Reduction and Removal Mechanism of Cr(VI) by a Novel Penicillium Rubens LR6

Bioreduction of Cr(VI) is an efficient and environmentally friendly remediation method. In this study, we isolated and screened a strain of Penicillium rubens LR6 that could tolerate to Cr(VI) and investigated its mechanism for removing Cr(VI). We ascertained the factors affecting the ability of strain to remove Cr(VI) through batch experiments. The results revealed that the strain could effectively remove high concentrations of Cr(VI) and exhibit excellent removal efficiency under different environmental conditions. The removal of Cr(VI) by the strain could be accurately explained by the exponential decay equation, where approximately 9.45% of the Cr was immobilized on the microorganisms. We further investigated the ability of different cell fractions to remove Cr(VI) and found that bioreduction was the primary mechanism involved. This was supported by SEM and TEM analyses, which showed the presence of Cr on the surface and inside the cells. Additionally, XPS analysis confirmed the presence of both Cr(VI) and Cr(III) on the cell surface, and FTIR analysis suggested the involvement of amino, carboxyl, and hydroxyl groups in the reduction and fixation of Cr(VI) on the cell surface. The findings offer a novel technique for bioremediation of Cr(VI)-contaminated wastewater in weakly acidic to weakly alkaline and high salinity environments, providing potential solutions for remediating chromium-contaminated environments.