Isolation of Soil Bacteria Species for Degrading Dibenzothiophene

<正>Five bacterial strains, which are able to grow and to disintegrate dibenzothiophene (DBT) and diben-zothiophene 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 Pseu-domonas 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