Fed-batch production of unsaturated medium-chain-length polyhydroxyalkanoates with controlled composition by Pseudomonas putida KT2440 (original) (raw)

Unsaturated medium-chain-length polyhydroxyalkanoates (MCL-PHA) were produced at a productivity of 0.63-1.09 g PHA l −1 h −1 with final PHA content ranging from 42.6 to 55.8% in single-stage, carbon-limited, fedbatch fermentations of Pseudomonas putida KT2440. A mixture of nonanoic acid (NA) and 10-undecenoic acid (UDA =) was fed exponentially to control growth rate. Varying the specific growth rate (0.14 h −1 vs. 0.23 h −1) at similar substrate feed ratios (NA:UDA = =5:1) had little effect on the final PHA content and relative composition. However, decreasing the NA:UDA = ratio decreased the final amount of PHA produced from 56% with NA:UDA = = 5.07:1 to only 42% at NA:UDA = =2.47:1. The molar fraction of all 3-hydroxyalkanoate monomers in the PHA product was relatively constant throughout each fermentation, indicating that the final product was homogeneous rather than a mixture of different copolymers. A linear relationship between unsaturation of the PHA produced and unsaturation of the carbon feed was found, which demonstrates the feasibility of producing unsaturated MCL-PHAs with controlled polymeric composition in a fed-batch process.