Biodegradation of Used Engine Oil by a Methylotrophic Bacterium, Methylobacterium Mesophilicum Isolated from Tropical Hydrocarbon-contaminated Soil

Abstract

A Gram-negative facultatively methylotrophic bacterium putatively identified as Methylobacterium mesophilicum strain RD1 displayed extensive degradative ability on used engine oil (SAE 40W) in liquid cultures. The rate of degradation of used engine oil (1274.85 mg L⁻¹) by the isolate, for the first 12 days and the last 9 days were 65 and 40 mg L⁻¹ d⁻¹, respectively. Gas chromatographic (GC) analyses of residual used engine oil revealed that 61.2% and 89.5% of the initial concentration of the used engine oil were degraded within 12 and 21 days. GC fingerprints of the used engine oil after 12 days of incubation 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 (96.8%) fractions were observed. In addition, less than 10% of Day 0 values of medium fraction ranges C₁₃, C₁₄, and C₁₆ were discernible after 21 days. This study has established the potential of Methylobacterium mesophilicum strain RD1 in degradation of aliphatic, aromatic, and branched alkane components of used engine oils.

Keywords:

• Biodegradation
• Methylobacterium mesophilicum
• Used engine oil
• pristane
• phytane