Untangling the role of facultative bacteria in LCFA conversion to methane

Abstract

[Excerpt] Palmitate accumulation is frequently reported in continuous methanogenic bioreactors fed with lipidrich wastewater, and facultative bacteria were suggested to be involved in this conversion. In this work, the possible effects of limited oxygen conditions in triggering palmitate formation from oleate were studied. Two bioreactors were operated in parallel, one under strict anaerobic conditions (AnR) and the other with the feeding tank open to the air (FR). Palmitate was the main LCFA in both reactors, but it reached approximately 7 times higher concentrations in the FR than in the AnR (16 and 2 g·L-1 in COD, respectively). Moreover, oleate was more abundant in the AnR than in the FR, presenting concentrations of 1.3 and 0.5 g·L-1, and oxidation-reduction potential values (ORP) of -366 mV and -255 mV were measured. [...]