Interest in the production of carboxylic acids from organic waste has grown due to their high economic value as platform precursors in the production of pharmaceuticals, industrial chemicals, bioplastics, and more. This study focuses on assessing chain elongation potential from different inoculum sources. Microbial communities from two different anaerobic digesters, treating a mixture of manure, straw, and food waste in lab-scale, as well as digestate taken from a full-scale plant with food waste as the main substrate, were inoculated in 300 mL bottles. Different combinations of electron donors (i.e., ethanol and lactic acid) and electron acceptor (i.e., acetic acid) were used as substrates for microbial chain elongation. The microbial culture was enriched through subsequent dilution and re-inoculation using the optimum ratios of electron donors and acceptor based on the yields of caproic acid. The highest caproic acid production was observed in the presence of BES, ethanol, and acetic acid by the inoculum from the lab-scale digesters, reaching up to 72 – 74% of the theoretical potential of added electron donor. The inoculum from the full-scale digested food waste had a maximum caproic acid production of 11% of the theoretical potential of added electron donor in the presence of BES, lactic acid, and acetic acid. The subsequent enrichment of inoculum from the anaerobic digesters resulted in an increase in the caproic acid concentration by up to 40 mM (4.6 g/L). These results underscore the importance of inoculum source and electron donor selection in chain elongation, while highlighting sequential enrichment as an effective strategy for tailoring microbial communities to trigger both even and odd carbon chain elongation to produce caproic and heptanoic acids.