Degradation of Carbazole by Microbial Cells Immobilized in Magnetic Gellan Gum Gel Beads
Degradation of Carbazole by Microbial Cells Immobilized in Magnetic Gellan Gum Gel Beads
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DOI：
10.1128/aem.01051-07
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发表时间：
2007-09
影响因子：
4.4
通讯作者：
Xia Wang;Zhonghui Gai;Bo Yu;Jinhui Feng;Changyong Xu;Yong Yuan;Zhixin Lin;P. Xu
中科院分区：
文献类型：
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作者：
Xia Wang;Zhonghui Gai;Bo Yu;Jinhui Feng;Changyong Xu;Yong Yuan;Zhixin Lin;P. Xu
多环芳香族杂环化合物，如咔唑，是一种被怀疑对人类健康构成威胁的环境污染物。本实验研究了固定化鞘氨单胞菌XLDN2-5细胞对咔唑的降解作用。对4种聚合物作为鞘氨单胞菌XLDN2-5的固定化载体进行了评价。通过与琼脂、海藻酸盐和κ-卡拉胶的比较，选择结冷胶作为最佳的固定化载体。采用共沉淀法制备了Fe3O4纳米颗粒，平均粒径约为20 nm，饱和磁化强度为49.65 g−1。以结冷胶与纳米Fe3O4的混合物为固定载体，采用离子化法制备了磁固定细胞。采用游离细胞、非磁固定化细胞和磁固定化细胞在水相进行生物降解实验。结果表明，磁固定细胞比非磁固定细胞和游离细胞具有更高的咔唑生物降解活性。当Fe3O4纳米颗粒浓度为9 mg ml−1，磁固定细胞的饱和磁化强度为11.08 emu g−1时，生物降解活性最高。此外，回收实验表明，在8次循环中，磁固定细胞的降解活性逐渐提高。这些结果支持了利用磁固定细胞开发高效的生物催化剂，并为改进生物催化剂用于咔唑和其他有害有机化合物的生物降解提供了一种有前途的技术。
ABSTRACT Polycyclic aromatic heterocycles, such as carbazole, are environmental contaminants suspected of posing human health risks. In this study, we investigated the degradation of carbazole by immobilized Sphingomonas sp. strain XLDN2-5 cells. Four kinds of polymers were evaluated as immobilization supports for Sphingomonas sp. strain XLDN2-5. After comparison with agar, alginate, and κ-carrageenan, gellan gum was selected as the optimal immobilization support. Furthermore, Fe3O4 nanoparticles were prepared by a coprecipitation method, and the average particle size was about 20 nm with 49.65-electromagnetic-unit (emu) g−1 saturation magnetization. When the mixture of gellan gel and the Fe3O4 nanoparticles served as an immobilization support, the magnetically immobilized cells were prepared by an ionotropic method. The biodegradation experiments were carried out by employing free cells, nonmagnetically immobilized cells, and magnetically immobilized cells in aqueous phase. The results showed that the magnetically immobilized cells presented higher carbazole biodegradation activity than nonmagnetically immobilized cells and free cells. The highest biodegradation activity was obtained when the concentration of Fe3O4 nanoparticles was 9 mg ml−1 and the saturation magnetization of magnetically immobilized cells was 11.08 emu g−1. Additionally, the recycling experiments demonstrated that the degradation activity of magnetically immobilized cells increased gradually during the eight recycles. These results support developing efficient biocatalysts using magnetically immobilized cells and provide a promising technique for improving biocatalysts used in the biodegradation of not only carbazole, but also other hazardous organic compounds.