Study of Baijiu Distiller’s Grains Leachate as an Efficient Co-Substrate Enhance the Biodegradation of Azo Dyes by Providencia rettgeri

Bioremediation has gained significant attention due to its potential to remove azo dyes. However, the challenges microorganisms face in surviving when azo dyes are the sole carbon source limit its widespread application. This study aimed to improve the biodegradation of azo dyes by utilizing Baijiu distiller’s grains leachate (BDGL) as a co-substrate. The experimental results demonstrated that BDGL significantly enhanced Providencia rettgeri’s ability to degrade the model pollutant Acid Black 210 (AB210), achieving a decolorization efficiency of 94.5%. This may be attributed to the nutrient-rich composition of BDGL, which includes ethanol and protein, providing a favorable substrate for bacterial growth and activity. The higher biomass and increased activities of azoreductase and quinone oxidoreductase in the BDGL group further supported these findings. Additionally, this method demonstrated broad-spectrum degradation of azo dyes (Direct Red 5B, Acid Red 73, and Congo Red) with different structures, highlighting its potential applicability. Metabolite assays combined with transcriptomics analyses revealed that the expression of functional genes related to redox reactions, azo bond cleavage, and hydrolysis increased under the co-metabolic conditions of BDGL, resulting in stronger reducing power that further mineralized the dye into smaller metabolites. Our study offers a practical strategy for the simultaneous treatment of dye-containing wastewater and Baijiu distiller’s grains, with significant environmental and industrial applications.