Assessing the synergistic relationship of mycorrhiza and bacteria for the degradation of spent engine oil in maize grown soil

Abstract

Abstract Background Pollution by waste hydrocarbons on soil and water bodies is an endemic problem in African countries, particularly in Nigeria. This has caused untold hardship and increase in poverty level of the people, due to the pollution of water and land; which had direct impacts on the livelihood of people. Several species of bacteria that can degrade hydrocarbon had been isolated from the root of plants. The aim of this work was to determine the ability of rhizosphere bacteria to degrade spent engine oil (SPO) in the presence of arbuscular mycorrhiza fungus. Results The total aerobic count in the eight treatments ranged between 3.0 × 106 and 1.18 × 108 CFU/g. No significant difference was observed in the total aerobic count among the treatments except when compared with the control experiment (M−C−). Isolated bacteria from the polluted soil samples were identified by 16S rRNA sequencing as Bacillus cereus, Pseudomonas aeruginosa, Bacillus amyloliquefaciens, Lysinibacillus fusiformis, Bacillus enecimensis, and Paraclostridium benzoelyticum. Four of the bacteria were able to utilize spent engine oil effectively to different degrees. However, Lysinibacillus fusiformis biodegraded spent engine oil by 40%, Paraclostridium benzoelyticum by 30% and Bacillus enecimensis by 20% after 28 days of incubation. The infrared analysis result revealed that Lysinibacillus fusiformis (P6) reduced the strong and band of alcohol by 44%, carboxylic acid group by 22% and carbonyl group by 27%, respectively. This study revealed that spent engine oil at a minimum value of 50 mg/kg with arbuscular mycorrhiza fungus in the soil samples resulted in better growth for maize plant and higher total aerobic count. Conclusions It can thus be concluded that arbuscular mycorrhiza fungus positively impacts the ability of rhizosphere bacteria in the degradation of spent engine oil and the growth of maize plant on contaminated soil.