Abstract
Removal of toxic Cr(VI) by microbial reduction is a promising approach to reducing its ecotoxicological impact. To develop bioremediation technologies, many studies have evaluated the application of microorganisms isolated from Cr(VI)-contaminated sites. Nonetheless, little attention has been given to microbes from the environments without a history of Cr(VI) contamination. In this study, we aimed to characterize the Cr(VI) tolerance and removal abilities of a filamentous fungus strain, SL2, isolated from indoor air. Based on phenotypic characterization and rDNA sequence analysis, SL2 was identified as Penicillium oxalicum, a species that has not been extensively studied regarding Cr(VI) tolerance and reduction abilities. SL2 showed high tolerance to Cr(VI) on solid and in liquid media, facilitating its application to Cr(VI)-contaminated environments. Growth curves of SL2 in the presence of 0, 100, 400, or 1000 mg/L Cr(VI) were well simulated by the modified Gompertz model. The relative maximal colony diameter and maximal growth rate decreased as Cr(VI) concentration increased, while the lag time increased. SL2 manifested remarkable efficacy of removing Cr(VI). Mass balance analysis indicated that SL2 removed Cr(VI) by reduction, and incorporated 0.79 mg of Cr per gram of dry biomass. In electroplating wastewater, the initial rate of Cr(VI) removal was affected by the initial contaminant concentration. In conclusion, P. oxalicum SL2 represents a promising new candidate for Cr(VI) removal. Our results significantly expand the knowledge on potential application of this microorganism.
Highlights
Chromium (Cr) is a cause for considerable environmental concern because of its improper release into the environment from anthropogenic activities [1, 2]
This study provides a new candidate for Cr(VI) removal, and the results significantly expand our knowledge on the utility of this microorganism
P. oxalicum SL2, isolated from indoor air, was found to tolerate a high Cr(VI) concentration on solid and in liquid media, and this property may facilitate its application to Cr(VI)-contaminated environments
Summary
Chromium (Cr) is a cause for considerable environmental concern because of its improper release into the environment from anthropogenic activities [1, 2]. Controlling the chemical state of Cr is vital for reducing its ecotoxicological impact. Cr mainly exists as Cr (VI) and Cr(III) compounds [3], which differ in their mobility and toxicity [4]. Cr(VI) compounds are water soluble in the full pH range and are toxic to humans [5, 6], animals [7], plants [8], and microorganisms [9], whereas Cr(III) compounds are less water soluble and serve as essential nutrients for energy metabolism [10]. Reducing Cr(VI) to Cr(III) can minimize its harm to the environment and human health.
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