The aim of this study was to set the operating mode in regards to nutrients, temperature and light to use as a strategy to enrich a microbiome rich in cyanobacteria in polyhidroxybutyrate (PHB)-producers in order to enhance the biopolymer production. Alternate growth and accumulation phases were conducted for 179 days in a 3 L photobioreactor. Although, presence of green microalgae potentially reduced PHB production, the microbiome produced up to 22 % dry cell weight (dcw) PHB. Results highlighted the important role of culture composition and suggested that this methodology could be applied to a robust microbiome rich in cyanobacteria to boost PHB production.