• Journal of Microbiology and Biotechnology
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• 제30권2호
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• pp.244-247
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• 2020

We have expressed extracellular poly(3-hydroxybutyrate) (PHB) depolymerase of Ralstonia pickettii T1 on the Escherichia coli surface using Pseudomonas OprF protein as a fusion partner by C-terminal deletion-fusion strategy. Surface display of depolymerase was confirmed by flow cytometry, immunofluorescence microscopy and whole cell hydrolase activity. For the application, depolymerase was used as an immobilized catalyst of enantioselective hydrolysis reaction for the first time. After 48 h, (R)-methyl mandelate was completely hydrolyzed, and (S)-mandelic acid was produced with over 99% enantiomeric excess. Our findings suggest that surface displayed depolymerase on E. coli can be used as an enantioselective biocatalyst.

• Journal of Microbiology and Biotechnology
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• 제11권2호
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• pp.310-316
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• 2001

Poly-3-hydroxybutyrate (PHB) synthase catalyzed the last enzymic step to synthesize the intracellular PHB of Rhodobacter sphaeroides. No PHB was detected when the phbC coding for PhB synthase was interrupted, and its expression was regulated at the level of transcription. The cellular PHB content increased about four- to six-fold during the growth transition from the exponential to the early stationary phase under both aerobic and photoheterotrophic conditions. The PHB content during the aerobic growth seemed to be determined by the PhB synthase activity. However, the PHB synthase activity of photoheterotrophically grown cells did not correlate with the PhB content, suggesting a photoheterotrophic regulation different from the aerobic control. Thus, the PHB content of R. sphaeroides was regulated at the transcription level only under aerobic conditions.

• Journal of Microbiology and Biotechnology
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• 제13권3호
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• pp.477-481
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• 2003

The community escape response of Rhodobacter sphaeroides is exerted through the action of CerR and CerI, which code for a LuxR-type regulatory protein and acylhomoserine lactone synthase, respectively. Deletion of chromosomal DNA including cerR and cerI (mutant RI) or insertional interruption of cert (mutant AP3) resulted in two-fold increase in the cellular poly-${\beta}$-hydroxybutyrate (PHB) content In comparison with the wild-type under aerobic growth conditions. The PHB synthase (PhbC) activities of the cer mutants were doubled, and the enzyme expression was regulated at the level of phbC transcription. Thus, CerR, possibly in response to autoinducer (AI), appears to modulate the PHB content of aerobically grown cells by downregulating phbC transcription.

• Journal of Microbiology and Biotechnology
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• 제9권5호
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• pp.554-561
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• 1999

A novel estimation method was investigated for determining the concentrations of residual biomass, poly-3-hydroxybutyrate (PHB), and main nutrients including carbon and nitrogen sources, phosphate, and mineral ions from the supplied amount of ammonia solution used for a pH-control solution and nitrogen source in a PHB fermentation. The estimation equations for a batch culture and a fed-batch culture were derived from the relationship between the growth rate of residual biomass and the feed rate of the pH-control solution, and then were applied to the batch culture and the fed-batch cultures of Alcaligenes latus. This method was successfully applied to estimate the concentrations of residual biomass, PHB, and nutrients.

• Journal of Microbiology and Biotechnology
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• 제9권6호
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• pp.751-756
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• 1999

For mass production of poly(3-hydroxybutyrate) (PHB), high cell density cultures of Ralstonia eutropha were carried out in 2.5-1 and 60-1 fermentors by two fed-batch culture techniques of nitrogen and phosphate limitation. When the nitrogen limitation technique was employed using both an on-line glucose monitoring and control system, a high concentration level of PHB (121g/l) was obtained in the small-scale fermentor of 2.5 1. However, the PHB concentration obtained in a large-scale fermentor of 60 1 only turned out to be 60g/l. In contrast, when another fed-batch culture technique of the phosphate-limitation employing dissolved oxygen (DO) stat glucose feeding was used, a large amount of PHB was successfully produced in both 60-1 and 2.5-1 fermentors. In a 2.5-1 fermentor, concentrations of PHB and cells obtained in 58 h were 175 and 210 g/l, respectively, which corresponded to the PHB productivity level of 3.02 g/l/h. In a 60-1 fermentor, a final cell concentration of 221 g/l and a PHB concentration of 180 g/l with PHB productivity level of 3.75 g/l/h were obtained in 48h. PHB content and yield from glucose were 81% and 0.38g PHB/g glucose, respectively. These data suggest that the phosphate limitation technique is more effective compared to nitrogen limitation in the mass production of PHB by R. eutropha of a large scale.

