Polyester Biosynthesis Characteristics of Pseudomonas citronellolis Grown on Various Carbon Sources, Including 3-Methyl-Branched Substrates

AUTOR(ES)

Choi, Mun Hwan

RESUMO

Forty-two different carbon sources were tested for the polyester synthesis of a citronellol-utilizing bacterium, Pseudomonas citronellolis (ATCC 13674). These included linear C2 to C10 monocarboxylic acids, C3 to C10 dicarboxylic acids, saccharides, α,ω-diols, hydrocarbons, and 3-methyl-branched substrates such as 3,7-dimethyl-6-octen-1-ol (citronellol), 3-methyl-n-valerate, 3-methyl-1-butanol, and 3-methyladipate. Isolated polymers were characterized by gas chromatography, infrared spectroscopy, 1H- or 13C-nuclear magnetic resonance spectroscopy, 1H-13C heteronuclear correlation spectroscopy (1H-13C COSY), 1H-1H homonuclear COSY, and differential scanning calorimetry. Polyesters from nine monocarboxylic acids and two related carbon sources could be metabolically divided into three groups. The first group of C2 to C4 carbon sources resulted in copolyesters composed of 61 to 70 mol% 3-hydroxydecanoate, 23 to 33 mol% 3-hydroxyoctanoate, 3.6 to 9.0 mol% 3-hydroxy-5-cis-dodecenoate, and 1.8 to 2.6 mol% 3-hydroxy-7-cis-tetradecenoate. Carbon sources in group II (C7 to C10) produced copolyesters composed of 3-hydroxyacid monomer units with the same number of carbon atoms as the substrate (major constituent) and monomer units with either two less or two more carbons. Negligible amounts of 3-hydroxy-5-cis-dodecenoate and 3-hydroxy-7-cis-tetradecenoate were detected in copolyesters from this group. Copolyesters from group III (C5 and C6) had a monomer unit distribution that could be said to be between those of groups I and II. In addition, a novel copolyester, poly(3-hydroxy-7-methyl-6-octenoate-co-3-hydroxy-5-methylhexanoate), was synthesized when grown on citronellol. The 1H-13C heteronuclear COSY spectrum for monomer unit II revealed that both methylene and isopropyl groups, proximately connected in series to a single chiral center, had magnetically diastereotopic natures.

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