Immobilization of the bacterium Pseudomonas stutzeri UP-1 was isolated from soil and sewage in the Shengli Oilfield. Biodesulfurization (BDS) of dibenzothiophene (DBT) was carried out using immobilized P. stutzeri UP-1 (CGMCC No. 0974) in model system. The results show that sodium alginate (SA) is an appropriate material of immobilization. The optimized operation immobilization condition was 4 degrees C; the concentration of SA was 3% (w/v); and the ratio of SA (ml) to cells (g) was 20. The stability and life-time of immobilized cells were much better than those of the non-immobilized cells. The life-time of immobilized cells could reach 600 h by reactivation. (c) 2005 Elsevier Ltd. All rights reserved.