• Journal of Microbiology and Biotechnology
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• v.4 no.2
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• pp.146-150
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• 1994

Production of poly-$\beta$-hydroxybutyrate (PHB) in fed-batch fermentation was studied. Utilization of carbon for PHB biosynthesis was investigated by using feeding solutions with different ratios of carbon to nitrogen (C/N). It was observed that at a high C/N ratio carbon source was more preferably utilized for PHB accumulation while its consumption for cellular metabolism appeared to be more favored at a low C/N value. A high cell concentration (184 g/l) was achieved when ammonium hydroxide solution was fed to control the pH, which was also utilized as the sole nitrogen source. For the mass production of PHB, two-stage fed-batch operations were carried out where PHB accumulation was observed to be stimulated by switching the ammonium feeding mode to the nitrogen limiting condition. A large amount of PHB (108 g/l) was obtained with cellular content of 80% within 50 hrs of operation.

• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.333-336
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• 2001

An isolated phbC gene from Alcaligenes latus was reintroduced into the parent A. latus through the transformation process, and the effect of the amplified phbC gene on the biosynthesis of P(3-hydroxybutyrate-3-hydroxyvalerate) [P(3HB-3HV)] and P(3-hydroxybutyrate-4-hydroxybutyrate) [P(3HB-4HB)] in the transformant A. latus was investigated. The biosynthesis rate and content of the above copolymers increased up to 1.3-fold after enforcing its own phbC gene, and the molar fractions of 3HV and 4HB in P(3HB-3HV) and P(3HB-4HB) also changed remarkably from 35.0 to 48.0% and from 34.0 to 56.0%, respectively, showing a critical role of PHB synthase which catalyzes the polymerizing reactions between eiher 3HV or 4HB from precursor compounds and 3HB.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.588-592
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• 1995

Fed-batch fermentation was used to produce the high concentrations of poly-$\beta $-hydroxybutyrate (PHB) and poly-$\beta $-(hydroxybutyrate-co-hydroxyvalerate) (PHB/V). Specific growth rate ($\mu $), yield of cell from glucose (Y$_{x/s}$) were calculated from the two samples in 3 to 5 hours of interval and they were reflected on the determination of glucose feeding rate to maintain the glucose concentration at around 10 g/l in the culture broth. PHB was accumulated after the nitrogen became limited at 60 g/l of dry cell weight by changing ammonia water to 4N-NaOH solution. As results, the final dry cell weight (DCW) of 170 g/l, PHB of 115 g/l were obtained in 50 hours and the overall productivity was 2.4 g/l$\cdot $h. After PHB accumulation, cosubstrate of glucose and propionic acid (PA) was fed to accumulate PHB/V. But, PA feeding rate was decreased from 3 g/l$\cdot $h to 1 g/l$\cdot $h to prevent PA from accumulating to high level in the broth, which is very inhibitory to the cells. As results, DCW, PHB and PHV were 147.5 g/l, 90 g/l and 8 mole % of hydroxyvalerate, respectively.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.8
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• pp.3803-3807
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• 2012

Prohibitin (PHB), an evolutionarily-conserved protein, has been found to be over-expressed in gastric cancer and be closely related with tumor malignancy. In this study, to investigate the relationship between PHB expression and cell apoptosis in the BGC823 gastric cancer cell line, low and high expression PHB in BGC823 cells was accomplished using RNA interference technology and gene transfer techniques. Cell proliferation, cell cycling, apoptosis, Bax, Bcl-2 and Cyt.c protein expression and the activation of Caspase-3,9 were assessed after 48h. Over-expression of PHB gene in BGC823 cells resulted in slow cell growth, cell arrest in G2 phase, and an increased apoptosis ratio while the opposite was found for PHB under-expressing cells. In PHB over-expressing cells, the expression of Bax gene was increased, the expression of Bcl-2 was decreased, the activation level of Caspase-3, 9 was increased, but the activation level of Caspase-8 demonstrated no change. These results indicate that PHB induced apoptosis through the mitochondrial pathway.

• The Korean Journal of Mycology
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• v.23 no.4 s.75
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• pp.348-353
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• 1995

Biodegradability of poly (3-hydroxybutyrate) (PHB) by Penicillium pinophilum was investigated by the modified Sturm Test. The biodegradability measurement by this method was more reproducible than other conventional activated sludge methods. Optimum inoculum size for the PHB biodegradation was 1% (v/v). The degradation appeared to occur not only on the sample surface but also inside the sample because the biodegradation did not increase quite proportionally with the sample surface area. The biodegradation rate increased to an asymptotic value as the nitrogen content in the test medium increased, indicating the nitrogen source was needed for the synthesis of the PHB depolymerase.

