Abstract Aims: The biodesulfurization activity of bacteria through the 4S pathway in aqueous-oil emulsions is affected by various operational factors. These factors also demonstrate interacting effects that influence the potential for field applications of biodesulfurization technology and can solely be deciphered through multi-variable experiments. In this study, the effects of the influential factors and their interactions on the desulfurizing activity of a newly identified desulfurizing bacterium, Rhodococcus sp, FUM94 were quantitatively investigated. The capacity improvement achieved through optimized values obtained in this study is significant due to its simple implementation to large scale processes. This is the most simple and the most cost-effective way to scale-up a biodesulfurization process. Methods and results: Using response surface methodology (RSM). Optimum values of the factors were identified with the objective of maximizing biodesulfurization activity. Results revealed that the desulfurization activity of the biocatalyst increased from 0.323±0.072 to 46.57±4.556 mmol 2-Hydroxybiphenyl (kg dry cell weight)-1h-1 at the optimized conditions of 6 h reaction time, 2 g.L-1 biocatalyst concentration, 0.54 mM (100 ppm) dibenzothiophene (DBT) concentration (sulfur source), and 25% oil phase fraction. Conclusions: Desirability analysis proved that the selected conditions are the most desirable combination of factors (desirability value=0.896) to achieve the highest biodesulfurization activity of the biocatalyst. Significance and impact of the study: A comparison between the biodesulfurization capacity achieved in this study and the capacities reported in similar studies published in the past two decades revealed that biodesulfurization under optimized operational conditions outperforms previously proposed techniques.

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