Table 1.
Bacterial growth and protein content of culture medium inoculated with Chelatococcus sp. in presence or absence of DBT (0.5 mM).
A: growth in presence of DBT, B: growth in absence of DBT. Values are mean ± S.D of triplicate determinations. Significance of difference with respect to growth of bacteria in presence of 0.5 mM DBT.
Fig 1.
Phylogenetic relationships of isolated NBTU-06 and other closely related Chelatococcus species based on 16S rRNA sequencing.
The tree was generated using the neighbor-joining method and the sequence from Bacillus sp. HSCC 1649 T (Accession no. AB045097) was considered as out-group. The data set was resampled 1,000 times by using the bootstrap option, and percentage values are given at the nodes.
Fig 2.
Kinetics of utilization of DBT by Chelatococcus sp. in liquid BSM as the sole source of sulfur.
Residual DBT concentration was determined by RP-HPLC analysis of extract from the culture medium (⬛) inoculated with Chelatococcus sp. and uninoculated controls (▲). Values are mean ± SD of triplicate determinations.
Fig 3.
GC-MS analysis of DBT metabolites produced by Chelatococcus sp.
A: GC profile of the culture extract (96 h post inoculation) showing formation of 2- HBP, 2-MBP, and DBTO; B: Mass spectrum of 2-HBP (molecular mass, 170); C: Mass spectrum of 2-MBP (molecular mass, 184).
Fig 4.
GC-MS analysis of metabolites of 4-M- DBT produced by Chelatococcus sp.
A: GC chromatogram of the culture extract showing DBTO, 2-hydroxy-3’ methyl–biphenyl and 4-M- DBT; B: Mass spectrum of DBTO (molecular mass, 200); C: Mass spectrum of 2-hydroxy-3’ methyl—biphenyl (molecular mass, 184); D: Mass spectrum of 4-M- DBT (molecular mass, 198).
Fig 5.
GC-MS analysis of metabolites of 4, 6 -DM- DBT produced by Chelatococcus sp.
A: GC chromatogram of the culture extract showing, 2-hydroxy-3, 3’ dimethyl–biphenyl and 4, 6 -M- DBT; B: Mass spectrum of 2-hydroxy-3, 3’ dimethyl—biphenyl (molecular mass, 198); C: Mass spectrum of 4, 6-DM- DBT (molecular mass, 212).
Fig 6.
Growth performance of Chelatococcus sp. in presence of 0.5 mM DBT in BSM supplemented with different concentrations of 2-HBP or 2-HBP and 2-MBP after 96 h at 37°C.
Values are mean ± SD of triplicate determinations.
Fig 7.
GC–FID chromatogram of desulphurization of diesel oil by Chelatococcus sp.
(A) Control diesel fuel; (B) Diesel fuel treated with Chelatococcus sp. for 24 h at 37°C.
Fig 8.
A scheme for extended 4s pathway of biocatalytic desulfurization of DBT by Chelatococcus sp.