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

• 수산해양교육연구
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• 제25권4호
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• pp.766-774
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• 2013

Biodegradable polybutylene succinate(PBS) is a kind of environmentally friendly plastics for fisheries, because it can mitigate the ghost fishing problem caused by gill-net and trap fisheries. To evaluate durability of PBS monofilament, each of different diameter 3 types of monofilaments were spun and exposed to 56 month outdoor and then their gravity, modification of surface, breaking strength, and elongation were analysed. The gravity of PBS monofilament was estimated to be approximately 1.24 when spinning ratio from 4.8 to 6.1. PBS monofilaments did not show any crack after 56 month exposed to outdoor and load-elastic elongation curve was showed sigmoid type. Decreasing ratio of elongation was appeared in the thinnest monofilament 0.2mm diameter and breaking strength was in the thickest monofilament 0.4mm diameter. Breaking strength and elongation at break were decreased rapidly after 48 month exposed to outdoor. Breaking strength reduced linearly after 48 month exposure, while no such linear relationship was found in the case of elongation at break. In results, it was investigated that the durability of PBS monofilament nets for gillnet and trap were 24, 50 month when keep to land, respectively.

• 한국환경보건학회지
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• 제28권2호
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• pp.99-108
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• 2002

This study was carried out to evaluate the Physicochemical characteristics of mined waste(separated waste and soil) and to predict environmental effect of an old landfill site located at north of Seoul. Municipal solid waster(MSW) had been disposed of at the old landfill site used in this study for about 2 years(1990-1992). The old landfill site selected for this study had accepted mainly municipal solid waste. The landfill-mined waste contained separated waste (40.9%) and soil(59.1%) by wet weight basis. The separated waste consisted of combustible(91.0%) and non-combustible(9.0%). The combustible waste was mainly non-biodegradable plastics. The low heating value of the separated combustible waste, which is calculated by Dulong's equation, was as high as 3,470kcal/kg. According to the Korean Extraction Procedure, separated waste and soil were proved to be not hazardous. The total content of heavy metal in the separated waste and soil met standard of California State, USA. Therefore the separated waste may be relandfilled at a sanitary landfill site and/or burned up at an incinerator, and the separated old soil may be used ad landfill cover-soil at a sanitary landfill site. Water quality of two streams was grade IV, of which water could be used as industrial and agricultural water. The streams near the landfill site might not be contaminated by leachate from the old landfill site. It was estimated that organic matter in the old landfill site would not be actively biodegraded within a short period of time.

• KSBB Journal
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• 제30권4호
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• pp.161-165
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• 2015

Lactic acid and its derivatives are widely used in the food, pharmaceutical, and cosmetic industries. It is also a major raw material for the production of poly-lactic acid (PLA), a biodegradable and environmentally friendly polymer and a possible alternative to synthetic plastics derived from petroleum. For PLA production by new strains of lactic acid bacteria (LAB), we screened LAB isolates from shellfish. A total of 51 LAB were isolated from 7 types of shellfishes. Lactic acid production of individual isolates was examined using high-performance liquid chromatography using a Chiralpak MA column and an ultraviolet detector. Lactobacillus plantarum T-3 was selected as the most stress-resistant strain, with minimal inhibition concentrations of 1.2 M NaCl, 15% ethanol, and 0.0020% hydrogen peroxide. In a 1 L fermentation experiment, $\small{D}$-lactic acid production of 19.91 g/L fermentation broth was achieved after 9 h cultivation, whereas the maximum production of total lactic acid was 41.37 g/L at 24 h.

• Advances in materials Research
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• 제6권4호
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• pp.329-341
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• 2017

The challenge of replacing conventional plastics with biodegradable composite materials has attracted much attention in product design, particularly in the tensile-related areas of application. In this study, fibres extracted from oil palm empty fruit bunch (EFB) were treated and utilized in reinforcing polyester matrix by hand lay-up technique. The effect of fibre loading and combined influence of alkali and silane treatments on porosity and water absorption parameters, and its correlation with the tensile behaviour of composites was analyzed. The results showed that tensile strength decreased whilst modulus of elasticity, water absorption and porosity parameters increased with increasing fibre loading. The composites of treated oil palm EFB fibre exhibited improved values of 2.47 MPa to 3.78 MPa for tensile strength; 1.75 MPa to 2.04 MPa for modulus of elasticity; 3.43% to 1.68% for porosity and 3.51% to 3.12% for water absorption at respective 10 wt.% fibre loadings. A correlation between porosity and water absorption with tensile behavior of composites of oil palm EFB fibre and positive effect of fibre treatment was established, which clearly demonstrate a connection between processing and physical properties with tensile behavior of fibre composites. Accordingly, a further exploitation of economic significance of oil palm EFB fibres composites in areas of low-to-medium tensile strength application is inferred.

