Insights into the Kinetics of the Microbial Degradation of Dibenzothiophene (DBT) by Acidithiobacillus ferrooxidans

Dibenzothiophene (DBT) is a major form of organo-sulfur compound chiefly found in coal. Acidithiobacillus ferrooxidans cells played the role of catalyst in degrading DBT to 2-hydroxy biphenyl (2HBP) through the formation of dibenzothiophene-sulfone and releasing the sulfur present in it. Experiments on the biodegradation of DBT by A. ferrooxidans bacterium using 9K medium with DBT at 3 g/L in a 500 mL shake flask scale achieved degradation of DBT up to 95% in 12 days. The A. ferrooxidans cells degrade DBT to 2-hydroxy biphenyl and release the sulfur atom in DBT through the formation of the intermediate dibenzothiophene-sulfone. The formation of 2HBP from microbial degradation of DBT followed the chemical control model of shrinking core reactions model in solid-liquid interactions. The kinetics of the DBT degradation by A. ferrooxidans followed first-order for a low initial concentration of DBT (3 g/L), and the kinetics were shifted to second-order with an increase in DBT concentration to 5 g/L.