Biodesulfurization of hydrodesulfurized diesel oil with Pseudomonas delafieldii R-8 from high density culture

Biodesulfurization (BDS) process of hydrodesulfurized diesel oil by Pseudomonas delafieldii R-8 was studied. Twenty-five grams (dry cell) l−1 of cell density was obtained by production of P. delafieldii R-8. The desulfurization activity of cells grown in logarithmic and stationary phases is higher than that of cells grown in other phases. The maximal desulfurization rate can reach 0.33 mg g−1 h−1 during the first 4 h. The metabolites do not affect desufurization activity of diesel oil. Cell suspension grown at stationary phase was directly mixed with diesel oil, and had a high desulfurization activity as 0.32 mg g−1 h−1 during the first 4 h. In a 5-l fermentor, 500 ml of diesel oil was added when desulfurized cells grown in a stationary phase and the total sulfur was reduced to 313 from 591 mg l−1. Thus, the BDS process can be simplified by directly mixing cell cultivation suspension with diesel oil.