A Facultative Electroactive Chromium(VI)-Reducing Bacterium Aerobically Isolated From a Biocathode Microbial Fuel...

Area of Science:

• Microbiology
• Environmental Science
• Electrochemistry

Background:

• Hexavalent chromium (Cr(VI)) poses significant environmental and health risks.
• Microbial fuel cells (MFCs) offer a sustainable approach for Cr(VI) remediation.
• Isolation and characterization of electroactive bacteria are crucial for MFC development.

Purpose of the Study:

• To isolate and characterize a novel facultative electroactive bacterium from a Cr(VI)-reducing MFC biocathode.
• To evaluate the Cr(VI)-reducing ability of the isolated strain in different environments.
• To assess the impact of the novel strain on MFC performance for enhanced Cr(VI) removal.

Main Methods:

• Aerobic isolation of a Gram-positive, rod-shaped bacterium (Strain H) from an MFC biocathode.
• 16S rRNA gene sequencing for taxonomic identification, revealing high similarity to *Bacillus cereus*.
• Assessment of Cr(VI) reduction in liquid culture (LB broth) and within an MFC biocathode.
• Measurement of MFC power density and Cr(VI) removal rates.

Main Results:

• Strain H, identified as *Bacillus* sp. (accession MH782060), demonstrated efficient Cr(VI) reduction in both aerobic and anaerobic conditions.
• Cr(VI) removal reached 50.6% in LB broth within 20 hours.
• The Strain H biocathode significantly enhanced MFC performance, achieving a 1.26 times higher power density and 1.75 times higher Cr(VI) removal rate compared to a sterile cathode.

Conclusions:

• A novel Gram-positive *Bacillus* sp. strain (Strain H) was successfully isolated and characterized for its electroactive and Cr(VI)-reducing capabilities.
• The facultative electroactive nature of Strain H makes it a promising candidate for Cr(VI) remediation in MFCs.
• A simple aerobic isolation method can be effective for screening facultative electroactive bacteria for biotechnological applications.