• 멤브레인
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• 제33권6호
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• pp.390-397
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• 2023

석유기반 플라스틱의 대체제인 폴리하드록시부틸레이트(polyhydroxybutyrate, PHB)의 기존 추출방법은 분자량 감소 및 물성 변형을 일으킨다. 본 연구에서는 기능화 된 탄소나노튜브(carbon nanotube, CNT)를 부착한 돌기형 탄소나노튜브 분리막의 여과를 통해 물리적 파쇄를 발생시켜 미생물 내 축적된 PHB를 추출하고자 하였다. 돌기형 탄소나노튜브 분리막의 물리적 파쇄를 확인하기 위해 대장균 용액으로 여과 실험을 수행하여 불활성화를 관찰하였다. 또한 PHB를 축적한 미생물 용액의 여과를 수행하여 PHB가 추출되었는지 확인하였더니 가장 대표적인 추출방법인 chloroform과 비교하여도 여과로 인한 추출이 4% 높은 성능을 가진 것을 관찰하였다. 본 결과를 통해 친환경적 바이오 플라스틱 회수를 위한 돌기형 탄소나노튜브 분리막의 적용 가능성을 확인하였다.

• KSBB Journal
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• 제13권1호
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• pp.96-100
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• 1998

두 개의 프로모터 (trc와 Pp)를 Alcaligenes eutrophus에서 유래된 PHA 오페론에 삽입하여 재조합 대장균에서 분자량이 큰 polyhydroxybutyrate (PHB)를 얻고자 하였다. 두 개의 프로모터는 hydroxybutyric CoA와 PHA 중합반응의 유전자 발현을 각각 독립적으로 제어하기 위해 설계된 것이다 새로운 합성오페론을 포함한 플라즈미드는 E. coli DH5 $\alpha$ 에 transformation 되어 PHB 생산에 이용되었다. 본 실험의 가설로서 PHA 합성오페론의 IPTG에 의한 유도가 없을 경우 낮은 pHA synthase의 활성이 고분자 중합반응의 개시제 농도를 줄여주어 결과적으로 높은 연결수의 고분자를 생성할 것이라는 모델을 세웠다. 실제로 IPTG의 공급이 없는 발효실험을 통해 평균분자량이 $2.5{\times}10^7$ 인 거대 고분자를 얻을 수 있었다. PHA 생합성에 관여는 효소의 활성 분석으로 3-hydroxybutyric CoA의 중합을 촉매하는 효소인 PHA synthase의 활성을 가지고 In vivo에서 분자량이 제어됨을 확인하였다.

• 한국환경과학회지
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• 제33권2호
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• pp.121-129
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• 2024

The study investigated the effect of thermo-alkaline pretreatment on the solubilization of polyhydroxybutyrate (PHB) and its potential to enhance of thermophilic anaerobic digestion, focusing on biochemical methane potential (BMP) and methane production rate, using two different particle sizes of PHB (1500 ㎛ and 400 ㎛). Thermo-alkaline pretreatment tests were conducted at 90 ℃ for 24 hours with varying NaOH dosages from 0-80% (w/w). BMP tests with untreated PHB exhibited methane production ranging from 150.4~225.4 mL CH₄/g COD and 21.5~24.2 mL CH₄/g VSS/d, indicating higher methane production for smaller particle sizes of PHB, 400 ㎛. Thermo-alkaline pretreatment tests achieved a 95.3% PHB solubilization efficiency when 400 ㎛ PHB particles were treated with 80% NaOH dosage at 90 ℃ for 24 hours. BMP tests with pretreated PHB showed substantial improvement in thermophilic anaerobic digestion, with an increase of up to 112% in BMP and up to 168% in methane production rate. The results suggest that a combined pretreatment process, including physical (400 ㎛ PHB particles) and thermo-alkaline (90 ℃, 40-80% NaOH dosage, and 24 hours reaction time), is required for high-rate thermophilic anaerobic digestion of PHB with enhanced methane production.

• Journal of Microbiology and Biotechnology
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• 제29권5호
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• pp.776-784
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• 2019

Polyhydroxybutyrate (PHB), the most well-known polyhydroxyalkanoate, is a bio-based, biodegradable polymer that has the potential to replace petroleum-based plastics. Lignocellulose hydrolysate, a non-edible resource, is a promising substrate for the sustainable, fermentative production of PHB. However, its application is limited by the generation of inhibitors during the pretreatment processes. In this study, we investigated the feasibility of PHB production in E. coli in the presence of inhibitors found in lignocellulose hydrolysates. Our results show that the introduction of PHB synthetic genes (bktB, phaB, and phaC from Ralstonia eutropha H16) improved cell growth in the presence of the inhibitors such as furfural, 4-hydroxybenzaldehyde, and vanillin, suggesting that PHB synthetic genes confer resistance to these inhibitors. In addition, increased PHB production was observed in the presence of furfural as opposed to the absence of furfural, suggesting that this compound could be used to stimulate PHB production. Our findings indicate that PHB production using lignocellulose hydrolysates in recombinant E. coli could be an innovative strategy for cost-effective PHB production, and PHB could be a good target product from lignocellulose hydrolysates, especially glucose.

