Enhancement of waste engine oil biodegradation by optimization of media using factorial design study

Biodegradation of spilled or dumped waste engine oil is a challenging task due to their toxicity and persistency in the environment. Waste engine oil biodegradation can be improved by optimizing media constituents that may stimulate the microbial degradation phenomenon and contribute to the progress of oil spill bioremediation process. In the present study, the effect of different nutrients, such as, carbon, nitrogen and inorganic ion source, added externally to Bushnell-Haas (BH) medium were investigated for waste engine oil biodegradation using a novel hydrocarbon degrading bacterium, Ochrobactrum pseudintermedium Cl. The bacterial strain was isolated in our laboratory from oil contaminated soil and identified by 16S rRNA gene sequencing. The results showed that the most significant variables influencing waste engine oil biodegradation were glucose, yeast extract and FeCl sub(3). A full factorial central composite design was applied for experimental work and analysis of the data. Moreover, these three factors interacted with each other and combined to produce positive effects on waste engine oil degradation. The experimental data also allowed the development of an empirical model (P < 0.00672) describing the inter-relationship between independent and dependent variables. By solving the regression equation, the optimal values of the variables were determined as (g/L): glucose 22.028, yeast extract 1.949 and FeCl sub(3) 0.225. The BH medium with the above constituents resulted in significant enhancement of waste engine oil percent degradation from 51.24 to 71.52% within 7 d.