Bacterial Poly(3-hydroxyalkanoates) Bearing Carbon−Carbon Triple Bonds

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Abstract
Production of poly(3-hydroxyalkanoates), PHAs, by Pseudomonas oleovorans (P. oleovorans) and Pseudomonas putida (P. putida) grown with mixtures of nonanoic acid, NA, and 10-undecynoic acid, 10-UND(≡), were investigated. Both microorganisms produced PHAs containing carbon−carbon triple bonds in fractions from 0 to 100%, depending on the composition of the carbon substrate mixture. The amounts of unsaturated repeating units in PHAs produced by P. oleovorans were higher than those in PHAs produced by P. putida grown with the same carbon substrates. The repeating units containing carbon−carbon triple bonds were 3-hydroxy-8-nonynoate, 3HN(⋮), and 3-hydroxy-10-undecynoate, 3HUD(⋮). 3HN(⋮) was the major repeating unit formed from 10-UND(⋮). The relative amounts of 3HN(⋮) and 3HUD(⋮) in PHAs produced by P. putida were slightly different from those in PHAs produced by P. oleovorans. The number average molecular weights of PHAs produced in this study were approximately 50 000, and polydispersity indices were approximately 2.5 as determined by gel permeation chromatography. The molecular weight distribution and the relative amounts of 3HN(⋮) and 3HUD(⋮) were not affected by either growth time or the composition of the carbon substrate. PHAs bearing triple bonds were soft and differential scanning calorimetry thermograms of these polymers showed very small melting endotherms at approximately 60 °C. The glass transition temperatures were in the range of −33 to −21 °C.