Community profile governs substrate competition in polyhydroxyalkanoate (PHA)-producing mixed cultures.

• Acetate and propionate uptakes were inhibited in the presence of butyrate and valerate. • Higher abundance of Plasticicumulans led to a more significant inhibitory effect. • HB:HV ratio was close to theoretical value in Plasticicumulans- dominating cultures. Polyhydroxyalkanoates (PHAs) are biobased, biodegradable polymers that can be produced efficiently by mixed microbial cultures (MMCs) at low cost. Substrate preferences have been found to vary depending on the microbial composition in the MMCs. In this study, the competition between the uptake of different substrates has been related for the first time to the abundance of certain microbial communities. With a higher abundance of Plasticicumulans enriched in the culture, the inhibitory effect of butyrate and valerate on the uptake of acetate and propionate increased and the hydroxybutyrate:hydroxyvalerate (HB:HV) ratio in the final PHA polymer approached the theoretical value calculated from the volatile fatty acid (VFA) composition. This finding can help understanding of the metabolism of PHA accumulating microorganisms and thus predict better the VFA consumption and PHA composition. [ABSTRACT FROM AUTHOR]