Desulfurization of light gas oil in immobilized-cell systems of Gordona spCYKS1 and Nocardia sp CYKS2

Desulfurizations of a model oil (hexadecane containing dibenzothiophene (DB T)) and a diesel oil by immobilized DBT-desulfurizing bacterial strains, Go rdona sp. CYKS1 and Nocardia sp. CYKS2, were carried out. Celite bead was u sed as a biosupport for cell immobilization. Seven-eight cycles of repeated -batch desulfurization were conducted for each strain. Each batch reaction was carried out for 24 h. In the case of model oil treatment with strain CY KS1, about 4.0 mM of DBT in hexadecane (0.13 g sulfur l(oil)(-1)) was desul furized during the first batch, while 0.25 g sulfur l(oil)(-1) during the f inal eighth batch. The mean desulfurization rate increased from 0.24 for th e first batch to 0.48 mg sulfur l(dispersion)(-1) h(-1) for the final batch . The sulfur content in the light gas oil was decreased from 3 to 2.1 g l(o il)(-1) by strain CYKS1 in the first batch. The mean desulfurization rate w as 1.81 mg sulfur l(dispersion)(-1) h(-1), which decreased slightly when th e batch reaction was repealed. No significant changes in desulfurization ra te were observed with strain CYKS2 when the batch reaction was repeated. Wh en the immobilized cells were stored at 4 degrees C in 0.1 M phosphate buff er (pH 7.0) for 10 days, the residual desulfurization activity was about 50 similar to 70% of the initial value. (C) 2000 Published by Elsevier Scienc e B.V. All rights reserved.