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

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.