Wastewater of petrochemical industries contains high amounts of emulsified aliphatic or aromatic hydrocarbons that lead to the contamination of almost all environmental resources. The ability of Haloarcula sp. IRU1 isolated from Urmia lake, Iran for utilization of petrochemical wastewater and production of poly(3-hydroxybutyrate) (PHB) from it was evaluated and optimized by Taguchi experimental method. The optimium conditions for the maximum production of PHB were petrochemical wastewater 2% (as carbon source), tryptone 0.8% (as nitrogen source), KH2PO4 0.001% (as phosphorus source) and temperature 47 degrees C. In conclusion, Haloarcula sp. IRU1 can degrade petrochemical wastewater and produce PHB from it in different conditions. (C) 2011 Elsevier B.V. All rights reserved.