Mechanisms for metal removal established via electron microscopy and spectroscopy: a case study on metal tolerant fungi Penicillium simplicissimum

• Published in: Journal of hazardous materials 2019-01, Vol.362, p.394-402
• Main Authors: Chen, Si Hui, Cheow, Yuen Lin, Ng, Si Ling, Ting, Adeline Su Yien
• Format: Article
• Language: English
• Subjects: Electron microscopy; FTIR; Penicillium simplicissimum; Phytotoxicity; Toxic metals
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2018.08.077

[Display omitted] •Unique study to use SEM-EDX analysis to reveal metal biosorption onto cells.•Novel use of TEM-EDX analysis to indicate metal precipitation via bioaccumulation.•Metal bioaccumulation reduced metal toxicity allowing seedlings to grow.•FTIR analysis showed biosorption of metals by various functional groups.•Live cells of P. simplicissimum removed metals more efficiently. Penicillium simplicissimum (isolate 10), a metal tolerant fungus, tolerated 1000 mg/L Cu and 500 mg/L Zn, but were inhibited by Cd (100 mg/L), evident by the Tolerance Index (TI) of 0.88, 0.83, and 0.08, respectively. Live cells of P. simplicissimum were more effective in removing Cr (88.6%), Pb (73.7%), Cu (63.8%), Cd (33.1%), and Zn (28.3%) than dead cells (5.3–61.7%). Microscopy approach via SEM-EDX and TEM-EDX suggested that metal removal involved biosorption and bioaccumulation, with metal precipitates detected on the cell wall, and in the cytoplasm and vacuoles. FTIR analysis revealed metals interacted with amino, carbonyl, hydroxyl, phosphoryl (except Cd) and nitro groups in the cell wall. Biosorption and bioaccumulation of metals by live cells reduced Cu and Pb toxicity, observed from good root and (4.00–4.28 cm) and shoot (8.07–8.36 cm) growth of Vigna radiata in the phytotoxicity assay.