Abstract:

Immobilization of the bacterium Rhodococcus erythropolis DS-3 cells, which was isolated from the oil-soaked soil of Gudao oilfield and could decompose dibenzothiophene (DBT) by 4S pathway, was studied.The effects of immobilization conditions on the bacterium’s bio-desulfurization characteristics and on desulfurization of diesel fuel were investigated.The results showed that the immobilized cells with sodium alginate and polyvinyl alcohol as the immobilized carrier and 1 mmol·L^-1 dimethyl sulfoxide as the culture medium showed good bio-desulfurization characteristics and long natural life.The optimum immobilized condition was 4℃ crosslinking temperature with the concentrations of sodium alginate 2%, polyvinyl alcohol 8%,cells to mixed carrier ratio 0.1 g·ml^-1 and calcium chloride content 2%.After three cycles of circulated desulfurization, the content of DBT decreased from 0.5 to 0.011 mmol·L^-1, the overall rate of desulfurization was 93%, and the average desulfurization efficiency was about 0.225 mg DBT ·(g DCW)^-1·h^-1.The refined diesel fuel with sulfur content 340 mg·L^-1 could be desulfurized by immobilized cells to a low sulfur content of 42 mg·L^-1.Furthermore, the reuse and life periods of immobilized cells were much better than unimmobilized cells.The life periods of the reactivated immobilized cells reached more than 250 h.DS-3 could utilize alcohol, saturated aliphatic alkane which has a C₈—C₁₅ carbon chain as its sole carbon source, but could not utilize cycloalkane, aromatic hydrocarbon and saturated aliphatic alkane which has a carbon chain shorter than hexane or longer than hexadecane.The preference of carbon source was in the order of ethanol, glucose and alkane.GC-FID analysis of refined diesel fuel before and after bio-desulfurization showed that the composition of alkane had little change during bio-desulfurization.It was indicated that the desulfurization of DS-3 specifically cut carbon sulfur bond but had no effect on alkane.

摘要：

从孤岛油田油浸土壤中筛选得到能降解二苯并噻吩(DBT)的红平红球菌DS-3, 对其进行了固定化研究.选取海藻酸钠(SA〖DK〗)-聚乙烯醇(PVA)为包埋固定化载体, 以1 mmol·L^-1二甲基亚砜培养菌体, 固定化最佳操作条件为4℃交联, 8%PVA和2%SA混合, 细胞在胶液中的浓度为0.1 g·ml^-1, 氯化钙含量为2%,此时固定化细胞不但具有良好的脱硫性能, 而且脱硫重复性好, 其寿命可以达到250 h以上.固定化细胞在3次循环后能使模拟柴油中的DBT含量从0.5 mmol·L^-1降至0.011 mmol·L^-1, 总脱硫率达到93％, 平均脱硫效率约为0.225 mg DBT· (g DCW)^-1·h^-1.同样条件下能将精制柴油的硫含量由340 mg·L^-1降到42 mg·L^-1, 总脱硫率为87.64%.DS-3能利用醇类、饱和的C₈～C₁₅脂肪烃, 但不能利用环烷烃、芳香烃、小于C₈或大于C₁₅的脂肪烃, DS-3优先利用碳源的顺序是乙醇、葡萄糖和烷烃.脱硫前后的精制柴油经GC-FID分析证实, 固定化细胞对C—S键具特异性, 不降低柴油的热值.