Biodesulfurization of DBT by a hyperthermophilic archaeon Sulfolobus solfataricus P2

Abstract

Combustion of fossil fuels leads to the atmospheric emission of sulfur oxides that contribute to acid rain. Significant quantities of sulfur (up to 70%) in petroleum is found as recalcitrant heterocyclic organosulfurs [dibenzothiophene (DBT) and substituted DBTs]. Current sulfur removal processes involve hydrodesulfurization, which requires high temperatures and pressure for efficient catalysis. Biodesulfurization is an alternative method for oil and coal industry offering low costs and relatively easy operating conditions. The present study describes the usage of a hyperthermoacidophilic archaeon S. sulfotaricus P2 in the utilization of sulfur compounds from variety of organic and inorganic compounds at high temperatures, between 75 and 85◦C and low pH, 3.0. To establish optimal sulfur free conditions, carbon sources containing arabinose, ethanol, glucose, mannose and mannitol have been employed to find the most suitable sources. Growths on the sulfur sources such as DBT, dibenzothiophene sulfone, BT, 4,6- dimethyldibenzothiophene, sodium sulfite, potassium disulphite, and potassium persulphate were investigated. 0.3mm of all sulfur supplements except DBT led to increases in the growth rate from 1.35 to 2.0-fold. Further investigations revealed the maximum DBT tolerance as 0.1mm. It was found that 88.5% of DBT was consumed and maximum desulfurization rate was obtained as 1.23mol 2-HBP hour−1 gDCW−1 within 16.5 hours. Our results also revealed that DBT sulfone consumption is the rate limiting step in the overall DBT usage process for S. solfataricus. To the best of our knowledge,this is the first report showing the DBT desulfurization kinetics analysis of S. solfataricus.