关键词: biodegradation;biodesulfurization;dibenzothiophene;bacteria strain

Abstract: Five bacterial strains, which are able to grow and to disintegrate dibenzothiophene (DBT)
and dibenzothiophene sulfone (DBTO2) in fossil fuels, are isolated. Analysis of products of
DBT metabolized by these strains shows that different bacteria strains oxidize DBT by
different pathways. The isolated strains R-6, R-16, R-9 and R-8 can metabolize DBT to DBTO2
and 2-hydroxybiphenyl (HBP), which are identified as Bacillus brevis, Bacillus sphaericus,
Nocardia globerula and Pseudomonas delafieldii respectively. Another strain R-12 identified
as Pseudomonas sp. can degrade DBT completely but it cannot produce DBTO2 and HBP. The
optimum temperature and initial pH for desulfurization by R-8 are 32℃ and 7.02
respectively and pH of the broth decreases during biodegradation. The growth of strain R-8
with different sulfur-sources indicates that this strain in DBT medium has an induction
period of 3 days, which is longer than those with dimethylsulfoxide and MgSO4 media, but
the growth rate of the bacterial strain in DBT is higher after the induction. Higher growth
and desulfurization rates are observed in the DBT-hexadecane system than in both DBT-
ethanol and DBT-dimethylformamide systems. Both strains of R-8 and R-9 also show higher
desulfurization activities toward other sulfur-substrates, indicating that they have
greater desulfurization potential in application.

Key words: biodegradation, biodesulfurization, dibenzothiophene, bacteria strain