This is the first report of the use of decanoic acid as the primary substrate for MCL-PHA production in fed-batch fermentation. It was found that acetic acid could be mixed with decanoic acid to prevent its crystallization and that its presence led to more decanoic acid being directed to polymer synthesis. The co-feeding approach allowed YPHA/DA yields of around 0.9 g g−1 to be achieved. Higher yields are not obtainable unless oxidation is curtailed through inhibiting (Jiang et al., 2012) or knocking-out key enzymes (Wanget al., 2011) two approaches that we are currently studying.By applying a two-stage feeding strategy (exponential followed by linear feeding), the performance was further improved, producing 75 g L−1 of biomass containing 74% of PHA. The MCL-PHA composition was not significantly affected by either the substrate feeding ratio or feeding rate. Further optimization of the feeding regime will undoubtedly further improve productivity and final PHA concentration