• 미생물학회지
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• 제36권2호
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• pp.84-90
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• 2000

Psudomonas sp. RY-1이 생성하는 extracellular depolymerase system을 이용하여 단위체의 결가지에 서로 다른 탄소 길이와 불포와기를 함유하는 medium-chain-length polyhdroxyalkanoates (MCL-PHAs)의 생분해도를 시럼실 조건에서 조사하였다. 생분애도는 평파내지에서의 clear zone 형성, 효소 처리에 의한 고분자 현탁액의 탁도 감소 및 호흡량의 경시적 변화로 측정하였다. Pseudomonas sp. RY-1은 MCL-PHA depolymerase의 생성을 통하여 조사된 모든 종류의 MCl-PHAs를 분해할 수 있었으나, 이 효소의 생성은 쉽게 이용될수 있는 이차기질에 의해 저해받는 것으로 나타났다. MCl-PHAs의 분해율이 단위체의 탄소수가 홀수개로 구성된 고분자에 비하여 보다 높았다. 곁가지에 분포화기를 함유한 MCl-PHAs는 불포화기를 갖지 아니하는 고분자에 비하여 분해가 빠르게 이루어졌으며, 이들의 분해는 고분자의 결정화도와 밀접한 관련이 있는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제22권3호
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• pp.371-377
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• 2012

The present study describes medium-chain-length polyhydroxyalkanoates (mcl-PHAs) production by the Pseudomonas Gl01 strain isolated from mixed microbial communities utilized for PHAs synthesis. A two-step fed-batch fermentation was conducted with glucose and waste rapeseed oil as the main carbon source for obtaining cell growth and mcl-PHAs accumulation, respectively. The results show that the Pseudomonas Gl01 strain is capable of growing and accumulating mcl-PHAs using a waste oily carbon source. The biomass value reached 3.0 g/l of CDW with 20% of PHAs content within 48 h of cultivation. The polymer was purified from lyophilized cells and analyzed by gas chromatography (GC). The results revealed that the monomeric composition of the obtained polyesters depended on the available substrate. When glucose was used in the growth phase, 3-hydroxyundecanoate and 3-hydroxydodecanoate were found in the polymer composition, whereas in the PHAs-accumulating stage, the Pseudomonas Gl01 strain synthesized mcl-PHAs consisting mainly of 3-hydroxyoctanoate and 3-hydroxydecanoate. The transcriptional analysis using reverse-transcription real-time PCR reaction revealed that the phaC1 gene could be transcribed simultaneously to the phaZ gene.

• KSBB Journal
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• 제10권4호
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• pp.406-420
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• 1995

Polyhydroxyalkanoates[PHAs] are the polyester of hydroxyalkanoates(HAs) synthesized by numerous bacteria as an intracellular carbon and energy storage compound and accumulated as granules in the cytoplasm of the cells under unbalanced growth condition in the presence of excess carbon source. Even though PHAs have been recognized as good candidates for biodegradable plastics, their high price compared with conventional plastics has limited their use in a wide mange of applications. To reduce the high production cost of PHAs, many group of scientists have devoted much efforts to improve productivity by employing various microorganisms and by developing efficient culture techniques. The strategies of producing PHAs to a high concentration with high productivity and their potential applications are reviewed.

• Journal of Microbiology
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• 제45권2호
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• pp.87-97
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• 2007

Medium-chain-length polyhydroxyalkanoates (MCL-PHAs), which have constituents with a typical chain length of $C_{6}-C_{14}$, are polyesters that are synthesized and accumulated in a wide variety of Gram-negative bacteria, mainly pseudomonads. These biopolyesters are promising materials for various applications because they have useful mechanical properties and are biodegradable and biocompatible. The versatile metabolic capacity of some Pseudomonas spp. enables them to synthesize MCL-PHAs that contain various functional substituents; these MCL-PHAs are of great interest because these functional groups can improve the physical properties of the polymers, allowing the creation of tailor-made products. Moreover, some functional substituents can be modified by chemical reactions to obtain more useful groups that can extend the potential applications of MCL-PHAs as environmentally friendly polymers and functional biomaterials for use in biomedical fields. Although MCL-PHAs are water-insoluble, hydrophobic polymers, they can be degraded by microorganisms that produce extracellular MCL-PHA depolymerase. MCL-PHA-degraders are relatively uncommon in natural environments and, to date, only a limited number of MCL-PHA depolymerases have been investigated at the molecular level. All known MCL-PHA depolymerases share a highly significant similarity in amino acid sequences, as well as several enzymatic characteristics. This paper reviews recent advances in our knowledge of MCL-PHAs, with particular emphasis on the findings by our research group.

• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.206-215
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• 2005

Polyhydroxyalkanoates (PHAs) are homo or hetero polyesters of (R)-hydroxyalkanoates accumulated in various microorganisms under growth-limiting condition in the presence of excess carbon source. They have been suggested as biodegradable substitutes for chemically synthesized polymers. Recombinant Escherichia coli is one of the promising host strains for the economical production of PHAs, and has been extensively investigated for the process development. The heterologous PHA biosynthetic pathways have been established through the metabolic engineering and inherent metabolic pathways of E. coli have been redirected to supply PHA precursors. Fermentation strategies for cultivating these recombinant E. coli strains have also been developed for the efficient production of PHAs. Nowadays, short-chain-length (SCL) PHAs are being re-invited due to its improved mechanical properties and possible applications in the biomedical area. In this article, recent advances in the development of metabolically engineered E. coli strains for the enhanced production of SCL-PHAs are reviewed. Also, medical applications of SCL-PHAs are discussed.

