PHAs produced by Pseudomonas putida and Pseudomonas oleovorans grown with n-alkanoic acids containing aromatic groups

摘要

Poly(3-hydroxyalkanoates), PHAs, bearing aromatic groups were biosynthesized by Pseudomonas putida and Pseudomonas oleovorans grown with various carbon substrates such as 5-phenylvaleric acid, 5PVA, 8-(p-methylphenoxy)octanoic acid, 8pMPO, 6-(p-methylphenoxy)hexanoic acid, 6pMPH, 8-(m-methylphenoxy)octanoic acid, 8mMPO, 8-(o-methylphenoxy)octanoic acid, 8oMPO, and 11-(p-methylphenoxy)undecanoic acid, 11pMPU. 11pMPU and 8oMPO did not support PHA production by both P. oleovorans and P. putida while other carbon substrates supported PHA production. PHAs obtained from 8-(methylphenoxy)octanoic acids contained 3-hydroxy-4-methylphenoxybutyrate and 3-hydroxy-6-methylphenoxyhexanoate units. DSC and X-ray scattering analysis indicated that PHAs biosynthesized from 5PVA and 8mMPO were amorphous while the PHA biosynthesized from 8pMPO was crystalline. PHAs biosynthesized by P. putida grown with mixtures of nonanoic acid, NA, and either 5PVA or 8pMPO were fractionated into two fractions on the basis of the solubility in n-hexane. The n-hexane insoluble fractions were examined to find that these polymers were random copolymers containing repeating units produced from both carbon substrates. Results in this study showed P. putida produced random copolymers as long as this microorganism utilized both carbon substrates. The compositions of the copolymers were dependent on the nature of carbon substrates. DSC analysis showed that PHAs from 8pMPO and from 5PVA were miscible in each other. The number-average molecular weight of the PHA from 8pMPO was 25 000 while those of PHAs from NA and 5PVA were 50 000 as determined by gel permeation chromatography. The polydispersity indices were approximately 2.5 regardless of the carbon substrate.