Jh. Chang et al., Production of a desulfurization biocatalyst by two-stage fermentation and its application for the treatment of model and diesel oils, BIOTECH PR, 17(5), 2001, pp. 876-880
For the production of oil-desulfurizing biocatalyst, a two-stage fermentati
on strategy was adopted, in which the cell growth stage and desulfurization
activity induction stage were separated. Sucrose was found to be the optim
al carbon source for the growth of Gordonia nitida CYKS1. Magnesium sulfate
was selected to be the sulfur source in the cell growth stage. The optimal
ranges of sucrose and magnesium sulfate were 10-50 and 1-2.5 g L-1, respec
tively. Such a broad optimal concentration of sucrose made the fed-batch cu
lture easy, while the sucrose concentration was maintained between 10-20 g
L-1 in the actual operation. As a result, 92.6 g L-1 of cell mass was acqui
red by 120 h of fed-batch culture. This cell mass was over three times high
er than a previously reported result, though the strain used was different.
The desulfurization activity of the harvested cells from the first stage c
ulture was induced by batch cultivation with dibenzothiophene as the sole s
ulfur source. The optimal induction time was found to be about 4 h. The res
ting-cell biocatalyst made from the induced cells was applied for the deep
desulfurization of a diesel oil. It was observed that the sulfur content of
the diesel oil decreased from 250 mg-sulfur L-oil(-1) to as low as 61 mg-s
ulfur L-oil(-1) in 20 h. It implied that the biocatalyst developed in this
study had a good potential to be applied to a deep desulfurization process
to produce ultralow-sulfur fuel oils.