• KSBB Journal
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• 제14권4호
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• pp.422-428
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• 1999

Alcaligenes latus 유래의 phbC 유전자를 A. eutrophus에 재도입시킨 형질전환균주를 이용하여 높은 4HB 몰분율을 갖는 P(3HB-4HB)의 고농도 생산을 시도하였다. 형질전환균주는 총균체량, P(3HB-4HB) 농도, 그리고 축적률에서 모균주에 비해 다소 증가한 반면 P(3HB-4HB)내의 4HB 몰분율은 23.5 mol%로 모균주의 12.3 mol%에 비해 현저히 증가하였다. 이는 phbC유전자의 증폭으로 인해 해당과정에서 생성된 3HB와 전구물질인 ${\gamma}$-butyrolacton에서 전환된 4HB의 중합반응이 촉진되기 때문으로 사료된다. 또한 ${\gamma}$-butyrolacton의 농도 $Mg^{2-}$ 이온, 그리고 citrate 첨가량이 P(3HB-4HB)의 농도, 축적률, 그리고 4HB 몰분율에 미치는 영향을 검토하였다. P(3HB-4HB)내의 4HB 몰분율을 증대시키기 위하여 일반적으로 사용되는 2단계 배양법을 변형시켜 ${\gamma}$-butyrolacton과 citrate의 첨가시기를 늦춘 2단계 배양법을 활용하여 P(3HB-4HB)내의 4HB 몰분율을 61.0 mol%로 증가시킬 수 있었다. 또한 ${\gamma}$-butyrolacton의 첨가량을 조절하여 P(3HB-4HB)내의 4HB 몰분율이 92.0 mol%에 이르는 homopolymeric P(4HB)를 생산할 수 있었으며, 그 구조를 $^1$H-NMR을 통해 확인하였다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.223-226
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• 2000

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권5호
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• pp.295-302
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• 2002

To understand the utilization property of light energy, Synechococcus sp. MA19, a poly-${\beta}$-hydroxybutyrate (PHB) producer, was cultivated at the different incident light intensities of 15.3, 50.0 and 78.2 W/$m^2$ using media with and without phosphate. From the results of metabolic flux analysis, it was found that the cell yield based on ATP synthesis was estimated as $3.5{\times}10^{-3}$ kg-biomass/mol-ATP in these cultures. Under the examined conditions, there were no significant differences in the efficiency of light energy conversion to chemical energies estimated as ATP synthesis and reducing potential (NADH + NADPH) formation whether the PHB synthesis took place or not. The energy converted from light to ATP was kept relatively high around the energy absorbed by the cells of $2.5-3.0{\times}10^{6} J\;h^{-1}\;kg^{-1}$, whereas the energy of reducing potential was hardly changed in the examined range of the energy absorbed by the cells.

• Journal of Microbiology and Biotechnology
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• 제33권8호
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• pp.1076-1083
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• 2023

Poly(3-hydroxybutyrate) (PHB) is a biodegradable and biocompatible bioplastic. Effective PHB degradation in nutrient-poor environments is required for industrial and practical applications of PHB. To screen for PHB-degrading strains, PHB double-layer plates were prepared and three new Bacillus infantis species with PHB-degrading ability were isolated from the soil. In addition, phaZ and bdhA of all isolated B. infantis were confirmed using a Bacillus sp. universal primer set and established polymerase chain reaction conditions. To evaluate the effective PHB degradation ability under nutrient-deficient conditions, PHB film degradation was performed in mineral medium, resulting in a PHB degradation rate of 98.71% for B. infantis PD3, which was confirmed in 5 d. Physical changes in the degraded PHB films were analyzed. The decrease in molecular weight due to biodegradation was confirmed using gel permeation chromatography and surface erosion of the PHB film was observed using scanning electron microscopy. To the best of our knowledge, this is the first study on B. infantis showing its excellent PHB degradation ability and is expected to contribute to PHB commercialization and industrial composting.

• 미생물학회지
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• 제36권4호
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• pp.299-305
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• 2000

생분해성 플라스틱으로 현재 상업화에 가장 근접해 있는 poly-3-hydroxybutyrate (PHB), $Sky-Green^R$(SG) 및 $Mater-Bi^R$(MB)를 활성오니토 및 경작토에 매립하여 PHB 분해세균 3주, SG 분해세균 3주 및 MB 분해세균 1주를 분리하였다. PHB 분해세균은 Flavimonas oryzihabitans, Corynebacterium pseudodiphtheriticum 및 Micrococcus diversus로, SG 분해세균은 Pseudomonas vesicuraris, Pasteurlla multocida 및 Flavobacterium odoratum으로, MB 분해세균은 Pseudomonas vesicuraris로 동정되었다. 각 플라스틱 film을 함유한 무기염 액체배지에서 28일 간의 생분해성 실험 결과 평균 중량감소는 PHB와 SG은 각각 44~69% 및 25~32%, MB는 29%를 나타내어 PHB의 생분해성이 가장 우수하였다. 각 플라스틱 film의 활성오니토 매립 전과 후의 표면 변화를 조사한 결과 미생물이 다공성의 film 표면에 많은 colony를 형성하는 것이 SEM으로 관찰되었다. PHB, SG 및 MB의 무생물적 분해와 F. oryzihabitans에 의한 미생물학적 생분해를 TOC와 pH 변화로 측정하여 비교 분석하였을 때, SG과 MB는 분해 정도가 서로 유사하였으나 PHB는 SG는 MB에 비하여 dir 3배 더 빠르게 무생물적 분해가 일어났다. Yeast extract를 포함한 배지에서 PHB, GS 및 MB의 분해는 yeast extract를 포함하지 않은 배지에서 보다 훨씬 빠르게 안정되었으며, 두 경우 모두 PHB의 분해는 SG 및 MB에 비하여 더 빠르게 일어졌다.