Isolation of phthalates degrading bacteria from activated sludge in petrochemical plant

BACKGROUND AND OBJECTIVESPhthalates are synthetic compounds widely used as plasticizers in various industries. Microorganisms, particularly bacteria, have demonstrated the ability to metabolize the hazardous phthalates. Activated sludge; a mixture of microorganisms commonly used in wastewater treatment plants, has been found to harbor diverse microbial communities with the capability to degrade a wide range of pollutants. The aims of this study were isolation and characterization of phthalate degrading bacteria from activated sludge in petrochemical plant.MATERIALS AND METHODSActivated sludge samples were collected from a wastewater treatment plant. About ۷ mL of the collect samples was inoculated into ۱۰۰ mL enrichment medium contains mineral salt medium (MSM) supplemented with ۰.۵ g L-۱ carbon of each dimethyl phthalate (DMP) or dibutyl phthalate (DBP) as sole carbon and energy source. The flasks were incubated on an orbital shaker at ۳۰ °C, ۱۲۰ rpm, pH ۷±۰.۲ during ۲-۷ days. The bacterial degradation activity was determined using a spectrophotometer at ۶۰۰ nm. The enriched cultures were plated out on selective agar to isolate individual phthalate degrading bacteria. The isolates were further characterized based on morphological, biochemical, and molecular techniques.RESULTS AND DISCUSSIONAmong ۱۱ isolates, two Gram negative bacteria named MAF۱ and MAF۱۱ were degraded both phthalates as a sole carbon and energy source. The results showed that degradation of DMP and DBP by MAF۱ and MAF۱۱ were initiated after ۱۲ hours then reached to a maximum after ۴۸ and ۱۲۰ hours incubation, respectively. In addition, the optical density assay in growth cultures contains DMP and DBP for both isolates were increased from ۰.۰۲۶ to ۰.۲۷۶ and ۰.۲۷ to ۰.۴۷۳, respectively.CONCLUSIONThe results demonstrated two bacteria isolated from activated sludge were able to degrade phthalates. These results revealed that both isolates are suitable for degradation of phthalates in industrial wastewater and contaminated sites.

کلیدواژه ها:

Phthalates ، degrading bacteria ، activated sludge