• Journal of Microbiology and Biotechnology
• /
• v.6 no.2
• /
• pp.147-149
• /
• 1996

Poly(3-hydroxybutyrate) (PHB) was synthesized and accumulated intracellularly to a high concentration (7 g/l) by cultivating recombinant Escherichia coli XL1-Blue (pSYLl05) in a complex medium containing 20 g/l glucose. The morphology of PHB granules was examined by transmission electron microscopy. The PHB granules synthesized in recombinant E. coli were much larger than reported values for wild type microorganisms, and were often irregularly shaped. Some cells were apparently extruding PHB into the medium, which suggests that PHB granules maintain some fluidity and cells become fragile due to PHB accumulation.

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

• Korean Journal of Environmental Biology
• /
• v.17 no.3
• /
• pp.249-255
• /
• 1999

The effect of surface roughness on biodegradability of poly (3-hydroxybutyrate) was investigated. The PHB film prepared by cooling the molten polymer slowly ($-0.5^{\circ}C$/min) had higher crystallinity and melting temperature than that prepared by quenching into liquid nitrogen followed by annealing at $90^{\circ}C$ for 2 hours. However, the former sample was found to degrade faster than the latter due to presence of microscopic crack. Roughening the surface of a PHB film by hot pressing under a coarse surfaced plate accelerated the bioerosion considerably of the sample in comparison with the sample having the same thermal history but smooth surface.

• Textile Coloration and Finishing
• /
• v.30 no.2
• /
• pp.130-140
• /
• 2018

In the bio-synthesis of poly(3-hydroxybutyrate)(PHB), which is a kind of poly(3-hydroxyalkanoate)(PHA), aimed to control the low molecular weight of PHB and obtain a telechelic PHB. As a result of incubation of R. eutropha at $30^{\circ}C$ with ethylene glycol added as a chain transfer agent, PHB content on the dry cell weight increased up to 24h, however, it decreased after that, and the molecular weight of PHB increased from 9h to 12h, and then, decreased up to 72h. The decrease of the content and the molecular weight of PHB indicates that PHB was decomposed as an energy source in bacterial cells and was incorporated into metabolic pathways. $^1H-NMR$ of the obtained PHB after incubation for 72h was measured to determine the terminal groups of the PHB during incubation. As the results of $^1H-NMR$ measurement, the peaks derived from ethylene glycol in both terminals of PHB were observed. Which indicate that the terminal reaction was caused by the addition of ethylene glycol, and that telechelic PHB having hydroxyl group at the both terminals where molecular weight was controlled was successfully synthesized.

• Fibers and Polymers
• /
• v.4 no.4
• /
• pp.195-198
• /
• 2003

Epoxidized polybutadiene (EPB) was prepared by polybutadiene (PB) with m-chloroperbenzoic acid (MCPBA) in homogeneous solution. EPB was blended with poly(3-hydroxybutyrate) (PHB) up to 30 wt% by solution-precipitation procedure. The thermal decomposition of PHB/EPB blends was studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The thermograms of PHB/EPB blends contained a two-step degradation process, while that of pure PHB sample exhibited only one-step degradation process. This degradation behavior of PHB/EPB blends, which have a higher thermal stability as measured by maximum decomposition temperature and residual weight, is probably due to crosslinking reactions of the epoxide groups in the EPB component with the carboxyl chain ends of PHB fragments during the degradation process, and the occurrence of such reactions can be assigned to the exothermic peaks in their DTA thermograms.

• The Korean Journal of Mycology
• /
• v.23 no.4 s.75
• /
• pp.348-353
• /
• 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 Microbiology and Biotechnology
• /
• v.10 no.5
• /
• pp.628-631
• /
• 2000

The timing of poly(3-Hydroxybutyrate) (PHB) biosynthesis was controlled by varying the agitation speed of a stirred tank fermentor during the pH-stat fed-batch culture of recombinant Escherichia coli strain GCSC 6576 harboring pSYL107. Using a concentrated whey solution containing ca. 200 g/l lactose as the nutrient feed, the PHB content was only 57% after 35h due to volumetric limitation of the fermentor. However, by limiting the oxygen by maintaining the agitation speed at 300 rpm, the final PHB content increased to 70% after 70h with a cell concentration of 15 g/l. When the agitation speed was increased up to 500 rpm, a cell concentration of 31 g/l with 80% PHB was obtained after 52h. A further increase in the maximum agitation speed increased the cell concentration, PHB concentration, and PHB productivity, however, the PHB content decreased to 56-58%.

