Niazi J H, Karegoudar T B
Department of Biochemistry, Gulbarga University, Gulbarga-595 106, India.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2001;36(6):1135-44. doi: 10.1081/ese-100104137.
A Bacillus sp. which is capable of degrading dimethylphthalate (DMP) was immobilized in calcium alginate and polyurethane foam for efficient and long term degradation of DMP. Freely suspended cells (10(12) cfu ml-1) degraded a maximum of 20 mM DMP. Whereas, alginate-(10(12)cfu g-1 beads) and polyurethane foam-entrapped (0.34 x 10(6-9) cfu g-1 foam cubes) cells degraded a maximum of 40 mM DMP within 12-15 days of incubation. Polyurethane foam-entrapped cells degraded 30 mM of DMP at 4 days and alginate-entrapped cells degraded within 10 to 12 days of incubation irrespective of the cell population. When the initial concentration of DMP increased to 50 mM, the DMP degrading ability of the immobilized cells was not increased even after 20 days. Repeated batch cultures by alginate-entrapped cells with initial 35 mM DMP loading could be reused for a maximum of 20 cycles. However, the degradation rate was gradually decreased when the beads were reused for more than 15 cycles. On the other hand, the foam-entrapped cells, with the same initial DMP loading there was no decrease in DMP degrading ability and could be reused for more than 20 cycles. The packed bed reactor with alginate-entrapped cells (1 x 10(10-12) cfu g-1 bead) could be continuously operated for 7-8 days with an initial 25 mM DMP at a flow rate of 50 ml h-1. Whereas, the polyurethane foam-entrapped cells (1 x 10(6-9) cfu g-1 foam cubes) could be operated continuously for more than 90 days with the same initial DMP loading at a flow rate of 100 ml h-1. Thus the enhanced degradation of DMP could be achieved by immobilizing the cells of Bacillus sp. in calcium alginate and polyurethane foam as compared to that of freely suspended cells.
一株能够降解邻苯二甲酸二甲酯（DMP）的芽孢杆菌被固定在海藻酸钙和聚氨酯泡沫中，以实现对DMP的高效长期降解。游离悬浮细胞（10¹² cfu/ml）最多可降解20 mM的DMP。而海藻酸钙包埋的细胞（10¹² cfu/g珠子）和聚氨酯泡沫包埋的细胞（0.34×10⁶⁻⁹ cfu/g泡沫块）在培养12 - 15天内最多可降解40 mM的DMP。聚氨酯泡沫包埋的细胞在4天内可降解30 mM的DMP，海藻酸钙包埋的细胞在培养10至12天内可降解，与细胞数量无关。当DMP的初始浓度增加到50 mM时，即使在20天后，固定化细胞的DMP降解能力也没有增加。海藻酸钙包埋的细胞对初始加载量为35 mM的DMP进行重复分批培养，最多可重复使用20个循环。然而，当珠子重复使用超过15个循环时，降解速率逐渐降低。另一方面，对于相同初始DMP加载量的泡沫包埋细胞，DMP降解能力没有下降，并且可以重复使用超过20个循环。装有海藻酸钙包埋细胞（1×10¹⁰⁻¹² cfu/g珠子）的填充床反应器，以50 ml/h的流速，初始加载量为25 mM的DMP时，可连续运行7 - 8天。而聚氨酯泡沫包埋的细胞（1×10⁶⁻⁹ cfu/g泡沫块），在相同初始DMP加载量下，以100 ml/h的流速可连续运行超过90天。因此，与游离悬浮细胞相比，将芽孢杆菌的细胞固定在海藻酸钙和聚氨酯泡沫中可实现对DMP的增强降解。
