The recalcitrance and poor solubility of hydrocarbons have continually been merging challenges in bioremediation of polluted sites as such efforts have been directed into finding means to improve absorption of these compounds. The present study investigated the potential of
Acinetobacter anitratus
and
Acinetobacter mallei
to grow on and degrade varying concentration of chrysene and diesel oil respectively over a 7 day period. In addition, hydrocarbon emulsification, haemolytic activity and macromolecule secretion were also evaluated using the microbial extracellular culture media. Both isolates grew on the carbon sources in a concentration dependant manner. Residual chrysene obtained after degradation of 30, 50 and 100 mg/l respectively by
A. anitratus were 0.02 ± 0.01, 2.15 ± 0.4 and 18.5 ± 0.7 mg/l while with
A. mallei, they were 0.02 ± 0.03, 2.18 ± 0.6 and 29.5 ± 1.2 mg/l. Total hydrocarbon remaining after degradation of 3, 5, 15 and 30 % (v/v) diesel oil respectively using
A. anitratus were 0.0 %, 0.0 %, 17.5 ± 0.9 % and 43.9 ± 1.1% whereas with
A. mallei, they were 0.0 %, 2.1 ± 0.4%, 30.4 ± 0.5 % and 67.2 ± 1.4 % correspondingly. Extracellular fluid of both isolates from diesel oil growth media showed emulsification activities against kerosene, diesel oil, engine oil, hexadecane, dodecane and xylene at varying degree while no emulsification activity was observed when the isolates were grown on chrysene. Moreover,
A. anitratus and
A. mallei showed haemolytic activity when grown on diesel oil but not on chrysene. However, extracellular fluid from both chrysene and diesel oil growth media showed significant (P<0.05) difference in extracellular protein and carbohydrate concentration compared to non-carbon source growth media. Therefore, the significant (P<0.05) differences between both species of the
Acinetobacter in terms of cell densities, bioemulsification, haemolysis and extracellular composition suggest that microbial biotransformation of pollutant may be dependent on microbial specie used, pollutant degraded and genetic make-up of isolate which determine macromolecules that are expressed.
