Decanoic acid is an ideal substrate for the synthesis of medium-chain-length poly-3-hydroxyalkanoate
(MCL-PHA), but its use for this purpose has only previously been studied in shake-flasks likely due to its
surfactant properties, low aqueous solubility and high melting temperature. A fed-batch fermentation
process was developed for the production of MCL-PHA from decanoic acid using Pseudomonas putida
KT2440. Decanoic acid was kept in liquid form by heating or by mixing with acetic acid to prevent
crystallization. Different ratios of decanoic acid:acetic acid:glucose (DA:AA:G) were fed to produce a
specific growth rate of 0.15 h−1. This method produced a maximum of 39 g L−1 dry biomass containing
67% MCL-PHA when the DA:AA:G ratio was 5:1:4. However, a declining growth rate occurred in the late
stage of fermentation, resulting in decanoic acid accumulation in the bioreactor leading to foaming. The
duration of MCL-PHA production was extended by shifting from exponential to linear feeding before
accumulation of decanoic acid. This resulted in 75 g L−1 biomass containing 74% PHA and an overall PHA
productivity of 1.16 g L−1 h−1 with the production of each gram of PHA requiring only 1.16 g of decanoic
acid. Thefinal PHAcomposition (on amolar basis) was 78%3-hydroxydecanoate, 11%3-hydroxyoctanoate
and 11% 3-hydroxyhexanoate.