• Journal of Microbiology
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• v.35 no.2
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• pp.127-133
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• 1997

Biosynthesis of polyhydroxybutyrate and copolymer consisting of 3-hydroxybutyrate and 3-hydroxyvalerate [poly(3HB-co-3HV)] by Bacillus thuringiensis R-510 grown with glucose or with mixtures of glucose and propionate was investigated. n-Alkanoic acids other than propionate were not precursors of 3HV units. The fraction of 3HV unit in the copolymer increased from 0 to 84 mol% of 3HV. Polymer yield decreased as the fraction of propionate was increased but the molecular weight distribution was not affected by the composition of carbon substrate. The minimum melting temperature (around 65.deg.C) of poly (3HB-co-3HV) copolymers was observed for the polymer bearing approximately 35 mol% of 3HV. Polyhydroxyalkanoates production by this organism was not dependent on nutritional limitation, but remarkably influenced by dissolved oxygen concentration in the culture medium. Low level of dissolved oxygen concentration prevented spore formation in the cells and stimulated the synthesis of polyhydroxyalkanoate. The composition of poly (3HB-co-3HV) produced by B. thuringiensis R-510 lyhydroxyalkanoate. The composition of poly(3HB-co-3HV) propduced by B. thuringiensis R-510 varied according to the growth time. However, there was no evidence that polymers isolated from cells were mixtures of immiscible polymers.

• Analytical Science and Technology
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• v.10 no.1
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• pp.75-81
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• 1997

Poly-${\beta}$-hydroxybutyrates(PHB) are well known intracellular biopolymer which are completely degraded to carbon dioxide and water in the landfill. The pressurized fermentation method was used to increase the cell growth of Alcaligenes eutrophus and productivity of PHB. The experimental data were analyzed in terms of carbon source and gas composition effects at various elevated pressures and temperatures. The results reveal that the flow rate of hydrogen gas of 0.0075vvm for the culture is better PHB production than the no hydrogen flow when fructose was used as a sole carbon source. The higher yields and productivities of PHB biosynthesized by A. eutrophus were obtained when the oxygen composition was changed from 2% to 8% at 6atm and $30^{\circ}C$.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.6
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• pp.437-443
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• 2020

Biological phosphorus removal is accomplished by exposing PAO(phosphorus accumulating organisms) to anaerobic-aerobic conversion conditions. In the anaerobic condition, PAO synthesize PHB(polyhydroxybutyrate) and simultaneously hydrolysis of poly-p resulting phosphorus(Pi) release. In aerobic condition, PAO uptake phosphorus(Pi) more than they have released. In this study, cyanobacteria Synechococcus sp., which is known to be able to synthesize PHB like PAO, was exposed to anaerobic-aerobic conversion. If Synechococcus sp. can remove excess phosphorus by the same mechanism as PAO, synergistic effects can occur through photosynthesis. Moreover, Synechococcus sp. is known to be capable of synthesizing PHB using inorganic carbon as well as organic carbon, so even if the available capacity of organic carbon decreases, it was expected to show stable phosphorus removal efficiency. In 6 hours of anaerobic condition, phosphorus release occurred in both inorganic and organic carbon conditions but SPRR(specific phosphorus release rate) of both conditions was 10 mg-P/g-MLSS/day, which was significantly lower than that of PAO. When converting to aerobic conditions, SPUR(specific phosphorus uptake rate) was about 9 mg-P/g-MLSS/day in both conditions, showing a higher uptake rate than the control condition showing SPUR of 6.4 mg-P/g-MLSS/day. But there was no difference in terms of the total amount of removal. According to this study, at least, it seems to be inappropriate to apply Synechococcus sp. to luxury uptake process for phosphorus removal.

• Journal of Biosystems Engineering
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• v.29 no.5 s.106
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• pp.457-466
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• 2004

Novel porous composite ceramic bone scaffolds composed of biodegradable PHBV(polyhydroxybutyrate-co-hydroxyvalerate) and TA(toothapatite) have been fabricated for bone tissue engineering by a modified solvent casting and particulate leach-ing method with salt-contained heat compression technique. The results of this study suggest that the PHBV-TA composite scaffold, especially the scaffold containing 30 weight$\%$ of TA may be a good candidate far bone tissue engineering of non-load bearing area in oral and maxillofacial region.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.216-216
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• 2006

A special group of polymers, those from renewable resources, has attracted an increasing amount of attention over the last two decades, due to two major reasons: environmental concerns and the limitations of our finite petroleum resources. Generally, polymers from renewable resources (PFRR) can be classified into three groups: (1) natural polymers, such as starch, protein and cellulose; (2) synthetic polymers from natural monomers, such as polylactic acid (PLA); and (3) polymers from microbial fermentation, such as polyhydroxybutyrate (PHB). Like many other petroleum based polymers, various properties of PFRR are also vastly improved through blending and composites formation.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.352-352
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• 2006

Corynebacterium glutamicum, which is well known as an amino acid fermentation bacterium, has been used as a producer of poly(3-hydroxybutyrate) [P(3HB)]. P(3HB) was synthesized in recombinant C. glutamicum harboring the expression plasmid vector with a strong promoter for cell surface protein gene derived from C. glutamicum and P(3HB) biosynthetic gene operon derived from Ralstonia eutropha. The expression of P(3HB) synthase gene was detected by enzyme activity assay. Intracellular P(3HB) was microscopically observed as inclusion granules and its content was calculated to be 22.5 % (w/w) with molecular weight of $2.1{\times}10^{5}$ and polydispersity of 1.63.

