Biodesulfurization of crude oil: a mini review

The worldwide focus on having environmental friendly fuels has made refineries to increase the quality of the fuels. One of the major problems that refineries are facing is eliminating sulfur from crude oil. Global society is moving towards zero-sulfur fuel and one of the most common techniques for removing sulfur from oil is hydrodesulfurization (HDS), but this is a high-cost process and operates in hazardous operational conditions (high temperature and pressure). As a result, the oil agencies are constantly trying to find a more cost-effective and safe process to eliminate sulfur. One of the approaches is Biodesulfurization (BDS). BDS is a low-cost and environmentally friendly process that operates based on the potential of desulfurizing bacteria to remove sulfur from sulfur-containing compounds of crude fuels that are tenacious to the chemical treatments like dibenzothiophene (DBT). BDS operates at ambient temperature and pressure with high selectivity. So it has lower energy costs, low emission and no generation of undesirable side-products.There are different pathways in which bacteria degrade DBT and its derivatives and the most common one is the 4S pathway. In this pathway, sulfur is removed selectively whereas the carbon skeleton remains intact. Various factors affect the efficiency of BDS process such as media type and growth conditions, bioreactor design, the effect of absorption and immobilization, and presence of inhibitors, surfactants, and supplementary compounds. The main benefit of immobilization of enzymes and whole cells is repeated or continuous use of biocatalyst A large number of recombinant bacteria have been engineered to overcome the main difficulties of the BDS process such as expression of the dsz operon, the activity of the Dsz enzymes, inhibitory effects on the Dsz pathway, tolerance to organic solvents and metals, and other host-specific limitations. Applying new tools that modern biotechnology has provided for us such as genome sequencing, high throughput omic techniques, and synthetic biology approaches can be helpful to design optimized metabolic pathways and bacterial hosts. However, in order to industrialize BDS process, all the information and advances that are gained from the genetic engineering are needed to be applied to the process engineering. So parameters such as mass transfer rate, separation of the biocatalyst, kinetic modeling, scale-up of biphasic systems must be studied more

Keywords:

Biodesulfurization , Crude oil , Dibenzothiophene , Sulfur