Analyses of microbial desulfurization reaction of alkylated dibenzothiophenes dissolved in oil phase

Abstract

The kinetics of the oil/water two-phase reaction system was analyzed, and the reaction was carried out with the desulfurization of alkylated dibenzothiophenes (Cx-DBTs) using the desulfurizing microorganism Mycobacterium sp. G3. In the water-phase reaction system, the desulfurization activities were constant with respect to species of Cx-DBTs as substrates. However, the desulfurization activities in the oil/water two-phase reaction system against DBT, 4,6-dimethyl DBT, 4,6-diethyl DBT, 4,6-dipropyl DBT, and 4,6-dibutyl DBT were 49.0, 45.9, 11.5, 1.35, and 0.00 micromol g DCW(-1) h(-1), respectively. The kinetic parameters for the degradation of DBT, 4,6-dimethyl DBT, and 4,6-diethyl DBT were also obtained (V(max) values 90.0, 68.7, and 22.7 micromol g DCW(-1) h(-1) and K(m) values 0.21, 0.70, and 3.03 mM, respectively). The reason for the decrease in activity against Cx-DBTs of high molecular weight was a decrease in the V(max) value and an increase in the K(m) value, the latter being a particularly serious problem. Furthermore, the hydrophobicity of the substrate was evaluated as the capacity factor measured by high-performance liquid chromatography (HPLC). The correlation between substrate hydrophobicity and desulfurization activity indicated that the desulfurization reaction in the oil/water two-phase reaction system is greatly influenced by the hydrophobicity of the substrates. In addition, the influence of the solvent on desulfurization activity was examined, and it was found that not only the hydrophobicity of substrates, but also that of solvents, affected the desulfurization reaction.

De-repression and comparison of oil–water separation activity of the dibenzothiophene desulfurizing bacterium, Mycobacterium sp. G3

“…G3 may be a useful biocatalyst for BDS because it is known to have high desulfurization activity and broad substrate specificity (Okada et al 2001(Okada et al , 2002(Okada et al , 2003. However, transcription of the desulfurization genes is also repressed by sulfur compounds in G3 (Okada et al 2001).…”

Biodesulfurizing Microbes in the Petroleum Refinery Areas of Saudi Arabia

“…Thermophilic bacteria have also been reported showing the 4S pathways. [7][8][9] In 4S pathway, phenolic products are formed as the product [10][11][12][13][14][15][16][17] as shown in Scheme 1. As the accumulation of product increases, the activities of this pathway enzyme get decreased/ceased.…”