Biodegradation of used engine oil by novel strains of Ochrobactrum anthropi HM-1 and Citrobacter freundii HM-2 isolated from oil-contaminated soil.

Haytham M M Ibrahim

doi:10.1007/s13205-016-0540-5

Abstract

Used engine oil (UEO) constitutes a serious environmental problem due to the difficulty of disposal off or reuse. Ten bacterial strains with biodegradation potential were isolated from UEO-contaminated soil sample using enrichment technique. Two strains which exhibited the highest degradation %, 51 ± 1.2 and 48 ± 1.5, respectively, were selected. Based on the morphological, biochemical characteristics and 16S rRNA sequence analysis, they were identified as Ochrobactrum anthropi HM-1 (accession no: KR360745) and Citrobacter freundii HM-2 (accession no: KR360746). The different conditions which may influence their biodegradation activity, including UEO concentration (1–6 %, v/v), inoculum size (0.5–4 %, v/v), initial pH (6–8), incubation temperature (25–45 °C), and rotation speed (0–200 rpm), were evaluated. The optimum conditions were found to be 2 % UEO, 2 % inoculum size, pH 7.5, incubation temperature 37 °C, and 150 rpm. Under the optimized conditions, strains HM-1, HM-2, and their mixture efficiently degraded UEO, they achieved 65 ± 2.2, 58 ± 2.1, and 80 ± 1.9 %, respectively, after 21 days of incubation. Biodegradation of UEO was confirmed by employing gas chromatography analysis. Gamma radiation (1.5 kGy) enhanced the degradation efficiency of irradiated bacterial mixture (95 ± 2.1 %) as compared to non-irradiated (79 ± 1.6 %). Therefore, strains HM-1 and HM-2 can be employed to develop a cost-effective method for bioremediation of used engine-oil-polluted soil.

Highlights

Pollution due to petroleum hydrocarbons and its derivatives, including diesel fuel, gasoline, heavy oil, motor oil, fuel residues, and mineral oil, has an increasing influence on the environmental reconquest (Su et al 2011)
Microbial consortiums have been usually suggested for complete biodegradation of petroleum pollutants (Farahat and El-Gendy 2008), since the constituents of hydrocarbon mixtures differ in their solubility, volatility, and susceptibility to biodegradation, and in contrast, the required sets of enzymes cannot be present in a single microbial strain
The spectrophotometric analysis of used engine oil demonstrated the presence of several heavy metals, including the following in: lead (2.5), nickel (23.4), iron (14), manganese (0.35), copper (0.18), and zinc (55.7)

Summary

Introduction

Pollution due to petroleum hydrocarbons and its derivatives, including diesel fuel, gasoline, heavy oil, motor oil, fuel residues, and mineral oil, has an increasing influence on the environmental reconquest (Su et al 2011) They have been recognized as one of the most hazardous wastes (Udeani et al 2009). Su et al (2011) demonstrated the motor-oil-degrading potential of an indigenous Pseudomonas aeruginosa SU-1 bacterial strain. This bacterium was found to have the ability to degrade motor oil efficiently upon growing in a medium containing such pollutant as the sole carbon source. Salam (2016) in his study established the extensive degradation ability of two Pseudomonas aeruginosa strains RM1 and SK1 on waste engine oil He reported the potentials of these strains in the degradation of aromatic, aliphatic, and branched alkane components of waste engine oils. In an attempt to enhance the biodegradation efficiency of these strains, the effect of gamma radiation was evaluated

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