Isolation of a unique benzothiophene-desulphurizing bacterium, Gordona sp. strain 213E (NCIMB 40816), and characterization of the desulphurization pathway

Abstract

Gordona sp. strain 213E (NCIMB 40816) grew in pure culture in a mineral salts medium containing fructose as a source of carbon and energy, and benzothiophene (BTH) as the sole source of sulphur. During growth a phenolic compound accumulated, as indicated by the production of a blue colour on addition of Gibb's reagent. Therefore this pathway is analogous to the dibenzothiophene (DBT) desulphurization pathway of Rhodococcus sp. strain IGTS8, in which 2-hydroxybiphenyl accumulates during growth with DBT as the sole sulphur source. Ethyl acetate extraction of the culture medium yielded the metabolites benzothiophene S-oxide (BTHO), benzothiophene S,S-dioxide (BTHO2), benzo[c][1,2]oxathiin 6-oxide (BcOTO), 2-(2'-hydroxyphenyl)ethan 1-al (HPEal) and benzofuran (BFU). The deduced pathway for BTH desulphurization is BTH ? BTHO ? BTHO2 ? HPESi- ? HPEal. HPESi- is (Z)-2-(2'-hydroxyphenyl)ethen 1-sulphinate, the stable aqueous-solution form of BcOTO. It was concluded that HPEal was the Gibb's-reagent-reactive phenolic compound which accumulated in the culture medium of strain 213E during growth, and that the presence of BFU was due to partial condensation of HPEal during the ethyl acetate extraction procedure. Gordona sp. strain 213E was unable to grow in a mineral salts medium containing fructose as a source of carbon and energy and DBT as the sole sulphur source. BTH-desulphurization-active cells (grown using BTH as sole sulphur source) were unable to desulphurize DBT. Likewise Rhodococcus sp. strain IGTS8 was unable to grow using BTH as the sole sulphur source, and DBT-desulphurization-active cells of strain IGTS8 (grown using DBT as sole sulphur source) were unable to desulphurize BTH. This absence of cross-reactivity is discussed in terms of fundamental differences in the chemistry of the DBT- and BTH-desulphurization reactions.

Microbial transformation of benzothiophenes, with carbazole as the auxiliary substrate, by Sphingomonas sp. strain XLDN2-5

“…However, no bacterial strain has been found that is able to grow on benzothiophenes as the sole carbon source, and all reported biotransformations of benzothiophenes are based on cometabolism. Attacks on the thiophene ring of benzothiophenes lead to the formation of sulfoxides and sulfones, or to ring opening and the formation of 2-mercaptomandelaldehyde and 2-mercaptophenylglyoxalate (Saftić et al, 1992;Eaton & Nitterauer, 1994;Gilbert et al, 1998). Interestingly, it has been reported that BTO is trapped as a Diels-Alder-type disulfoxide cycloadduct, which yields (Kropp et al, 1994b).…”

“…Six metabolites of BT were detected by GC-MS: BTO 2 and 2-mercaptobenzoic acid were identified by comparison of their retention times and mass spectra with those of authentic compounds; 2-hydroxybenzothiophene, 3-hydroxybenzothiophene, benzothiophene-2,3-dione and BTO were identified by comparison of their mass spectra with published data (Saftić et al, 1992;Eaton & Nitterauer, 1994;Kropp et al, 1994b;Gilbert et al, 1998). These results indicate that strain XLDN2-5 is able to catalyse lateral dioxygenation and S oxidation on the thiophene ring of BT.…”

Aerobic Degradation of Petroleum Components by Microbial Consortia

“…However, no bacterial strain has been found to grow on benzothiophenes as the sole carbon source, and all reported biotransformations of benzothiophenes are based on cometabolism. Attacks on the thiophene ring of benzothiophenes lead to the formation of sulfoxides and sulfones, or to ring opening and the formation of 2-mercaptomandelaldehyde and 2-mercaptophenylglyoxalate [158][159][160]. Catabolism of dibenzothiophene is catalyzed by distinct enzymes in two pathways (Scheme 7).…”

Genotypic Characterization of Sulfur-Oxidative Desulfurizing Bacterial Strains Isolated from Mexican Refineries

“…The following strains were used for comparison: R. erythropolis IGTS8 (ATCC 53968) and R. erythropolis X309 (ATCC 55309). A minimal salt medium (MSM) was used for the isolation and cultivation of DBTdesulfurizing strains [18]. DBT and 4,6-dimethylDBT (4,6-DMDBT) were dissolved in hexane (50 mM) and added to the sterilized MSM.…”