Enrichment of PHA-producing bacteria under continuous substrate supply.

To enrich polyhydroxyalkanoate (PHA) producing microbial communities, generally, a feast-famine regime is applied. Here we investigated the impact of continuous substrate feeding on the enrichment of PHA-producing bacteria in two sequencing batch reactors (SBRs). In the first reactor, the substrate (acetate) was dosed continuously and Zoogloea sp. was enriched. The culture accumulated PHA upon exposure to excess carbon, but the PHA production rate and storage capacity (53 wt.%) were one-fifth of that observed for enrichment cultures in a standard, pulse-fed SBR dominated by the PHA producer Plasticicumulans acidivorans. In the second reactor, half the acetate was dosed at the beginning of the cycle and the other half continuously. Having a true feast phase, the enrichment of P. acidivorans was not impeded by the continuous supply of acetate and the culture accumulated 85 wt.% PHA. This shows that for the enrichment of bacteria with a superior PHA-producing capacity periodic substrate excess - a true feast phase - is essential, while periodic substrate absence - a true famine phase - is not.