• Journal of Life Science
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• v.18 no.12
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• pp.1625-1630
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• 2008

A microorganism capable of producing high level of poly-3-hydoxybutyrate (PHB) from xylose was isolated from soil. The isolated strain J-65 was identified as Bacillus megaterium based on the morphological, biochemical and molecular biological characteristics. The optimum temperature and pH for the growth of B. megaterium J-65 were $37^{\circ}C$ and 8.0, respectively. The optimum medium composition for the cell growth was 2% xylose, 0.25% $(NH_4)_2SO_4$, 0.3% $Na_2HPO_4{\cdot}12H_2O$, and 0.1% $KH_2PO_4$. The optimum condition for PHB accumulation was same to the optimum condition for cell growth. Copolymer of ${\beta}$-hydroxybutyric and ${\beta}$-hydroxyvaleric acid was produced when propionic acid was added to shake flasks containing 20 g/l of xylose. Fermenter culture was carried out to produce the high concentration of PHB. In batch culture, cell mass was 9.82 g/l and PHB content was 35% of dry cell weight. PHB produced by B. megaterium J-65 was identified as homopolymer of 3-hydoxybutyric acid by GC and NMR.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.363-368
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• 2017

Methylotrophy is able to use reduced one-carbon compound, such as methanol and methylamine, as a sole carbon source. Methylobacterium extorquens AM1 is the most extensively studied methylotroph utilizing serine-isocitrate lyase cycle. Because the Poly 3-hydroxybutyrate (PHB) synthesis pathway in M. extorquens AM1 is likely to interlink with EMCP (ethylmalonyl-CoA pathway), glyoxylate, and TCA cycles, regulation of PHB production is needed to produce EMCP-derived acid or TCA acids. To adjust carbon flux to PHB production, PhaR, which seems to have function of regulator of PHB synthesis and acetyl-CoA flux, was knocked out in M. extorquens AM1 by using markerless gene deletion methods. As a result, PHB granules were remarkably reduced in the knockout strain ${\Delta}phaR$ compared to parental strain. Although lag phase was extended for 12h, ${\Delta}phaR$ showed similar cell growth and methanol consumption rate compared to wild type.

• KSBB Journal
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• v.11 no.2
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• pp.246-253
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• 1996

An obligatory methanotroph Methylosinus trichosporium OB3b was cultivated for the production of poly-${\beta}$-hydroxybutyric acid(PHB) in shake-flask using liquefied natural gas(LNG) as the sole source of carbon and energy. The maximal specific growth rate decreased by 40% using LNG compared with that obtained with pure methane. This is attributed to the inhibition by ethane and propane presents in the LNG as impurities. For the production of PHB, two-stage culture separating the production stage from the growth stage was carried out. PHB accumulation was observed after switching nutrient-sufficient to nutrient-limited condition of non-carboneous component (NO3-, PO43-, K+, Na+, Fe2+, or Mg2+). The limitation of K+ or Mg2+ resulted in relatively high PHB content, but the highest content was obtained by nitrate limitation. The optimal pH and temperature for PHB accumulation was 7.0 and $30^{\circ}C$. Under the optimal condition the maximal PHB content was about 45% after 4-day cultivation.

• KSBB Journal
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• v.13 no.1
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• pp.96-100
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• 1998

Two promoters (trc and P$\rho$) were inserted in PHA operon derived from Alcaligenes eutrophus to obtain high chain molecules of polyhydroxybutyrate (PHB) in recombinant Escherichia coli. Newly designed PHA operon was used to control the gene expressions of hydroxybutyric CoA and PHA polymerization, separately. Plasmids containing new synthetic operon was transformed into E. coli DH5$\alpha$ and analyzed for PHB production. Without induction of the PHA biosynthetic operon, PHA synthase which has low activity might supply low concentration of initiator during the polymerization reaction, resulting very high molecular weight of polymer. An increase of PHB average molecular weight was observed with decreased IPTG (isopropyl $\beta$ -Dithiogalactosidase) concentration. When no IPTG was added to the culture of E. coli DH5$\alpha$ /$\rho$ SJS1 which contained two promoters in PHA operon, high chain polymer having an average molecular weight of $2.5{\times}10^7$ was achieved. Analysis of the enzyme activities of PHA biosynthetic enzymes suggests that PHA synthase, the enzyme responsible for polymerizing 3-hydroxybutyric CoA, controls the molecular weight of PHB produced in vivo.

• Microbiology and Biotechnology Letters
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• v.19 no.2
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• pp.186-192
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• 1991

It is very important to have a good kinetic model which considers the effects of both ammonium and glucose for the control and optimization of the poly-${\beta}$-hydroxybutyrate (PHB) fermentation. A kinetic model for the growth of Alcaligenes eutrophus and the biosynthesis of PHB under both ammonium and glucose limitation was proposed. Growth rate of residual biomass was expressed as a function of concentrations of residual biomass, glucose and ammonium having glucose inhibition. PHB production rate was expressed as a function of concentrations of residual biomass, glucose, ammonium and PHB content having ammonium and product inhibitions. Novel approaches were made to estimate the parameters in the model equations which considered two limiting substrates. Model parameters were evaluated by graphical and simplex methods. The proposed kinetic model fitted the data very well.