Characterization of Truncated dsz Operon Responsible for Dibenzothiophene Biodesulfurization in Rhodococcus sp. FUM94.

Numerous desulfurizing bacteria from the Rhodococcus genus harbor conserved dsz genes responsible for the degradation of sulfur compounds through 4S pathway. This study describes a newly identified desulfurizing bacterium, Rhodococcus sp. FUM94, which unlike previously identified strains encodes a truncated dsz operon. DNA sequencing revealed a frameshift mutation in the dszA gene, which led to an alteration of 66 amino acids and deletion of other C-terminal 66 amino acids. The resulting DszA polypeptide was shorter than DszA in Rhodococcus sp. IGTS8 reference strain. Despite the truncation, desulfurizing activity of the operon was observed and attributed to the removal of an overlap of dszA and dszB genes, and lack of active site in the altered region. Desulfurization experiments resulted in specific production rate of 6.3 mmol 2-hydroxy biphenyl (kgDCW) h at 2 g l biocatalyst concentration and 68.8% biodesulfurization yield at 20 g l biocatalyst concentration, both at 271 μM dibenzothiophene concentration which is comparable to similar wild-type biocatalysts.