Growth study on chrysene degraders isolated from polycyclic aromatic hydrocarbon polluted soils in Nigeria

Acinetobacter anitratus, Alcaligenes faecalis, Acinetobacter mallei and Micrococcus varians were isolated from polycyclic aromatic hydrocarbon polluted soils by enrichment culture using chrysene as sole carbon and energy source. Physiochemical evaluation revealed that these isolates grew well at a temperature range of 20-40 degrees C, pH 6.0-8.0 but less tolerable to various salt concentrations except Micrococcus varians which grew at 1.0 to 7.5% NaCl. These organisms utilized chrysene, anthracene, naphthalene, crude oil, kerosene, diesel and engine oil as sole carbon source. None could utilize benzene, hexane, xylene, phenol and toluene as carbon sources. Growth study of the isolates on 0.1% ( w/v) chrysene resulted in highest cell density of 8.8x10(7), 7.9x10(7), 6.3x10(6), 6.3x106 cfu/ml for A. anitratus, Alc. faecalis, A. mallei and M. varians, respectively. There was statistical significant difference ( P < 0.05) in the growth of these organisms on chrysene as sole carbon and energy source when compared with non-chrysene control. This study indicates the potential of these hitherto unreported tropical bacterial strains as chrysene degraders and their use in biodegradation processes involving petrochemical products.