Identification of the fungi absorbing heavy metals isolated from waste deposits of zinc factories

Abstract

The disposed wastes of zinc industries contain large amounts of heavy metals such as Pb²⁺ and Cd²⁺. These elements are considered as hazardous elements to human beings and other organisms. This study aims at introducing the fungal isolates that evolved to be compatible with waste deposits during the time and can absorb Pb²⁺ and Cd²⁺ions. During the spring and autumn in 2011, eight samples of sediment contaminated by waste were collected from Zanjan zinc industrial zone and fungal isolates were isolated. The degree of tolerance against 0–2500 mg/L Pb²⁺ and Cd² was measured using minimum inhibitory concentration (MIC) experiment. Results revealed that two <em>Aspergillus</em> sp. isolates namely A.BZ1 isolated in spring and A.PZ1 isolated in the autumn showed the highest resistance and the maximum growth rate. The result of sorption capacity by live and dead biomasses of two isolates against Pb²⁺ and Cd²⁺ions with different metal concentrations showed the highest uptake by living biomassofA.PZ1 with 53.75 mg/g and 7.02 mg/g and minimum adsorption in dead biomass was 3.65 and 0.19 mg/g. The results of contact time on isolates sorption revealed that A.PZ1 with 1.715 mg/g sorption has 72.97 % removal efficiency in the first 30 minutes. After the identification of these two isolates and the combination of morphological criteria and sequencing of the ITS˗rDNA region, the <em>A. fumigatus</em> was identified. The prevalence of isolate population, metal tolerance and the genome information in fungi are three traits that can be used as biomarkers for monitoring contaminants in the environment.