• Advances in materials Research
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• v.4 no.4
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• pp.207-214
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• 2015

It has been reported in the technical literature that orotic acid can be used in order to induce improved crystallization of biodegradable and biocompatible polymers like poly(L-lactic acid), polyhydroxybutyrate and poly(hydroxybutyrate-co-hydroxyhexaonat). The expected advantage of the changed crystalline structure is a reinforcing effect of the polymers. A lot of papers reported about the application of inorganic and organic agents for acceleration of heterogeneous nucleation. This study reports on an attempt to use orotic acid as appropriate non-toxic nucleating agent for improving mechanical properties of isotactic polypropylene. Special attention is given to demonstrate the effect of nucleation in a typical melt spinning process in order to improve the mechanical properties. The effects were demonstrated using rheology, thermal analysis and tensile testing.

• Korean Journal of Microbiology
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• v.38 no.2
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• pp.144-151
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• 2002

For elucidating the relationship between the biosynthetic pathways for polyhydroxyslkanoates (PHAs) and 5-aminolevulinic acid (ALA), culture conditions for the production of these two biomaterials by Rhodopseudomonas sp. KCTC 1437 were investigated. Of the carbon substrates tested, acetic acid was the best carbon source for cell growth and PHA biosynthesis. When succinic acid was added as a co-substrate into culture medium, cell growth and PHA production were greatly increased up to 2.5 g/ι and 73% of dry cell weight, respectively. The PHA obtained from the carbon substrates tested was homopolyester of 3-hydroxybutyrate, while valeric acid was only effective for the production of copolyester consisting of 3-hydroxybutyrate and 3-hydroxyvalerate. Anaerobic light culture condition was better for PHA production and cell growth than anaerobic dark or aerobic dark culture condition. The organism was capable of synthesizing ALA when glycine and succinic acid were added to the culture medium. ALA was produced to ca.400 mg/ι when levulinic acid, soccinic acid, and glycine were repeatedly added with a reductant (sodim thioglycolate). However, the presence of glycine, levulinic acid and sodium glycolate inhibited the cell growth and the conversion of carbon substrates to PHA. From these results it is apparent that the production yields of PHA and ALA could not be increased simultaneously because the optimal conditions for the production of PHA and ALA are opposed to each other.

• Korean Journal of Soil Science and Fertilizer
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• v.36 no.5
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• pp.290-303
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• 2003

Modern agriculture has been heavily dependent on chemical fertilizers to meet the food demands of ever increasing population. Progressive depletion of major plant nutrients in soil due to intensive cultivation practices has also necessitated the use of higher dose of chemical fertilizers particularly in soils where the organic matter content is very low. Indiscriminate use of chemical fertilizers and pressure on agriculturists to enhance per area crop yields has led to fast depletion of fossil fuel resources with concomitant increase in the prices of chemical fertilizers and also led to environmental pollution. Hence, the current trend throughout the world is to explore the possibility of using alternate nutrient sources or increasing the efficiency of chemical fertilizers by supplementing them with organic fertilizers and bioinoculants comprising largely microbes like, bacteria, fungi, algae etc to enhance nitrogen and phosphates in the soil thus creating a sustainable agricultural environment. Among the different microbial inoculants or biofertilizers, Azospirillum could be a potential candidate due to its non specific host root colonization. It had the capability to fix $N_2$ in wide pH regimes and even in presence of combined nitrogen. Azospirillum inoculation can increase the crop yield to 10-25% and substitute 25% of recommended doses of nitrogenous fertilizers. Apart from nitrogen fixation, Azospirillum is also involved in the root improvement, the activity which was attributed to an increase in the rate of water and mineral uptake by roots. The ability of Azospirillum to produce phytohormones was reported to enhance the root respiration rate, metabolism and root proliferation. They have also been reported to produce polyhydroxybutyrate, that can be used as a biodegradable thermosplastic. A lot of studies have addressed improvements in enhancing its efficiency to fix nitrogen fixation and hormone production.

• Journal of Microbiology
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• v.42 no.4
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• pp.346-352
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• 2004

Poly(3-Hydroxybutyrate-co­3-Hydroxyvalerate), poly(3HB-co-3HV), copolyesters with a variety of 3HV contents (ranging from 17 to $60\;mol\%$) were produced by Alcaligenes sp. MT-16 grown on a medium containing glucose and levulinic acid in various ratios, and the effects of hydrophilicity and crystallinity on the degradability of the copolyesters were evaluated. Measurements of thermo-mechanical pro­perties and Fourier-transform infrared spectroscopy in the attenuated total reflectance revealed that the hydrophilicity and crystallinity of poly(3HB-co-3HV) copolyesters decreased as 3HV content in the copolyester increased. When the prepared copolyester film samples were non-enzymatically hydrolysed in 0.01 N NaOH solution, the weights of all samples were found to have undergone no changes over a period of 20 weeks. In contrast, the copolyester film samples were degraded by the action of extra­cellular polyhydroxybutyrate depolymerase from Emericellopsis minima W2. The overall rate of weight loss was higher in the films containing higher amounts of 3HV, suggesting that the enzymatic degra­dation of the copolyester is more dependent on the crystallinity of the copolyester than on its hydro­philicity. Our results suggest that the degradability characteristics of poly(3HB-co-3HV) copolyesters, as well as their thermo-mechanical properties, are greatly influenced by the 3HV content in the copoly­esters.