• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1217-1226
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• 2004

A psychrotrophic bacterial strain, Pseudomonas fluorescens BM07, synthesized unsaturated fatty acids (UFA) from fructose in response to lowering of growth temperature, and incorporated them into both polyhydroxyalkanoic acid (PHA) and membrane lipid. The blocking of PHA synthesis by adding 5 mM 2-bromooctanoic acid to the growth medium, containing 70 mM fructose, was found to be a useful means to profile the composition of membrane lipid by gas chromatography. As the growth temperature changed from 35 to $50^{\circ}C$, the total content of two UFA, 3-hydroxy-cis-5­dodecenoic acid ($C_{12:1}$) and 3-hydroxy-cis-7-tetradecenoic acid ($C_{14:1}$), in PHA increased from 31 to 44 $mol\%$. The growth at lower temperatures also led to an increase in the level of two major UFA, palmitoleic acid (C16:1 cis9) and cis-vaccenic acid (C18:1 cis11), in membrane lipid. A fraction of these membrane-lipid UFA was converted to their corresponding cyclopropane fatty acids (CFA). The CFA conversion was a function of culture time, exhibiting biphasic increase before and after entering the stationary phase. However, pH changes in growth media had no effect on the CFA conversion, which is contrary to the case of E. coli reported. The cells grown at $30^{\circ}C$ responded to a cold shock (lowering the medium temperature down to $10^{\circ}C$) by increasing the level of C16:1 cis9 and C 18: I cis II up to that of $10^{\circ}C$-grown control cells and concomitantly decreasing the relative level of cis-9,10­methylenehexadecanoic acid (the CFA converted from C16:1 cis9) from 14 to 8 $mol\%$, whereas the 10-grown cells exhibited little change in the lipid composition when exposed to a warmer environment of $30^{\circ}C$ for 12 h. Based on this one- way response, we suggest that this psychrotrophic strain responds more efficiently and sensitively to a cold shock than to a hot shock. It is also suggested that BM07 strain is a good producer of two unsaturated 3-hydroxyacids, $C_{12:1}\;and\;C_{141:1}$.

• Journal of Microbiology and Biotechnology
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• v.12 no.3
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• pp.518-521
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• 2002

Poly(3-hydroxyalkanoate) copolyesters containing both carbon-carbon double and carbon-carbon triple bonds were produced by Pseudomonas oleovorans grown in mixtures of 10-undecynoic acid (10-UND($\equiv$)) and 10-undecenoic acid (10-UND(=)). The PHA content in the dry cells was usually 40 wt%. The bioconversion yield of ($10-UND({\equiv})$) to PHA by P. oleovorans was remarkably enhanced from 1% to over 24% as the fraction of 10-UND(=) in the carbon substrate mixtures increased from 0 to 50%. These values were higher than those obtained when P. oleovorans was grown in the same molar mixtures of ($10-UND({\equiv})$) and nonanoic acid (NA), indicating that 10-UND(=) was more efficient than NA as a cosubstrate in inducing cometabolic PHA production.

• Journal of Microbiology and Biotechnology
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• v.13 no.1
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• pp.64-69
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• 2003

Pseudomonas chlororaphis HS21 was isolated from a soil sample and found to produce medium-chain-length polyhydroxyalkanoates (MCL-PHAs) using palm kernel oil (PKO) as the sole carbon source. Up to 3.3 g/1 dry cell weight containing $45\%$ MCL-PHA was produced, when the strain was grown for 21 h in a jar fermentor culture containing 5 g/1 PKO. The polymer produced from PKO consisted of unsaturated monomers of $7.3\%$ 3-hydroxy-5-cis-tetradecenoate and $2.3\%$ 3-hydroxy-5,8,-cis, cis-tetradecadienoate as well as saturated even-carbon number monomers ranging from $C_6\;to\;C_14$, as determined by GC and El GC/MS The PHA was a transparent, sticky material at room temperature. A differential scanning calorimetric analysis revealed that the polymer was amorphous with a $-44^{\circ}C$ glass transition temperature. The number average molecular weight and polydispersity index of the PHA were 83,000 and 1.53, respectively. Although the PHA was practically biodegradable, its degradability was lower than that of poly(3-hydroxyoctanoate) based on a comp:trison of the clear zones formed by growing PHA depolymerase-producing bacteria on an agar plate containing the respective polymers.

