- Biosynthesis of polyhydroxybutyrate and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by bacillus thuringiensis R-510
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Park, Sang Kyu , Lee, Kang Tae , Kim, Young Baek , Rhee, Young Ha
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J. Microbiol. 1997;35(2):127-133.
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 Abstract
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Biosynthesis of polyhydroxybutyrate and copolymer consisting of 3-hydroxybutyrate and 3-hydroxyvalerate [poly(3HB-co-3HV)] by Bacillus thuringiensis R-510 grown with glucose or with mixtures of glucose and propionate was investigated. n-Alkanoic acids other than propionate were not precursors of 3HV units. The fraction of 3HV unit in the copolymer increased from 0 to 84 mol% of 3HV. Polymer yield decreased as the fraction of propionate was increased but the molecular weight distribution was not affected by the composition of carbon substrate. The minimum melting temperature (around 65℃) of poly (3HB-co-3HV) copolymers was observed for the polymer bearing approximately 35 mol% of 3HV. Polyhydroxyalkanoates production by this organism was not dependent on nutritional limitation, but remarkably influenced by dissolved oxygen concentration in the culture medium. Low level of dissolved oxygen concentration prevented spore formation in the cells and stimulated the synthesis of polyhydroxyalkanoate. The composition of poly (3HB-co-3HV) produced by B. thuringiensis R-510 lyhydroxyalkanoate. The composition of poly(3HB-co-3HV) produced by B. thuringiensis R-510 varied according to the growth time. However, there was no evidence that polymers isolated from cells were mixtures of immiscible polymers.
- Culture conditions affecting the molecular weight distribution of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesized by alcaligenaes sp. SH-69
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Yoon, Joo Seok , Park, Sang Kyu , Kim, Young Baek , Maeng, Hack Young , Rhee, Young Ha
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J. Microbiol. 1996;34(3):279-283.
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The weight average molecular weight of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesized by Alcaligenes sp. SH-69 was altered between 3.2 × 10^5 and 1.1 × 10^6 depending upon various culture conditions. It appeared that culture conditions favorable for the efficient production of copolyesters promoted the formation of higher molecular weight copolyesters. Polydispersity indices of isolated copolyesters were in the range of 1.5 to 2.5.
- Biosynthesis of Poly-β-Hydrozyalkanoates by Bacillus thuringiensis R-510
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Lee, Kang Tae , Kim, Jeong Yoon , Rhee, young Ha , Bae, Kyung Sook , Kim, Young Baek
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J. Microbiol. 1995;33(1):59-65.
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Synthesis and accumulation of Poly-β-Hydrozyalkanoates (PHA) in Bacillus thuringiensis R-510 isolated from soil were investigatd. This organism was resistant to relatively higj concentration of propionate and had a capability of accumulatinf copolymers consisting of 3-hydroxybutyrate(3HB) and 3-hydroxyvalerate(3HV) when the medium was supplemented with propionate as a precursor, The PHA content maximally reached up to 44.5% of dry cell weight in the presence of 0.1% propionate. The molar fraction of 3HV in the copolymer was increased from 19.4 to 80,2 mol% by adding 0.05 to 0.5% propionate to glucose medium. The addition of propionate during exponential or stationary phase of cell growth was less effective for the enhancement of 3HV content in the copolymer, although cell mass and PHA content were not affected by the time of propionate addition. PHB homopolymer and copolymer produced by B. thuringiensis R-510 were measured to have number average molecular weights in the range of 53,000 to 65,000. Polydispersity indices were between 1.5 and 2.2. Some of the produced polymers had bimodal molecular weight distribution.
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