Biofilm Formation and Detoxification of Hexavalent Chromium by <i>Bacillus subtilis</i>: A Sustainable Approach to Bioremediation

Hexavalent chromium [Cr(VI)] is a toxic environmental pollutant, primarily generated by industrial processes, posing a significant risk to biota. Effective detoxification of Cr(VI) is necessary before environmental discharge. This study focused on the Cr(VI) tolerance and detoxification potential of an isolated Bacillus subtilis strain KCBA07C10, along with the effects of Cr(VI) stress on its biofilm formation, and its potential application in bioremediation. The bacterial strain isolated from treated textile effluent, was subjected to growth studies in Cr(VI)-supplemented media with a low carbon source. Detoxification potential was assessed through Cr(VI) and total Cr removal analyses, while biofilm formation was evaluated using spectrophotometric assays and scanning electron microscopy. Results revealed that B. subtilis KCBA07C10 tolerates high Cr(VI) concentrations (> 16.0 mg/L) and achieves significant detoxification via bioreduction, removing nearly 88% of Cr(VI) even under nutrient-limited conditions. These findings highlight the strain's potential for bioremediation. Furthermore, quantitative assays demonstrated a positive correlation between Cr(VI) exposure and biofilm formation (p = 0.009, α = 0.05), suggesting an adaptive defense mechanism. This study highlights the potential of B. subtilis KCBA07C10 as an eco-friendly agent for Cr(VI) detoxification and bioremediation applications.