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

• 대한환경공학회지
• /
• 제37권6호
• /
• pp.363-370
• /
• 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
• /
• 제15권1호
• /
• pp.206-215
• /
• 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.

• Journal of Microbiology and Biotechnology
• /
• 제20권3호
• /
• pp.594-601
• /
• 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
• /
• 제32권1호
• /
• pp.110-116
• /
• 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
• /
• 제22권3호
• /
• pp.371-377
• /
• 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.

• Journal of Microbiology and Biotechnology
• /
• 제20권5호
• /
• pp.853-861
• /
• 2010

High substrate costs decrease the profitability of polyhydroxyalkanoates (PHAs) production, and thus low-cost carbon substrates coming from agricultural and industrial residuals are tested for the production of these biopolymers. Among them, crude glycerol, formed as a by-product during biodiesel production, seems to be the most promising source of carbon. The object of this study was to characterize the mixed population responsible for the conversion of crude glycerol into PHAs by cultivation-dependent and -independent methods. Enrichment of the microbial community was monitored by applying the Ribosomal Intergenic Spacer Analysis (RISA), and the identification of community members was based on 16S rRNA gene sequencing of cultivable species. Molecular analysis revealed that mixed populations consisted of microorganisms affiliated with four bacterial lineages: ${\alpha}$, ${\gamma}$-Proteobacteria, Actinobacteria, and Bacteroides. Among these, three Pseudomonas strains and Rhodobacter sp. possessed genes coding for polyhydroxyalkanoates synthase. Comparative analysis revealed that most of the microorganisms detected by direct molecular analysis were obtained by the traditional culturing method.

• Journal of Microbiology and Biotechnology
• /
• 제27권5호
• /
• pp.990-994
• /
• 2017

Polyhydroxyalkanoates (PHAs) are biodegradable plastics produced by bacteria, but their use in diverse applications is prohibited by high production costs. To reduce these costs, the conversion by Pseudomonas strains of PHAs from crude sludge palm oil (SPO) as an inexpensive renewable raw material was tested. Pseudomonas putida S12 was found to produce the highest yield (~41%) of elastomeric medium-chain-length (MCL)-PHAs from SPO. The MCL-PHA characteristics were analyzed by gas-chromatography/mass spectrometry, gel permeation chromatography, and differential scanning calorimetry. These findings may contribute to more widespread use of PHAs by reducing PHA production costs.

• 생명과학회지
• /
• 제33권8호
• /
• pp.680-691
• /
• 2023

오일 피크, 기후변화 그리고 미세 플라스틱과 관련된 석유합성 플라스틱의 생산과 사용은, 지속 가능한 인류 생활을 위협하는 범세계적 이슈로 대두되고 있다. 이러한 문제를 해결하기 위해 다양한 생분해성 친환경 바이오플라스틱 소재가 대안이 되고 있으며, 그중 주목받고 있는 소재 중 하나는 polyhydroxyalkanoates (PHA) 생분해성 바이오플라스틱이다. 본 총설은 PHA 생산공정에 이용될 수 있는 해양 미생물의 산업적 활용 이점과 현재까지 밝혀진 해양미생물의 생산성을 비교하고, 이들이 산업에서 활용되기 위해 필요한 연구개발 현황에 대해 조사하였다. 조사 결과 해양미생물로부터 생산된 PHA는 석유합성 플라스틱이 보유한 다양한 물리적 특성을 띄는 중합체 소재로의 대체 가능성과, 배지 제조 시 해수를 사용할 수 있는 장점, 특별한 멸균 과정이 필요치 않은 장점, 그리고 분리 정제 과정 등에서 비용 절감의 장점을 제공할 수 있음을 확인하였다. 하지만 해양미생물의 PHA 생산성은 육상에서 분리된 상용화 균주에 비해 다소 떨어지는 효율을 보이는 것을 확인하였다. 이러한 문제점을 해결하기 위해 최근 선진 omics 기반 합성 미생물학 기반 기술을 활용하여, 고밀도 연속배양기술 개발, PHA 효율 증진 및 다양한 시장 요구에 필요한 생분해성 플라스틱 소재 개발이 미래 플라스틱 대체 소재 개발에 필요한 연구임을 확인하였다.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2000년도 춘계학술발표대회
• /
• pp.579-582
• /
• 2000

Enantiomerically pure hydroxycarboxylic acids have great potential as chiral building blocks in fine chemicals due to their easily modificable two functional groups. Microbial polyhydroxyalkanoates (PHAs) can have more than one hundred of hydroxycarboxylic acids as monomeric constituents by growing cells under various conditions. All of the monomeric constituents are enantiomerically pure in (R)-conformation if there is a chiral center. Therefore, efficient production of enantiomerically pure hydroxycarboxylic acids by degrading PHAs is possible. In this presentation, we report on the development of a novel method for the preparation of (R)-hydroxybutyric acid by in vivo depolymerization of Polyhydroxybutyrae.