Efficient Zn 2+ and Pb 2+ uptake by filamentous fungus Paecilomyces marquandii with engagement of metal hydrocarbonates precipitation

Abstract

Zinc and lead biosorption by living non-growing filamentous fungus Paecilomyces marquandii was examined for its potential application in heavy metals elimination from contaminated areas. Metal uptake by the studied fungus was pH dependent and reached the level of 308 mg of Zn 2+ g −1 and 505 mg of Pb 2+ g −1 at pH of 7.5 caused by microprecipitation in slightly alkaline environment. All other metal studies were cultivated with unregulated pH yielding the maximum of 186.2 mg of Zn 2+ g −1 and 305.8 mg of Pb 2+ g −1. Interestingly, zinc binding by mycelium increased intensively after 15 h of incubation, whereas the lead concentration in biomass extended gradually and proportionally to the initial concentration and the time of contact. The study showed that thermal pretreatment of mycelium led to a decline in metal uptake, especially in the case of zinc. The mycelium slightly digested by the cell wall lytic enzyme complex, could adsorb lead twice as well after 2 h of exposure whereas zinc loading did not differ from the metal uptake by mycelia without any digestion procedure. The release of potassium ions from the mycelium, concomitant with lead uptake was observed suggesting ion exchange participation in lead binding. Energy-dispersive X-ray analysis, X-ray diffraction and FTIR spectroscopy revealed the presence of both metals hydrocarbonates on the mycelium surface. Additionally, the contribution of carboxyl and amide groups, originating from the mycelium, in metal binding was confirmed by FTIR analysis. The obtained results suggest that the effective metals uptake by P. marquandii was due to a combined mechanism with a dominant role of metabolism dependent microprecipitation.