Low biomass output is a crucial reason for low polyhydroxyalkanoate (PHA) production in mixed microbial cultures (MMCs) PHA process. In this research, an extended cultivation strategy was proposed to rapidly expand the biomass yield of PHA accumulating MMCs and conserve the PHA accumulating ability simultaneously. High PHA content of the cultivated MMCs of 71.4% and 66.7% (higher than 62.1% of the seed biomass) in batch assays and biomass magnification of 43 and 52 were obtained after 10 days of extended cultivation with and without sludge discharge, respectively. By embedding the extended cultivation process into the production process, a highly competitive PHA production performance in terms of overall PHA storage yield (0.49 g COD PHA/g COD VFA) and volumetric productivity (1.21 g PHA/L/d with final cell density of 17.22 g/L) was achieved. The proposed PHA production process based on the extended cultivation can be a promising choice in industrial scale practice. (C) 2017 Elsevier Ltd. All rights reserved.