Biosorption of Hexavalent Chromium using Fungal Strains Isolated from Soil

Abstract

Chromium tolerant fungal strains were isolated from heavy metal contaminated environments and identified using morphological and microscopic observation followed by ribotyping. The microorganisms with the maximum tolerance were analyzed by inoculating each fungus in a PD medium supplemented with hexavalent Chromium salts. The presence of the metal was estimated by the acidic reaction with the 1, 5-diphenylcarbazide method using a spectrophotometer (UV – Vis) at 540 nm. Among all the fungal strains, the most tolerant under maximum enrichment was identified as Paecilomyces lilacinus by a zone of inhibition on the PDA medium. The effect of environmental parameters like pH and temperature on the growth and heavy metal removal also were analyzed. Among the fungal strains, Aspergillus niger, A. terreus, and Paecilomyces lilacinus could tolerate Chromium (VI) toxicity up to 800 mgL-1. All the fungi were able to completely remove the heavy metal Cr (VI) at the concentration of 10mg/L, where the maximum growth was obtained. However, the organisms could remove the Chromium in higher concentrations at a slow rate. The maximum removal was recorded at acidic pH (4.0) under ambient temperature (30oC). The fungal species, Paecilomyces lilacinus exposed to UV- radiation for up to 10 minutes, enhanced its bio-sorption efficiency compared to the normal strain.