Biosynthesis of polyhydroxyalkanoate copolyester containing cyclohexyl groups by Pseudomonas oleovorans

Production of polyhydroxyalkanoates (PHAs) substituted with cyclohexyl grou ps by Pseudomonas oleovorans grown with 4-cyclohexylbutyric acid (4-CHB) an d its mixtures with nonanoic acid (NA) was investigated. Addition of NA to medium gave rise to an increase in the total concentration of 3-hydroxy-4-c yclohexylbutyrate repeating unit in the PHAs, indicating that the bioconver sion rate of 4-CHB to polyester was significantly improved by the cometabol ic effect. Increasing the proportion of NA from 1.0 to 7.5 mM at a concentr ation of 10 mM total carbon substrate also accelerated the uptake speed of 4-CHB by the organism and resulted in an increase of the ratio of 3-hydroxy nonanoate to 3-hydroxyheptanoate from 1.28 to 2.05. Differential scanning c alorimetric analysis of the PHAs bearing the corresponding functional group s showed one melting transition and one glass transition temperature varyin g according to the composition. These results indicated that random copolye sters were obtained from the carbon substrates used in this study. (C) 2001 Elsevier Science BN. All rights reserved.