Dead biomass of Amazon yeast: A new insight into bioremediation and recovery of silver by intracellular synthesis of nanoparticles

ABSTRACT

This investigation was undertaken to describe a natural process for the removal of silver and the simultaneous recovery of Ag/Ag₂O nanoparticles by dead biomass of the yeast Rhodotorula mucilaginosa. The removal of silver ions from aqueous solution and the synthesis of Ag/Ag₂O nanoparticles were analyzed based on physicochemical factors and equilibrium concentration, combined with transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy (FTIR). A successful process for the synthesis of Ag/Ag₂O nanoparticles was obtained, following the Langmuir isotherm model, showing a high biosorption capacity of silver (49.0 mg g⁻¹). The nanoparticles were spherical, had an average size of 11.0 nm, were synthesized intracellularly and capped by yeast proteins. This sustainable protocol is an attractive platform for the industrial-scale production of silver nanoparticles and of a silver nanobiosorbent.

KEYWORDS:

• Bioremediation
• biosynthesis
• dead biomass
• intracellular
• metal mine
• nanoparticles
• Rhodotorula mucilaginosa
• silver
• yeast

Acknowledgements

The authors are thankful to the Laboratory of Photoelectron Spectroscopy (LEFE), Universidade Estadual Paulista “Júlio de Mesquita Filho” (UNESP), Araraquara, São Paulo, Brazil for the performing the XPS analysis in this research work.

Funding

This work was supported by the Company Vale S/A, bank BNDES (Banco Nacional do Desenvolvimento) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP grant 2016/04364-5).