• Journal of Plant Biotechnology
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• 제49권3호
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• pp.257-270
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• 2022

The aim of this work was to prepare a new biodegradable polyhydroxybutyrate (PHB) submicron fiber mat loaded with hypericin-rich Hypericum perforatum raw extract by centrifugal spinning technology, an alternative approach to the traditional method of electrospinning to fabricate nanofibers or microfibers from solutions at high speed and low cost. Hypericins in methanol/acetone extract of H. perforatum were determined by UHPLC-MS/MS and HPLC/PDA. Submicron fiber mats composed of pure PHB or PHB enriched with H. perforatum extract were prepared using a pilot plant demonstrator for the centrifugal spinning technology and characterized by SEM. Singlet oxygen production was quantified by the 1,3-diphenylisobenzofuran (DPIBF) method in hexane. The results proved a significant production of singlet oxygen by the prepared submicron fiber mat. We also found a significant antibacterial activity against the bacterial strain Escherichia coli CCM 5417 by a method in accordance with JIS Z 2801/ISO 22196 standards. The H. perforatum extract-enriched PHB submicron fiber mats showed potential for the development of self-cleaning and antimicrobial air filters.

• 한국환경과학회지
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• 제31권7호
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• pp.609-616
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• 2022

In this study, the effect of different reaction times for thermal-alkaline pretreatment on the solubilization and biogasification of polyhydroxybutyrate (PHB) were evaluated. Thermal-alkaline pretreatment tests were performed at 73 ℃ and pH 13 at 0-120 h reaction times. The mesophilic anaerobic batch tests were performed with untreated and pretreated PHB samples. The increase in the pretreatment reaction time results in a 52.8-98.8% increase of the abiotic solubilization efficiency of the PHB samples. The reaction time required to achieve solubilization efficiencies of 50%, 90%, and 95% were 10.5, 52.0, and 89.6 h, respectively. The biogasification of the untreated PHB samples achieved a specific methane production rate of 3.6 mL CH₄/g VSS/d and require 101.3 d for complete biogasification. The thermal-alkaline pretreatment significantly improved specific methane production rate (10.2-16.0 time increase), lag time (shortened by 76-81%), and time for complete biogasification (shortened by 21-83%) for the biogasification of the PHB samples when compared to those of the untreated PHB samples. The improvement was higher as the reaction time of the thermal-alkaline pretreatment increased. The findings of this study could be used as a valuable reference for the optimization of the biogasification process in the treatment of PHB wastes.

• Journal of Microbiology and Biotechnology
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• 제34권3호
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• pp.700-709
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• 2024

Polyhydroxybutyrate (PHB) production from lignocellulosic biomass is economically beneficial. Because lignocellulosic biomass is a mixture rich in glucose and xylose, Escherichia coli, which prefers glucose, needs to overcome glucose repression for efficient biosugar use. To avoid glucose repression, here, we overexpressed a xylose regulator (xylR) in an E. coli strain expressing bktB, phaB, and phaC from Cupriavidus necator and evaluated the effect of xylR on PHB production. XylR overexpression increased xylose consumption from 0% to 46.53% and produced 4.45-fold more PHB than the control strain without xylR in a 1% sugar mixture of glucose and xylose (1:1). When the xylR-overexpressed strain was applied to sugars from lignocellulosic biomass, cell growth and PHB production of the strain showed a 4.7-fold increase from the control strain, yielding 2.58 ± 0.02 g/l PHB and 4.43 ± 0.28 g/l dry cell weight in a 1% hydrolysate mixture. XylR overexpression increased the expression of xylose operon genes by up to 1.7-fold. Moreover, the effect of xylR was substantially different in various E. coli strains. Overall, the results showed the effect of xylR overexpression on PHB production in a non-native PHB producer and the possible application of xylR for xylose utilization in E. coli.

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 1998년도 제38회 춘계학술발표대회
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• pp.47.1-47.1
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• 1998

• 분석과학
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• 제10권1호
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• pp.75-81
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• 1997

Poly-${\beta}$-hydroxybutyrates(PEB)는 토양에서 완전히 이산화탄소와 물로 분해되는 세포 내에 생성되는 고분자 물질로 잘 알려져 있다. Alcaligenes eutrophus의 세포 성장과 PHB의 생산성을 증가시키기 위해서 가압배양법이 사용되었다. 실험 데이타를 다양한 가압과 온도하에서 탄소 공급원과 기체성분의 영향에 관해서 분석한 결과 0.0075vvm의 기체수소를 공급한 배양이 수소를 공급하지 않은 배양에 비해 더 나은 PEB 생산성을 나타내었고, 6atm, $30^{\circ}C$에서 산소의 성분비를 2%에서 8%로 변화시켰을 때 더 높은 수율과 PEB의 생산성을 얻을 수 있었다.

• 상하수도학회지
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• 제34권6호
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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.