• Journal of Microbiology
• /
• v.40 no.2
• /
• pp.129-133
• /
• 2002

The fungus, Emericellopsis minima W2, capable of degrading poly(3-hydroxybutyrate) (PHB) was isolated from a waste water sample. Production of the PHB depolymerase from E. minima W2 (PhaZ/ sub Emi/) was significantly repressed in the presence of glucose. PhaZ/ sub Emi/ was purified by column chromatography on Octyl-Sepharose CL-4B and Sephadex G-100. The molecular mass of the PhaZ/ sub Emi/), which consisted of a single polypeptide chain, was estimated to be 48.0 kDa by SDS-PAGE and its pI vague was 4.4. The maximum activity of the PhaZ/ sub Emi/ was observed at pH 9.0 and 55$\^{C}$. It was significantly inactivated by 1mM dithiothreitol, 2mM diisopropyl fluorphosphate, 0.1mM Tween 80, and 0.1 mM Triton X-l00, but insensitive to phenylmethylsulfonyl fluoride and N-ethylmaleimide. The PhaZ/ sub Emi/ efficiently hydrolyzed PHB and its copolyester with 30 mol% 3-hydroxyvalerate, but did not act on poly(3-hydroxyoctanoate). It also hydrolyzed p-nitrophenylacetate and p-nitrophenylbutyrate but hardly affected the longer-chain forms. The main hydrolysis product of PHB was identified as a dimer of 3-hydroxybutyrate.

• Korean Journal of Microbiology
• /
• v.37 no.1
• /
• pp.92-99
• /
• 2001

High-cell-density cultivation of Ralstonia eutopha KHB 8862 by fed-batch fermentation in a 200 l pilot plant was carried out for the mass production of poly(3-hydroxybutyrate) (PHB). After 80 h of cultivation, the dry cell weight (DCW), PHB concentration, and PHB yield from fructose syrup reached 168 g/l, 74%DCW, and 0.27 (w/w), respectively, resulting in a productivity of 1.6 g of PHB/L/h. Based on these results, the PHB production cost from bacterial fermentation was analyzed and economic evaluation was performed. In the case of new investment being implemented or not, the production cost of PHB was US$ 3.15/kg and US$ 2.41/kg, respectively. PHB productivity and PHB yield on a carbon substrate were both important factors to be optimized. The increase of PHB yield on a carbon sources significantly decreased the PHB production cost but the increase in productivity had a relatively slight effect on the decrease in PHB production cost because the cost of carbon sources (37%) for PHB was larger in proportion to total cost than the depreciation cost (17%). These results suggest that the increased PHB yield from carbon sources and the development of new cheaper substrates would be more effective in decreasing PHB production cost than the increase in productivity. It was demonstrated that PHB is not in competition with consumable plastics such as PET in present market. Therefore, it is essential to lower production cost to be used as a bulk product and desirable to develop new application fields for PHB such as biomedical and cosmeceuticals.

• Microbiology and Biotechnology Letters
• /
• v.26 no.3
• /
• pp.206-212
• /
• 1998

The effects of the pretreatment with coagulants on the recovery efficiency of poly (3-hydroxybutyrate, PHB) synthesized in Alcaligenes eutrophus were investigated. Al-base or Fe-base coagulants, and the dispersion method of 30% hypochlorite solution and chloroform were used as coagulants and PHB recovery method, respectively The recovery efficiency of PHB from the cells harvested with Al-base coagulants at the range from 0 to 1000 mg-Al/L was similar to that from cells harvested without the coagulants. At these conditions, the concentrations of residual aluminium in the purified PHB were below 250 mg-Al/kg-PHB, indicating the effect of residual aluminum on the characteristics of the purified PHB can be insignificant. When the dosage of coagulants was over 1000 mg-Al/L, the PHB recovery remarkably decreased with increasing the coagulant dosage. However, the PHB recovery could be enhanced by the use of 50% hypochlorite solution instead of 30% hypochlorite solution. Even though the reduction of PHB recovery efficiency was not found by using Fe-base coagulants, the purified PHB was stained pale red due to residual iron, These results suggest that the use of Al-base coagulants did not exert bad influence on neither PHB recovery efficiency and PHB purity.