Desulfurization of alkylated forms of both dibenzothiophene and benzothiophene by a single bacterial strain

Thirty-five bacterial strains capable of converting dibenzothiophene into 2 -hydroxybiphenyl were isolated. Among them Rhodococcus erythropolis KA2-5-1 was chosen for further characterization because of its ability to retain h igh desulfurization activity stably. PCR cloning and DNA sequencing of a KA 2-5-1 genomic DNA fragment showed that it was practically identical with ds zABC genes from Rhodococcus sp. IGTS8, a representative carbon-sulfur-bond- targeted dibenzothiophene-degrading bacterium. KA2-5-1 desulfurized a varie ty of alkyl dibenzothiophenes through the specific cleavage of their C-S bo nds. In addition, unexpectedly, KA2-5-1 also attacked alkyl benzothiophenes in a C-S-bond-targeted fashion. The purified monooxygenase, encoded by dsz C of KA2-5-1, converted benzothiophene and dibenzothiophene into benzothiop hene sulfone and dibenzothiophene sulfone, respectively, with the aid of an NADH-dependent oxidoreductase. This result raises the possibility that the same enzymatic step may be involved in desulfurization of alkylated forms of both dibenzothiophene and benzothiophene: in KA2-5-1 cells, (C) 2000 Fed eration of European Microbiological Societies. Published bq; Elsevier Scien ce B.V. All rights reserved.