High rate heptanoate production from propionate and ethanol using chain elongation

Heptanoate (or enanthate), a saturated mono-carboxylate with seven carbon atoms, is a commercially produced biochemical building block with versatile applications. Currently, heptanoate is mainly derived from the oxidation of heptaldehyde, which can be obtained after pyrolysis of castor oil. The objective of this investigation was to achieve efficient high rate heptanoate production using a mixed culture chain elongation process based on propionate and ethanol. An efficient high rate heptanoate production using chain elongation could offer an alternative for heptanoate production from castor oil. The investigation was performed in an upflow anaerobic filter with a hydraulic retention time of 17 h. A heptanoate production rate of 4.5 g l-1 d-1 was achieved with a heptanoate concentration of 3.2 g l-1. These results show sufficient potential to consider this approach as an alternative for heptanoate production from castor oil. Future research should make heptanoate production from propionate and ethanol more cost-effective.