Objectives : In this research work, we investigated the biocatalytic potency of orange and watermelon garbage enzymes in the remediation of used motor oil-contaminated soils. The optimization of the biocatalytic remediation process was evaluated through D-optimal of response surface methodology (RSM) design of design expert. Methods : The optimization of the biocatalytic process was evaluated with D-optimal model of response surface methodology (RSM) design, where input variables in the system

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... ere garbage enzymes solutions of orange and watermelon peels (biocatalysts) and two different pollution levels. The two levels of pollution factor considered were 5 and 10 % (w/w) oil pollution levels and used as independent variables; while the response of the system was in oil and grease (O&G) removal as dependent variables that were monitored under 6-week remediation process. Results and Discussion : The result indicated that the model was highly significant and good predictors of the response fate of oil and grease (O&G) removal by the orange and watermelon garbage enzymes, as indicated by their coefficients of determination: R2 = 0.90627 and R2 = 0.88365 at p < 0.05, respectively. Therefore, it was observed from the numerical optimization carried out that 54.2 and 53.8 % O&G removal was achieved with orange garbage enzymes at 5 and 10 % pollution level respectively after six weeks. On the other hand, 54.7 and 55.2 % O&G removal was accomplished with the same pollution level respectively under the influence of watermelon garbage enzymes after six weeks of the remediation process. Conclusion : In response to what was achieved in this research work, the enzymes produced from the orange and watermelon garbage removed oil in terms of O&G from used motor oil-contaminated soils biocatalytically and hence could be applied in the remediation of oil contaminated soils.