Abstract

Two fluorene-degrading Gram-positive Bacillus strains, putatively identified as Bacillus subtilis BM1 and Bacillus amyloliquefaciens BR1 were isolated from hydrocarbon- and asphalt-contaminated soils in Lagos, Nigeria. The polluted soils have a relatively high total hydrocarbon content (16888.9 and 9923.1 mg/kg, respectively), very low concentrations of macronutrients and the total organic carbon was less than 4%. The two strains tolerated NaCl concentration of up to 7% while strain BR1 exhibited moderate growth at 10%. Shared resistance to ceftriazone and cotrimozaxole were exhibited by both strains while only strain BM1 was resistant to both amoxycilin and streptomycin. The rate of degradation of fluorene (50 mg/L) by the two isolates, after 30 days of incubation were 0.09 and 0.08 mg/L/h for strains BM1 and BR1, respectively. Gas chromatographic analyses of residual fluorene, revealed that 56.9 and 46.8% of 50 mg/L fluorene was degraded in 12 days by strains BM1 and BR1. However, after 21 days on incubation, 86 and 82% of 50 mg/L fluorene were degraded by strains BM1 and BR1, respectively. To the best of our knowledge, this is the first report highlighting flourene degradation potential of Bacillus strains isolated from tropical African environment.

Key words: Biodegradation, fluorene, hydrocarbon-contaminated soils, Bacillus spp.