Isolation and identification of PHA producing bacteria from oil contaminanted soils in Masjed Soleiman and optimization of producing conditions

Introduction: Polyhydroxyalkanoate (PHA) is counted biodegradable polymer, produced by bacteria, which is employed instead of petrochemical plastics, to reduce environment pollution. The purpose of this study is the isolation and identification of the PHA producing bacteria in Masjed-Soleiman oil fields, determination of PHA produced by the bacteria, determine the optimal conditions of temperature, pH, concentration and type of carbon and nitrogen sources on the level of PHA synthesis and the use of waste oil as a cheap substrate of carbon for the synthesis of PHA by isolated bacteria. Materials and methods: At first 9 samples of soil contaminated with crude oil, from 9 points at 4 well sites in Masjed-Soleiman oil field were taken. The initial screening was done by MSM at the temperature of 28 °C. Isolates from the view point of producing PHA, were confirmed, by using Sudan black stain and were identified by using phenotypical tests and 16S rRNA sequence determination. Also, optimization of temperature, pH, carbon and nitrogen sources were made for bacteria growth. Results: In this study eleven isolates were identified as PHA producers and among them the highest range belongs to MIS-1 strain by the range of 58.522 percent of the cellular dry waight, wich produces the maximum PHA. This isolate is recognized as the species of pseudomonas aeroginosa according to the phenotypic tests and sequence analysis of 16S rRNA with 95 % similarity. In addition, the results of optimization tests showed that, the isolates in the temperature of 37 °C, pH7, glucose as the source of carbon and ammonium sulphate as the source of nitrogen and finally, concentration of 10 g/lit of the carbon source and 0.5 g/lit of nitrogen source, the highest range of PHA was synthesized. Discussion and conclusion: The results of this research show that the soil polluted with crude oil of Masjed- Soleiman oil field, in long term and also due to high rate of carbon, provides a suitable environment for screening of beneficial bacteria such as PHA producing bacteria