Identification of a Rhodotorula taiwanensis strain capable of removing Mn(Ⅱ)

Abstract:

[Objective] To investigate the removal efficiency and mechanism by a strain of Rhodotorula. [Methods] The strain was identified based on the morphological characteristics and the phylogenetic tree based on 26S rRNA gene sequences. Then, the removal effect of the strain on Mn(II) was studied at different initial pH and Mn(II) concentrations. Finally, the products were characterized by scanning electron microscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy. [Results] The isolate was identified as Rhodotorula taiwanensis, which could grow well at pH 2.0 and 2 000 mg/L Mn(II). The removal rate of Mn(Ⅱ) by the strain reached 98.52% at the initial pH 6.0 and Mn(II) concentration of 300 mg/L after 144 h, while higher concentrations (≥500 mg/L) of Mn(II) caused toxicity to the cells and weakened the removal effect. The strain could oxidize Mn(II) to manganese oxides (mainly amorphous MnO₂, Mn₂O₃, and MnO), which produced layered minerals accumulated on the cell surface. In addition, the process of removing Mn(II) by the strain increased the pH of the medium (initial pH 7.0, Mn(II) concentration of 100 mg/L) up to 8.4 after 144 h. [Conclusion] R. taiwanensis MF4 isolated in this study can tolerate low pH and high concentrations of Mn(II), remove Mn(II), and increase medium pH. The findings have a reference value for the end process design in the remediation and treatment of acid mine drainage.