on PHA have been performed with pure cultures or genetically modified organisms and using valuable industrial by-products as substrate. However, at the moment, the interest is moving to the application of microbial mixed cultures (MMCs), using waste streams as substrate characterized by their large organic matter content. In this latter case, PHA can be produced by MMCs selected by the exploitation of the ecological role of PHA as a microbial storage material [3], when dynamic operational conditions are applied to the system.