Biodesulfurization of Crude Oil: Mechanisms and Emerging Approaches for Process Enhancement

The presence of sulfur compounds, ranging from 0.05% in sweet oil to 10% in very sour oil, greatly reduces the economic value and quality of crude oil. These cause operational problems in refining, such as catalyst poisoning, equipment corrosion, and the release of sulfur oxides (SOx) upon burning. Conventional hydrodesulfurization is fine for simple sulfur-containing compounds, but recalcitrant aromatic heterocycles such as dibenzothiophene (DBT) present a challenge. High temperatures and pressures are required, which drive costs and catalyst issues. Other methods, such as adsorption, extraction, and oxidation, suffer from selectivity and cost issues. In this context, biodesulfurization (BDS) is a greener alternative to the above, without the use of metal catalysts. It uses microbial mechanisms that can be anaerobic or aerobic. Anaerobic pathways convert sulfur compounds to H2S at low rates, whereas aerobic pathways, including the Van-Ferden and Kodama pathways and the 4S pathway, have variable efficiency. In particular, the 4S pathway of Rhodococcus erythropolis effectively transforms DBT into 2-hydroxybiphenyl, while retaining calorific value. The review takes an innovative approach to exploring synergistic strategies to improve biocatalyst performance through genetic engineering, gene cluster optimization, and the development of solvent-resistant strains. Process intensification is the integration of biology and nanotechnology. Magnetic nanoparticles and deep eutectic solvents improve mass transfer. AI and machine learning optimize bioreactor conditions and predict metabolism.