Off The Organic Sulfur Microbial Isolation, Identification And Selection

Biodesulfurization (BDS) can effectually selectively remove the sulfur from condensed thiophenes that is recalcitrant to hydrodesulfurization (HDS), and it is promising process that can be complement or alternative to HDS for deep desulfurization of petroleum and its products.The isolation of strains is precondition of BDS. The selection mutant of strains is an effective method to improve the activity of desulfurization. In this paper, screening and determinant of microbial desulfurization, and the characteristic of strain, the biotransformation conditions of desulfurization were studied systematically.A strain was isolated from polluted soils of Da Qing oil-field with the high ability to desulfurize dibenthiophene (DBT) through the 4S pathway. The morphological properties and 16S rDNA sequence suggested that the isolated strain belongs to the evolution branch of Enterobacter and shows highest homology to Enterobacter sakazaki. The strain was named as Enterobacter sakazakii HDBS-1.A high ability to DBT-desulfurization mutant HDBS-4 has been acquired after the UV mutagenesis, the DES mutagenesis and the UV&DES mutagenesis. The 2-HBP yield detected quantitatively by colorimetry was 0.011726mmol/L, which was 4.5 times than the original yields. The best dosage of mutagenesis was: The irradiation time of ultraviolet was 17s, concentration of DES was 0.3%, mutagenic processing time was 25min. The genetic characteristics were stabile after 10 successive generations of HDBS-4. In order to get higher ability of desulfurization, the optimal desulfurization conditions of HDBS-4 had been studied. By single factor experiments, the conclusion was obtained that the best amounts(/L) of desulfurization medium was: Glycerol 10mL, Yeast extract 2g, DBT 20mg, KH2PO4 2.44g, Na2HPO4·12H2O 12.03,MgCl2·6H2O 0.4g, MnCl2·4H2O 4mg, FeCl3·6H2O 1mg, CaCl2 0.75mg, pH 7.0-7.5. The optimum desulfurization conditions were the the temperature 30℃, the cultures were performed in 250mL flasks with 25mL, 6% of inoculated volume. Under this condition, the 2-HBP yield of HDBS-4 was 0.0359mmol/L, which is 3 times than usual condition and 13 times than that of the original strain HDBS-1.