Biodegradation of aniline by Enterobacter ludwigii KH-5 isolated from the soil around Shiraz refinery, Iran

Aniline is a harmful substance that pollutes the environment and seriously endangers human health. In the present study five different bacteria were enriched and isolated from the soil around Shiraz refinery (Iran) as aniline degrading bacteria. They were identified as Enterobacter ludwigii KH-5, Raoultella planticola KH-A2, Alcaligenes faecalis KH-A3, Serratia marcescens KH-A4 and Microbacterium barkeri KH-A1 based on 16S rDNA gene sequencing. The highest aniline degradation rate (96%) was observed by E. ludwigii KH-A5. This strain with the greatest amount of minimum inhibitory concentration (MIC) was the most aniline resistant bacterium. The optimum pH and temperature that supported biodegradation of aniline by strain KH-A5 were 7.0 and 28-35 °C, respectively. The maximum growth and biodegradation of aniline by KH-A5 were observed at the initial aniline concentration of 100 mg l^-1. The strain could growth on aniline up to concentration of 700 mg l^-1 with the degradation rate of 11%. Further studies demonstrated that the addition of 0.5 g l^-1 glucose or potassium nitrate as a second carbon or nitrogen source could slightly enhance the biodegradation efficiency from 96.0% to 99.0%. However, even more addition of glucose or potassium nitrate could not further enhance the biodegradation process but delayed the biodegradation of aniline by the strain KH-A5. It could be concluded that these new strains, particularly E. ludwigii KH-A5, have a potential use for bioremediation of the site contaminated with aniline.