• 대한환경공학회지
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• 제37권6호
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• pp.363-370
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• 2015

인공폐수로 연속회분식 하수처리시스템에서 바이오플라스틱인 PHAs의 생산에 대하여 연구하였다. 실험은 하수처리장에서 식종슬러지를 채취하고, 실험실 내에서 제작된 인공하수를 이용하여 4 L 규모의 2조의 연속회분식반응기로 수행하였다. 인공하수의 영양조건(C/N/P)은 42:10:1로 운전되었으며, 연속회분식반응기는 호기상태에서 Feast/Famine 조건을 부여하는 ADF (aerobic dynamic feeding)의 SBR 1과 혐기/호기조건에서 Feast/Famine 조건을 부여하는 AODF (anaerobic/oxic dynamic feeding)의 SBR 2로 운전하였다. PHAs의 생산은 AODF가 ADF 보다 우수하였으며, ADOF 에서 바이오매스 대비 최대 40.0%(w/w)로 높게 생산되었으며, 구조적 및 열적 물성도 우수한 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제20권3호
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• pp.594-601
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• 2010

Azotobacter chroococcum H23 (CECT 4435), Azotobacter vinelandii UWD, and Azotobacter vinelandii (ATCC 12837), members of the family Pseudomonadaceae, were used to evaluate their capacity to grow and accumulate polyhydroxyalkanoates (PHAs) using two-phase olive mill wastewater (TPOMW, alpeorujo) diluted at different concentrations as the sole carbon source. The PHAs amounts (g/l) increased clearly when the TPOMW samples were previously digested under anaerobic conditions. The MNR analysis demonstrated that the bacterial strains formed only homopolymers containing $\beta$-hydroxybutyrate, either when grown in diluted TPOMW medium or diluted anaerobically digested TPOMW medium. COD values of the diluted anaerobically digested waste were measured before and after the aerobic PHA-storing phase, and a clear reduction (72%) was recorded after 72 h of incubation. The results obtained in this study suggest the perspectives for using these bacterial strains to produce PHAs from TPOMW, and in parallel, contribute efficiently to the bioremediation of this waste. This fact seems essential if bioplastics are to become competitive products.

• Journal of Microbiology and Biotechnology
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• 제32권1호
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• pp.110-116
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• 2022

Polyhydroxyalkanoates (PHAs) are emerging as alternatives to plastics by replacing fossil fuels with renewable raw substrates. Herein, we present the construction of engineered Escherichia coli strains to produce short-chain-length PHAs (scl-PHAs), including the monomers 4-hydroxyvalerate (4HV) and 3-hydroxyvalerate (3HV) produced from levulinic acid (LA). First, an E. coli strain expressing genes (lvaEDABC) from the LA metabolic pathway of Pseudomonas putida KT2440 was constructed to generate 4HV-CoA and 3HV-CoA. Second, both PhaAB enzymes from Cupriavidus necator H16 were expressed to supply 3-hydroxybutyrate (3HB)-CoA from acetyl-CoA. Finally, PHA synthase (PhaC_Cv) from Chromobacterium violaceum was introduced for the subsequent polymerization of these three monomers. The resulting E. coli strains produced four PHAs (w/w% of dry cell weight): 9.1 wt% P(4HV), 1.7 wt% P(3HV-co-4HV), 24.2 wt% P(3HB-co-4HV), and 35.6 wt% P(3HB-co-3HV-co-4HV).

• Journal of Microbiology and Biotechnology
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• 제13권4호
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• pp.632-635
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• 2003

Novel poly(3-hydroxyalkanoates), PHAs, having either methoxy or ethoxy groups as the terminal hydrophilic moieties, were biosynthesized by Pseudolnons oleovorans. grown either solely with 11-alkoxyundecanoic acid or 8-alkoxyoctanoic acid, or grown with a mixture of 6-alkoxyhexanoic acid and nonanoic acid. The PHA synthesized from 11-methoxyundecanoic acid consisted of 88 mol% 3-hydroxy-7-methoxyheptanoate and 12 mol% 3-hydroxy-9-methoxynonanoate. However, the PHA produced from 11-ethoxyundecanoic acid consisted of 56 mol% 3-hydroxy-5-ethoxypentanoate and 44 mol% 3-hydroxy-7-ethoxyheptanoate. The high solubility of the PHAs in methanol and ethanol indicated that the alkoxy groups in the side chains resulted in the formation of PHAs with an enhanced hydrophilicity.

• Elastomers and Composites
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• 제50권3호
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• pp.175-183
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• 2015

A series of fluorinated aromatic poly(hydroxyamide)s (PHAs) were synthesized by direct polycondensation of diacides containing 2,6-dimethylphenoxy group and quinoxaline ring in the main chain with 2,2-bis-(3-amino-4-hydroxyphenyl) hexafluoropropane. The PHAs had relatively low inherent viscosities in the range of 0.35~0.43 dL/g at $35^{\circ}C$ in DMAc solution. All PHAs exhibited excellent solubility in aprotic solvents such as NMP, DMAc, DMF and DMSO as well as in common organic solvents such as pyridine, THF, and m-cresol at room temperature. However, the poly(benzoxazole)s (PBOs) were quite insoluble in all organic solvents except partially soluble in concentrated sulfuric acid. The PBOs showed glass transition temperatures between 233 and $284^{\circ}C$ by DSC and maximum weight loss temperatures in the range of $536-546^{\circ}C$ by TGA.