Bacillus cereus CC-1的亚碲酸盐还原特性及产物表征

Tellurite reduction characteristics of Bacillus cereus CC-1 and product characterization

摘要:

【背景】含Te(IV)的工业废水对于生物体具有潜在的毒性作用，可将Te(IV)还原为Te0的微生物过程具有重要的研究价值。【目的】探索亚硒酸盐还原菌Bacillus cereus CC-1对Te(IV)的还原能力、还原酶位点以及还原产物的特性。【方法】利用前期筛选的亚硒酸盐还原菌Bacillus cereus CC-1还原Te(IV)，根据48 h内还原率大小确定最适Te(IV)浓度及pH；考察不同阴阳离子对Te(IV)还原率的影响与Te(IV)还原酶位点；利用表征分析确定还原产物的组成、结晶性与形貌。【结果】菌株CC-1能够将Te(IV)还原，Te(IV)初始浓度为0.5 mmol/L，体系pH为7.0时还原率最高。体系中外加阴阳离子对Te(IV)的还原有一定影响，其中磷酸根、硫酸根、醋酸根、钼酸盐对Te(IV)的去除无明显影响；低浓度的硝酸根抑制Te(IV)的去除，随着硝酸根浓度增加，其对Te(IV)的去除的抑制作用减弱；铅离子和铋离子对Te(IV)的还原有抑制作用；铜离子能够提高Te(IV)的去除率。在胞外、细胞膜组分以及细胞内均检测到Te(IV)还原酶的活性，且细胞外的酶活高于细胞内和细胞膜上。菌株CC-1可将Te(IV)部分还原为碲单质，还原产物包裹在细胞内部；胞内酶对Te(IV)的还原产物为成簇的碲纳米片。【结论】菌株CC-1具有一定的Te(IV)耐受能力和还原能力，并体现了一定的pH依赖性。菌株CC-1对Te(IV)的还原涉及到多种转运过程，硝酸盐还原酶在Te(IV)还原的过程中可能起到重要作用。菌株CC-1的胞内碲还原酶对Te(IV)的还原产物为胶体Te0，回收和利用较为方便。

Abstract:

[Background] The industrial wastewater containing Te(IV) has potential toxic effects on organisms. The microbial mediated Te(IV) reduction to Te0 is of great importance. [Objective] Exploring the reducing ability, reductase site and reducing product characteristics of Te(IV) by Bacillus cereus CC-1. [Methods] Te(IV) was reduced by a selenite reducing bacterium Bacillus cereus CC-1. The optimum Te(IV) concentration and pH were confirmed according to the reduction rate within 48 h. The Te(IV) reductase site and the reduction ratio of Te(IV) with the existence of different anions and cations were determined. The composition, crystallinity and morphology of the reduced product of Te(IV) were characterized. [Results] Bacillus cereus CC-1 has the Te(IV) reducing ability. The reduction rate was the highest when the initial concentration of Te(IV) was 0.5 mmol/L and at pH 7.0. The addition of anions and cations in the system has a certain effect on the reduction of Te(IV). Phosphate, sulfate, acetate and molybdate have no obvious effect on the removal rate. Low concentration of nitrate inhibits the remove of Te(IV). Lead and bismuth inhibit the reduction of Te(IV) and copper can increase the removal rate of Te(IV). Te(IV) reductase is active both inside and outside of the cell and on the cell membrane, and the extracellular enzyme activity is higher than the other two sites. The strain CC-1 can partially reduce Te(IV) to tellurium, and the reduction product is encapsulated inside the cell. The reduction product of the intracellular enzyme to Te(IV) is a cluster of flaky structure. [Conclusion] The strain CC-1 has Te(IV) tolerance and reducing ability, and shows a certain pH dependence. There may be multiple transport processes for the reduction of Te(IV) by strain CC-1, and nitrate reductase may play an important role in the process of Te(IV) reduction. Te(IV) reductase is not only present on both inside and outside of the strain CC-1 cells but on the cell membrane as well. The reduction of Te(IV) by intracellular enzyme makes recycling and re-using of Te0 possible.