Metabolism of waste engine oil by Pseudomonas species

Abstract

Two bacterial strains phylogenetically identified as Pseudomonas aeruginosa strains RM1 and SK1 displayed extensive degradation ability on waste engine oil (SAE 40W) in batch cultures. Spectrophotometric analysis revealed the presence of various heavy metals such as lead, chromium and nickel in the waste engine oil. The rate of degradation of waste engine oil by the isolates, for the first 12 days and the last 9 days were 66.3, 31.6 mg l^-1 day^-1 and 69.6, 40.0 mg l^-1 day^-1 for strains RM1 and SK1, respectively. Gas chromatographic (GC) analyses of residual waste engine oil, revealed that 66.58, 89.06 % and 63.40, 90.75 % of the initial concentration of the waste engine oil were degraded by strains RM1 and SK1 within 12 and 21 days. GC fingerprints of the waste engine oil after 12 days of incubation of strains RM1 and SK1 showed total disappearance of C₁₅, C₂₃, C₂₄, C₂₅ and C₂₆ hydrocarbon fractions as well as drastic reductions of C₁₃, C₁₄, C₁₆ and PAHs fractions such as C₁₉-anthracene and C₂₂-pyrene. At the end of 21 days incubation, total disappearance of C₁₇-pristane, C₂₂-pyrene, one of the C₁₉-anthracene and significant reduction of C₁₈-phytane (97.2 %, strain RM1; 95.1 %, strain SK1) fractions were observed. In addition, <10 % of Day 0 values of medium fraction ranges C₁₃, and C₁₆ were discernible after 21 days. This study has established the potentials of P. aeruginosa strains RM1 and SK1 in the degradation of aliphatic, aromatic and branched alkane components of waste engine oils.

Keywords: Biodegradation; Phytane; Pristane; Pseudomonas aeruginosa; Waste engine oil.

Fig. 1

Growth dynamics of Pseudomonas species in CFMM amended with 2 % (1 ml) spent engine oil. Spent engine oil was not degraded in flasks inoculate with heat-killed cells. Data points represent the mean of three replicate flasks. In the case of population counts, error bars represent standard deviation. Residual spent engine oil was determined with reference to spent engine oil recovered from heat-killed controls

Fig. 2

Gas chromatographic traces of n-hexane extract of recovered spent SAE 40 engine oil from culture fluids of Pseudomonas aeruginosa strain RM1 at Day 0 (a), Day 12 (b) and Day 21 (c) of incubation at room temperature. The oil components were separated on 30 m long HP-5 column (internal diameter 0.25 mm; film thickness 0.25 µm) in a Hewlett Packard 5890 Series II gas chromatograph equipped with flame ionization detector (FID)

Fig. 3

Gas chromatographic traces of n-hexane extract of recovered spent SAE 40 engine oil from culture fluids of Pseudomonas aeruginosa strain SK1 at Day 0 (a), Day 12 (b) and Day 21 (c) of incubation at room temperature. The oil components were separated on 30 m long HP-5 column (internal diameter 0.25 mm; film thickness 0.25 µm) in a Hewlett Packard 5890 Series II gas chromatograph equipped with flame ionization detector (FID)