Optimization of Growth and Toluene Degradation by Free and Immobilized Bacillus Cereus ATHH39

Fatemeh Heydarnezhad

Mehran Hoodaji

Mahdi Shahriarinour

Arezoo Tahmourespour

Abstract

A toluene-degrading bacterium with high tolerance of toluene was isolated from oilcontaminated soils. DNA sequencing and homologous analysis identified it as Bacillus cereus sp. Toluene degradation was optimized in respect to pH, temperature and toluene concentration using response surface methodology with central composite design. At optimal pH (6.7), temperature (33◦ C) and toluene concentration (825 mg/L) predicted degradation was 65.5%. Carbon nanotubes were used to immobilize the Bacillus; immobilized cells degraded toluene by 87.5% tolerated a higher toluene levels and protected the bacteria against changes in temperature and pH. These results indicate that immobilized Bacillus cereus strain ATHH39 possesses
a good application potential in the treatment of toluene-containing soils.