) from butyric acid and valeric acid, 10 strains of bacteria capable of producing P(3HB-co-3HV) were isolated from soil. Among them, the strain HJ-067 showed the best ability of producing P(3HB-co-3HV), and was indentified as a Azotobacter sp. For the production of P(3HB-co-3HV), the optimum concentrations of butyric and valeric acid were 3.0g/l, respectively. The most effective nitrogen source was $(NH_4)_{2}SO_4$ at an optimum concentration of 0.75g/l, which was equivalent to 21.36 in C/N ratio. Deficiency of the cationic metal ions ($Zn^{2+},\;Co^{2+},\;Mn^{2+}$) in the proguction medium had stimulating effect on P(3HB-co-3HV) accumulation, especially in the manganese. deficient medium. The optimum temperature for P(3HB-co-3HV) production was 27$^{\circ}C$ and the optimum initial pH was 7.0. Under the optimum conditions, 1.82g/l of P(3HB-co-3HV) and 3.00g/l of dry biomass were produced after 36 hour cultivation, and the P(3HB-co-3HV) yield and HV% were 60.60% (w/w), 15.92%, respectively.