Fed-batch production of unsaturated medium-chain-length polyhydroxyalkanoates with controlled composition by Pseudomonas putida KT2440 |
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Authors: | Zhiyong Sun Juliana A. Ramsay Martin Guay Bruce A. Ramsay |
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Affiliation: | (1) Chemical Engineering, Queen’s University, Kingston, Ontario, Canada;(2) Polyferm Canada, 4530 CamdenE-Portland Bdry Rd, RR1 Harrowsmith, Ontario, K0H 1V0, Canada |
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Abstract: | 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, fed-batch 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. |
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Keywords: | MCL-PHA Unsaturated Fed-batch Fermentation Pseudomonas putida |
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