Bacillus cereus and Pseudomonas aeruginosa isolated from Kaduna refining and petrochemical company (KRPC) were subjected to ultra-violet (UV)-irradiation for 30 min followed by nitrous acid treatment and re-irradiated with UV light for 30 min using standard methods and their petroleum degradation abilities were compared with parent strains. Prior to modification, B. cereus and P.aeruginosa grew on minimal basal medium containing 1.5 and 1% crude oil, respectively, initially but on re-inoculation, both organisms grew on minimal basal medium containing 5% crude oil. 99.83 (0.17% survival) and 96.91% (3.08% survival) death were recorded on UV-irradiation for 30 min; 38.24 (61.76% survival) and 82.02% (10.98% survival) death were recorded after nitrous acid treatment and 29.01 (70.99% survival) and 95.76% (4.24% survival) death were observed on re-irradiation with UV light for 30 min for B. cereus and P. aeruginosa, respectively. Petroleum product degradation increased from98.92% for parent B. cereus to 99.70% for UV-irradiated nitrous acid treated B. cereus, and from 91.34% for parent P. aeruginosa to 98.09% for UV-irradiated nitrous acid treated P. aeruginosa. However, itdecreased from 98.92 to 97.87% and increased from 91.34 to 97.87% for parents and second stage mutants re-irradiated with UV light of B. cereus and P. aeruginosa, respectively. Higher potential were observed for second stage mutant of B. cereus than P. aeruginosa. Thus, the modification of the organisms with UV-irradiation for 30 min followed by nitrous acid treatment resulted in their increased petroleum product degradation ability and could therefore be used for bioremediation of environmentspolluted with petroleum products of 1 - 5% (v/v)
