Five strains of Rhodotorula mucilaginosa were tested for the ability to accumulate free and complexed silver ions by metabolism-dependent and -independent processes. The ability to take up Ag+ was observed in both live and dead biomass, whereas silver dicyanide [Ag (CN)2-] uptake was strictly glucose dependent. In contrast to Ag (CN)2-, glucose addition inhibited by 16 to 25% the Ag+ uptake rate of living UFMG - Y02, Y27, and Y35 cells, while strains CBS 316 and UFMG-Y01 showed an improved uptake rate of about 115% and 13%, respectively. The Langmuir sorption model was used to evaluate the silver sorption capability of the R. mucilaginosa strains. The calculated q max value suggested that R. mucilaginosa strains UFMG-Y27 had the highest loading capacity. The type strain CBS 316 had the lowest q max but showed the highest affinity for silver ions. The results provided by the Fourier Transform Infra Red analysis (FTIR) suggest that C=O groups represent the main reactive site for silver uptake by the strain UFMG-Y27.
Bioaccumulation; biosorption; Rhodotorula mucilaginosa; silver
