Fig. 3. Metabolites during microbial chain elongation in soils initially fed with 100 mM ethanol and subjected to semi-batch enrichment.

A semi-batch cycle consisted of removing one third of microcosm liquid (25 mL) and replacing with 25 mL medium containing 100 mM ethanol. The incubation time for each cycle (between 6–43 days) is shown in Table 2. The plotted carboxylates and alcohols are final measured metabolite concentrations at the end of each cycle before liquid was removed and medium with substrates was readded. The data are averages with standard deviation of duplicate microcosms.