African Journal of Biotechnology Vol. 5 (4), pp. 351-356, 16 February 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

Biodesulfurization of dibenzothiophene and its alkylated derivatives through the sulfur-specific pathway by the bacterium RIPI-S81

Ladan Rashidi^1*, Ghasemali Mohebali², Jafar Towfighi darian¹, Behnam Rasekh²

¹Chemical Engineering Department, Tarbiat Modarres University, Tehran, P.O.BOX. 14115- 4838, Iran.

²Department for microbiology, Research Institute of Petroleum Industry, Tehran, P.O.BOX. 18745- 4163, Iran.

*Correspondence author.  E-mail: ladan_rsh@myway.com; Fax number: 0098-021-8057007.

Abbreviations: Biodesulfurization or biocatalytic desulfuri-zation; C x –DBT,  Alkyl dibenzothiophene; DBT, Dibenzothio-phene; DBTO, Dibenzothiophene sulfoxide; DBTO2, Dibenzo-thiophene sulfone; DBTs, Dibenzothiophenes; DCW, Dry cell weight; 4,6-DMDBT, 4,6-Dimethyl dibenzo-thiophene; dsz , De-sulfurization; 2-HBP, 2- Hydroxy biphenyl; 2-HDMBP, 2-Hydroxy 3,3′-dimethyl biphenyl; HDS, Hydrodesul-furization; 2-HMBP, 2-Hydroxy 3- methyl biphenyl; 2′-HMBP, 2-Hydroxy 3′-methyl biphenyl; and 4-MDBT, 4-Methyl dibenzothiophene.

Accepted 23 June, 2005

RIPI-S81 is a new dibenzothiophene (DBT)-desulfurizing bacterium, which was isolated by Research Institute of Petroleum Industry in Iran. Resting cells and growing cells of RIPI-S81 was able to convert alkylated dibenzothiophenes (Cx-DBTs) to hydroxybiphenyls such that they were almost stoichiometrically accumulated as the dead-end metabolites of Cx-DBTs desulfurization in the medium containing minimal salt (MSM) and nutrients. RIPI-S81 could desulfurize up to 80% of 4,6-dimethyldibenzothiophene and 50% of methyldibenzothiophene in the MSM containing 40 mg/l of a sulfur source. The molecular structures of metabolites and the reduction of Cx-DBTs were analyzed using GC-MS and HPLC. The position of alkyl substitutes and the sulfur substrate affected desulfurization rates.

Key words: Biodesulfurization, dibenzothiophene, 4, 6-dimethyldibenzothiophene, 4-methyldibenzothiophene.