Kinetic analyses of desulfurization of dibenzothiophene by Rhodococcus erythropolis in batch and fed-batch cultures

The DbtS(+) phenotype (which confers the ability to oxidize selectively the sulfur atom of dibenzothiophene [DBT] or dibenzothiophene sulfone [DBTO2]) of Rhodococcus erythropolis N1-36 was quantitatively characterized in batch and fed-batch cultures, In flask cultures, production of the desulfurization product, monohydroxybiphenyl (OH-BP), was maximal at pH 6.0, while specific productivity. (OH-BP cell(-1)) was maximal at pH 5.5, Quantitative measurements in fermenters (in both batch acid fed-batch modes) demonstrated that DBTO2 as the sole sulfur source yielded a greater amount of product than did DBT. Specifically, 100 mu M DBT maximally yielded approximate to 40 mu M OH-BP, while 100 mu M DBTO2 yielded approximate to 60 mu M OH-BP. Neither maintaining the pH at 6.0 nor adding an additional carbon source increased the yield of OH-BP. The presence of SO42- in growth media repressed expression of desulfurization activity, but SO42- added to suspensions of cells grown in DBT or DBTO2 did not inhibit desulfurization activity.