The extensive use of petroleum–based synthetic plastics is leading to various environmental problems such as ecological impact, and untreated plastic waste, particularly micro–plastic pollution. Bioplastics are, therefore, considered one of the prospective solutions to replace conventional plastics. PHAs (polyhydroxyalkanoates), one of the widely studied and applied bioplastics, is synthesized by microorganisms when their living conditions are unfavorable. Many species of microorganisms capable of synthesizing PHAs are found in different environments. In the study, we focus on isolating and screening bacteria capable of synthesizing PHAs from activated sludge of paper mill wastewater treatment system. The results have shown two types of bacteria that have the highest synthesizing productivity: Bacillus Megaterium BP5 and Alcaligenes Aquatilis BP6. Their highest yield of PHAs synthesis was reached at the time 48 hours of incubation, which their dry biomass of 41.19% and 49.11%, respectively.