Genomic and proteomic analyses reveal the reduction mechanism of hexavalent chromium by the culturing supernatant of strain Pediococcus acidilactici 13-7

This study used lactic acid bacteria with high antioxidative properties to screen for strains capable of reducing hexavalent chromium [Cr (VI)] in their culturing supernatants. The strain Pediococcus acidilactici 13-7 exhibited potent Cr (VI)-reducing capability and remarkable resistance to Cr (VI) even at concentration as high as 24 mM. Comparative genomics analysis revealed a unique gene, ChrR, associated with Cr (VI) reduction in this strain, distinguishing it from four reference strains of P. acidilactici. The proteomic investigation identified proteins linked to the ChrR gene, such as nqo1, frdA, and gshR, indicating significant enrichment in redox-related functions and oxidative phosphorylation pathways. These findings suggest that P. acidilactici 13-7 possesses superior electron transfer capacity compared to other strains, making it more adaptable under highly oxidative conditions by modulating the external environment to mitigate oxidative stress. Collectively, the results demonstrated the potential application of this lactic acid bacterial strain for bioremediation of heavy metals by its ability to reduce Cr (VI), and shed light on the molecular mechanisms underlying Cr (VI) reduction of the strain P. acidilactici 13-7. Cr(VI) has been considered as one of the top toxic pollutants to the aqueous environment. Microorganisms have emerged as a sustainable alternative for the bioremediation of Cr (VI). In the present study, we screened a lactic acid bacterium strain P. acidilactici 13-7, and the culturing supernatants of which has a potent Cr (VI)-reducing capability. This would thus enable the development of a novel method for reducing Cr (VI) using the culturing broth of lactic acid bacteria without relying on the presence of the bacteria per se, thereby expanding the scope of the application of microorganisms in Cr (VI) treatment.