Detoxification of hexavalent chromate by growing Paecilomyces lilacinus XLA.

In the study, the capability of Paecilomyces lilacinus XLA (CCTCC: M2012135) to reduce Cr and its main antagonistic mechanisms to Cr were experimentally evaluated. Activated growing fungus XLA efficiently reduced over 90% Cr in the media with Cr concentration below 100 mg L at pH 6 after 14 days. After 1-day exposure to 100 mg L Cr, nearly 50% of Cr was reduced. Moreover, SO stimulated Cr reduction, whereas other interferential ions inhibited Cr reduction. The interaction mechanisms between XLA and Cr mainly involve biotransformation, biosorption, and bioaccumulation, as detected by electron microscopy and chemical methods. The lower concentrations of Cr (5 and 50 mg L) stimulated the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) level in XLA, respectively, but the higher concentration of Cr (150 mg L) decreased the enzymatic activities and GSH concentration. The results implied that SOD, CAT and GSH were defensive guards to the oxidant stress produced by Cr. All these extracellular/intracellular defense systems endowed XLA with the ability to resist and detoxify Cr by transforming its valent species. The fungus XLA could efficiently reduce Cr under different environmental conditions (pH, interferential ions, and concentration). Moreover, XLA could endure the high concentration of Cr probably due to its high biotransformation capability of Cr and intracellular antioxidant systems for the detoxification of ROS generated by external Cr. All these results suggested that the fungus XLA can be applied to remediation of Cr-contaminated environments.