Biodesulfurization: a model system for microbial physiology research.

Biological desulfurization (biodesulfurization) of dibenzothiophene (DBT) by the 4S pathway is a model system for an enviromentally benign way to lower the sulfur content of petroleum. Despite a large amount of effort the efficiency of the 4S pathway is still too low for a commercial oil biodesulfurization process, but the 4S pathway could potentially be used now for commercial processes to produce surfactants, antibiotics, polythioesters and other chemicals and for the detoxification of some chemical warfare agents. Proteins containing disulfide bonds are resistant to temperature, pH, and solvents, but the production of disulfide-rich proteins in microbial hosts is challenging. The study of the 4S pathway can provide insights as to how to maximize the production of disulfide-rich proteins. Engineering of the operon encoding the 4S pathway to contain a greater content of methionine and cysteine may be able to link use of DBT as a sole sulfur source to increasing 4S pathway activity by increasing the nutritional demand for sulfur. This strategy could result in the development of biocatalysts suitable for use in an oil biodesulfurization process, but the study of the 4S pathway can also lead to a better understanding of microbial physiology to optimize activity of a mult-step co-factor-requiring pathway, as well as the production of highly stable industrially relevant enzymes for numerous applications.