Biodesulfurization using thermophilic bacteria and identification of bds genes

点击翻译按钮获取中文摘要

Recalcitrant organosulfur compounds such as dibenzothiophene (DBT) derivatives in light gas oil (LGO) cannot be removed by hydrodesulfurization using metallic catalysts. The thermophilic bacteria, Bacillus subtilis WU-S2B and Mycobacterium phlei WU-F1, were isolated for its ability to grow on DBT as the sole source of sulfur at 50℃. In addition to DBT, WU-S2B and WU-F1 also could desulfurize alkylated DBTs such as 4, 6-dimethyl DBT through a sulfur-specific degradation pathway with the selective cleavage of carbon-sulfur bonds. Moreover, when resting cells of WU-F1 were incubated at 45℃ with two types of hydrodesulfurized LGOs in the reaction mixtures containing 50%(v/v)oils, the biodesulfurization reduced the sulfur contents from 120 to 50 ppm S (F-LGO) and from 34 to 15 ppm S (X-LGO), respectively. Gas chromatography analysis with an atomic emission detector revealed that the peaks of alkylated DBTs including 4-methyl DBT, 4, 6-dimethyl DBT, and 3, 4, 6-trimethyl DBT significantly decreased after the biodesulfurization. The DBT-desulfurization genes, bdsABC, were cloned from these two bacteria, and the flavin reductase genes, frb and frm, were also cloned from WU-S2B and Wu-F1, respectively. The recombinant WU-F1 carrying one more set of bdsABC and frm was constructed, and the desulfurizing activity of the recombinant strain was 2. 2-fold higher than that of the wild type strain WU-F1.