Biodesulfurization of Dibenzothiophene by a Newly Isolated Thermophilic Bacteria Strain

Microbiological analyses of soil chronically exposed to petroleum complex compounds of some oil springs in south of Iran resulted in isolation and purification of a new native thermophilic strain which is capable to desulfurize petroleum sulfur compounds by 4-S mechanism. Dibenzothiophene (DBT) was selected as a complex sulfur compound model and many experiments were done to identify the metabolic pathway. The results of these experiments show that DBT is ultimately converted to 2-hydroxybiphenyl (2-HBP) and sulfite. This is a special metabolic pathway in that there is no effect on the carbon skeleton of organic compounds and would be ideal for desulfurization to upgrade the petroleum products because it keeps the remaining hydrocarbon molecules fully active as energy sources without any loss of their thermal units. At the next step, some physical and chemical properties of main culture were optimized as follows: 6gr/lit glucose, 4gr/lit ammonium chloride, 0.15 mM DBT, pH= 7 and temperature= 45°C. During 6 days, growing cells of this microorganism can convert 87.5% of DBT in 250 ml flask. At last, kinetic analysis has been done and Michaelis-Menten equation qualified. Equation parameters Vmax and KM calculated and data led to 0.548 mM h−1 and 0.458 mM, respectively.