Bioremediation of Petroleum Hydrocarbon Contaminated Soil Using Bacillus subtilis Strain – Process Optimization by Box Behnken Design

Abstract

Present study investigated bioremediation potential of Bacillus subtilis, a bacterial strain, in remediation of total petroleum hydrocarbons from oil contaminated soil. The study integrates the utilization of Bacillus subtilis for bioremediation of petroleum-contaminated soil with optimization using Box-Behnken experimental design. The process parameters were optimized using the Box-Behnken design, and the results were statistically interpreted using response surface methodology. Fifteen experimental runs were conducted with varying levels of pH (4.0 to 8.0), moisture content (40–70%), and salinity (0 g/L to 50 g/L). Lab - scale investigations were conducted utilizing PVC experiment vessel. Maximum hydrocarbon removal observed within 45 days was 83% under optimal conditions of pH 6, moisture content of 55%, and salinity of 25 g/L. A linear-quadratic regression model is used to fit the data for the process of Bioremediation, specifically for the removal of petroleum hydrocarbon from soil that has been contaminated. An analysis of variance (ANOVA) is conducted, and the adequacy of the model is evaluated. According to the model, the presence of moisture content and salinity has a beneficial impact, while the linear independent variables have an adverse impact. © The Author(s), under exclusive licence to Shiraz University 2025.