Enhanced arsenic removal from aqueous medium by arsenic tolerant groundwater fungi

ABSTRACT

Aim: Arsenic concentration in groundwater above the acceptable level is of global concern due to its serious human health effects. Application of certain fungi, due to their amazing skill to remove arsenic from arsenic contaminated water has received attention in recent years. The main aim of this study was to isolate arsenic tolerant fungi from arsenic-contaminated groundwater and assess their ability for arsenic removal from the aquatic system in-vitro.Methodology: Fungi were isolated from arsenic-contaminated groundwater (44.9–161.1 mg l-1). An experiment on bioremediation/ removal of arsenic by selected highly arsenic tolerant fungi was conducted by culturing them in arsenic supplemented medium and measuring the arsenic contents in initial and after incubation with fungi using Hydride Generation Atomic Absorption Spectroscopy (HG-AAS) to find out the arsenic removal percentage. Results: In all, ten out of forty-five fungi obtained from highly arsenic-contaminated groundwater (44.9–161.1 mg l-1) were able to remove high arsenic contents (>80%) from liquid medium with >85% arsenite (by 6 fungal isolates) and >85% of arsenate (by 9 fungal isolates). In arsenic tolerance assay, all 10 test fungi grew readily in liquid medium enriched with either arsenate (10 and 20 g l-1) or arsenite (2 g l-1) under laboratory conditions (27±2°C). These fungi showed log phase between 5 to 10 days with stationary phase of 11-15 days. High arsenite concentration (4 g l-1) however, completely inhibited the growth of 50% of these fungal isolates. Five of these isolates showed high tolerance index pattern (0.97- 0.91) as compared to others (0.22–0.13). These fungi greatly altered the pH of arsenic supplemented liquid medium (10 mg l-1) as compared to the control when they were individually cultured. These arsenic tolerant fungal isolates may effectively be used for the bioremediation of arsenic from groundwater. Interpretation: The study suggested that 10 fungal isolates were able to tolerate high arsenic concentrations (20 g l-1 of arsenate and 2 g l-1 of arsenite) and were able to enhance arsenic removal (more than 80%) in liquid medium at neutral pH (7.0) and 27°C temperature.