Enhanced yield of medium-chain-length polyhydroxyalkanoates from nonanoic acid by co-feeding glucose in carbon-limited, fed-batch culture.

Medium-chain-length polyhydroxyalkanoates (MCL-PHAs) were produced in carbon-limited, single-stage, fed-batch fermentations of Pseudomonas putida KT2440 by co-feeding nonanoic acid (NA) and glucose (G) to enhance the yield of PHA from NA. An exponential (mu=0.25 h(-1)) followed by a linear feeding strategy at a NA:G ratio of 1:1 (w/w) achieved 71 g l(-1) biomass containing 56% PHA. Although the same overall PHA productivity (1.44 g l(-1) h(-1)) was obtained when NA alone was fed at the same specific growth rate, the overall yield of PHA from NA increased by 25% (0.66 g PHA g NA(-1) versus 0.53 g g(-1)) with glucose co-feeding. Further increasing glucose in the feed (NA:G=1:1.5) resulted in a slightly higher yield (0.69 g PHA g NA(-1)) but lower PHA content (48%) and productivity (1.16 g l(-1) h(-1)). There was very little change in the PHA composition.