• Korean Journal of Microbiology
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• v.41 no.3
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• pp.225-231
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• 2005

The characteristics of cell growth and medium-chain-length polyhydroxyalkanoate (MCL-PHA) biosynthesis of Pseudomonas chlororaphis HS21 were investigated using plant oils as the carbon substrate. The organism was efficiently capable of utilizing plant oils, such as palm oil, corn oil, and sunflower oil, as the sole carbon source for growth and MCL-PHA production. When palm oil (5 g/L) was used as the carbon source, the cell growth and MCL-PHA accumulation of this organism occurred simultaneously, and a high dry cell weight (2.4 g/L) and MCL-PHA ($40.2\;mol{\%}$ of dry cell weight) was achieved after 30 hr of batch-fermentation. The repeating unit in the MCL-PHA produced from palm oil composed of 3-hydroxyhexanoate ($7.0\;mol{\%}$), 3-hydroxyoctanoate ($45.3\;mol{\%}$), 3-hydroxydecanoate ($39.0\;mol{\%}$), 3-hydroxydodecanoate ($6.8\;mol{\%}$), and 3-hydroxytetradecanoate ($1.9\;mol{\%}$), as determined by GC/MS. Even though glucose was a carbon substrate that support cell growth but not PHA production, the conversion rate of palm oil to PHA was significantly increased when glucose was fed as a cosubstrate, suggesting that bioconversion of some functionalized carbon substrates to related polymers in P chlororaphis HS21 could be enhanced by the co-feed of good carbon substrates for cell growth. In addition, the change of compositions of repeating units in MCL-PHAs synthesized from the plant oils was markedly affected by the supplementation of acrylic acid, an inhibitor of fatty acid ${\beta}-oxidation$. The addition of acrylic acid resulted in the increase of longer chain-length repeating units, such as 3-hydroxydodecanoate and 3-hydroxytetradecanoate, in the MCL-PHAs produced. Particularly, MCI-PHAs containing high amounts of unsaturated repeating units could be produced when sunflower oil and corn oil were used as the carbon substrate. These results suggested that the alteration of PHA synthesis pathway by acrylic acid addition can offer the opportunity to design new functional MCL-PHAs and other unusual polyesters that have unique physico-chemical properties.

• Korean Journal of Microbiology
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• v.36 no.2
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• pp.84-90
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• 2000

Biodegradation of vanous medium-chain-length polyhydroxyalkanoates (MCL-PHAs) by an extracellular depolymerase system from Pseudomonas sp. RY-1 was investigated under laboratoly conditions. The degradation rate of the polymers was determined by quantitative clem zone technique, enzyme (turbidity) assay, and respirometry assay. Although the enzyme system secreted by Pscudomor~as sp. RY-1 was capable of degrading all MCL-PHAs tested. its secretion was influenced by the availability of secondary carbon sources. The rate of enzymatic degradation of MCL-PHAs was dependent upou the monomeric composition of the polyesters and reduced as the chain lengths of the monomer m t s in the polyesters increased. MCL-PHAs containing C-even monomer units showed faster degradation rate than MCL-PHAs containing C-odd monomer units. Respiration rates of MCL-PHAs with C-even monomer uuts were also much faster than those of MCL-PHAs with C-odd monomer units. The degmdation rate of MCL-PHAs bearing unsaturated substituents was faster than that of mcl-PHAs without functional substituents, which is suggesting the correlation between the degradation rate and the crystallinity of MCL-PHAs.