• 한국포장학회지
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• 제29권2호
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• pp.103-110
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• 2023

The study aimed to enhance the properties of polylactic acid (PLA), a biodegradable and biocompatible substitute for fossil-based plastics. Since the applicability of PLA has been limited because of its toughness and brittleness, microfibrillated cellulose (MFC) and propolis were introduced into PLA. As a result, the PLA film with MFC/propolis showed significant improvements in mechanical strength, elongation, and storage modulus, while also experiencing a decrease in the glass transition temperature. Additionally, the presence of polyphenols in propolis led to a reduction in light transmittance in the UV wavelength range. These enhancements are attributed to MFC tightly bonding with PLA polymers, and propolis acting as a plasticizer and mediator between MFC and PLA, preventing agglomeration. These reinforced PLA films have the potential to be used in flexible packaging for light-sensitive products.

• 청정기술
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• 제19권4호
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• pp.401-409
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• 2013

폐플라스틱에 의한 환경오염 증가로 생분해성 고분자에 대한 관심이 커지고 있다. 본 연구에서는 생분해성 고분자인 폴리 L-락타이드(polylactic acid, PLA)와 폴리 L-락타이드(polylactic acid, PLA)/폴리 부틸렌 숙신산(polybutylene succinate, PBS)(90/10)수지를 기지재료로 하고 유기 크로사이트(cloisite ) 20을 나노 클레이(clay) 20으로 사용하여 이축압출기에서 Clay-20 함량별 로 압출시켜 나노복합체를 제조하였다. 사출성형기로 사출성형시편을 제조하여 나노복합체의 열적, 기계적, 형태학적 및 라만 분광학 특성을 시차열량분석기(differential scanning calorimeter, DSC), 인장시험기, 주사전자현미경(scanning electron microcopy, SEM), 라만-현미경 분광광도계로 조사하였고, 또한 가수분해특성을 조사하였다. 시차열량분석기와 주사전자현미경 시험 결과에서 PLA/Clay-20과 PLA/PBS/Clay-20 나노복합체의 결정화도가 Clay-20 함량이 증가함에 따라 증가하였고, Clay-20과 PLA 및 PLA/PBS 수지가 서로 상용성이 있는 것으로 확인되었다. 또한 Clay-20 함량이 증가함에 따라 두 나노복합체의 인장강도는 감소하지만 신도, 충격강도, 인장탄성률 및 굴곡탄성률이 증가하였다. 특히 Clay-20이 5 wt% 첨가된 PLA/Clay-20과 PLA/PBS/Clay-20 나노복합체의 충격강도는 순수 PLA와 PLA/PBS (90/10) 보다 2배 이상으로 증가하였다. Clay-20 3 wt% 첨가된 PLA/Clay-20 나노복합체의 가수분해속도는 순수 PLA 가수분해속도보다 두 배 정도 빨랐다. 이는 유기화 처리된 Clay-20 나노입자 표면의 친수성으로 계면에서 가수분해가 쉽게 일어나기 때문인 것으로 판단된다. 본 연구에서 적당량의 Clay-20 첨가로 PLA의 기계적특성 개선과 생분해 특성 조절 가능성을 확인하였다.

• 생명과학회지
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• 제33권8호
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• pp.680-691
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• 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.

• 한국산학기술학회논문지
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• 제13권11호
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• pp.5595-5600
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• 2012

본 논문은 poly(lactic acid)의 내열성을 향상시키기 위한 결정화 핵제의 검토 및 연구에 대한 것이다. 네 종류의 미세분말 핵제인 금속염 2,2'-methylene bis(4,6-di-tert-butylphenol) salt를 결정화 핵제로 사용하였다. 폴리머 컴파운드의 열적 및 기계적 특성은 DSC, HDT, UTM을 통해 측정하였다. 이 연구의 결과로서, 컴파운드 한 폴리머 샘플들의 내열특성은 핵제의 함량 증가와 미세분말 일수록 선형적으로 증가 하였다. 그 중에서MPZ2의 함량이 2 wt%일때 가장 높은 내열특성을 나타내었으며, PL98Z2 컴파운드의 열변형 온도는 $116^{\circ}C$를 나타내었다 (ASTM D 648, 0.455MPa).

• Journal of Microbiology and Biotechnology
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• 제22권8호
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• pp.1141-1147
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• 2012

Polyhydroxyalkanoate (PHA) is a class of biodegradable plastics that have great potential applications in the near future. In this study, the micro-biodiversity and productivity of PHA-accumulating bacteria in activated sludge from a domestic wastewater treatment plant were investigated. A previously reported primer set and a self-designed primer set (phaCF1BO/phaCR2BO) were both used to amplify the PHA synthase (phaC) gene of isolated colonies. The new primers demonstrated higher sensitivity for phaC, and combining the PCR results of the two primer sets was able to widen the range of detected genera and raise the sensitivity to nearly 90%. Results showed that 85.3% of the identified bacteria were Gram-negative, with Ralstonia as the dominant genus, and 14.7% were Gram-positive. In addition, Zoogloea and Rhizobium contained the highest amounts of intracellular PHA. It is apparent that glucose was a better carbon source than pentone or tryptone for promoting PHA production in Micrococcus. Two different classes, class I and class II, of phaC were detected from alphaproteobacteria, betaproteobacteria, and gammaproteobacteria, indicating the wide diversity of PHA-accumulating bacteria in this particular sampling site. Simultaneous wastewater treatment and PHA production is promising by adopting the high PHA-accumulating bacteria isolated from activated sludge.