High rate heptanoate production from propionate and ethanol using chain elongation

► Heptanoate production rate from propionate was improved by more than 25 times. ► Obtained heptanoate concentrations higher than heptanoic acid solubility in water. ► Limited heptanoate selectivity mainly due to caproate and valerate production. ► A higher ethanol load increased heptanoate, caproate and propanol production. ► First time that traces of pelargonate were measured during chain elongation.