Optimization and modeling of used engine oil hydrocarbons degradation by Ochrobacterium intermedium LMG 3301 using response surface methodology

The pollution caused by the disposal of used engine oil (UEO) is a prevalent issue that results in soil contamination on a large scale. In this study, the UEO degrader of Ochrobacterium intermedium LMG 3301 strain was tested and modelled for its metabolic activities in enriched minimal salt medium (EMSM) supplemented with UEO to degrade n-alkane HC-Cpds in UEO. The RSM-DOE was applied to investigate the impact and optimization of three key variables (pH, temperature, and UEO concentration). The data analysis showed that the factor influencing O. intermedium growth was pH > temperature. Overall bacterial counts (TC) were positively impacted by the interaction of these variables (temperature and pH). The results of central composite design (CCD) data analysis demonstrated that the degradation of UEO by O. intermedium was more sensitive to pH than temperature and UEO concentration. The combined effects of those variables with the dominance of pH caused a positive effect on the TPH degradation rate of UEO. The data fit the model (P < 0.001) with a calculated R 2 of 0.9967. Applying the software optimization, the optimal values of EMSM conditions were determined as pH = 7.5, temperature = 35 °C, and UEO concentration = 5 g/L (0.675 % (v/v)), at 150 rpm. Using the medium obtained, the 14,800 μg/mL (93 %) UEO was degraded within 24 days in 100 mL of EMSM. At this optimal condition, the experimental UEO degradation value (91 % UEO) was in good close agreement with the value predicted (14959 μg/mL, or 94 %) by the software optimization. These studies with O. intermedium may be of great significance in formulating augmented bioremedy studies to remove UEO from the environment.