Screening for crude oil degrading bacteria in liquid organic waste (effluent samples)

The screening for crude oil degrading bacteria in some liquid organic wastes (cassava mill effluents,rubber effluents and oil palm mill effluents) was carried out. hydrocarbon utilising bacteria were isolated on mineral salt agar using vapour phase technique. the samples yielded 20 bacterial isolates from 13 different genera. cassava mill effluent and rubber effluent had the highest number (7),while oil palm effluent had the least number (6) of bacterial isolates. the isolates that had the highest occurrence (occurring in all samples) were pseudomonas aeruginosa and escherichia coli. of these 13 genera 9 were gram negative,while only 4 were gram positive. the total heterotrophic bacterial (thb) count and total hydrocarbon utilisers (thu) from all the effluent samples ranged from 3.0 × 104 to 6.0 × 107cfu/ml and 2.3 × 102 to 4.2 × 103cfu/ml,respectively. the counts of hydrocarbon utilisers were obviously lower than the heterotrophic counts,although the differences in counts were found to be statistically non-significant (p > 0.05). rubber effluents and oil palm mill effluents had the highest number of hydrocarbon utilisers with three isolates each. the active hydrocarbon utilisers encountered in this study included serratia marscescens,bacillus cereus,p. aeruginosa,enterobacter aerogenes and bacillus subtilis. presence of nutrients and crude oil degrading bacteria in these effluents suggests that these effluents can be used to enhance bioremediation through their use as biostimulation and bioaugmentation agents.