Immobilization of Phenazine-1-carboxylic Acid on Chitosan/Polyvinyl Alcohol Gel and its Enhancement Effect on the Decolorization of Disperse Red S-R by Shewanella oneidensis

Soluble electron shuttles have been found to facilitate the biodecolorization of azo dyes, yet their loss due to water flow can escalate costs and risk secondary pollution. This issue can be mitigated by immobilizing the shuttles. In this study, we immobilized phenazine-1-carboxylic acid (PCA) using a chitosan/polyvinyl alcohol gel carrier and investigated its effect on the degradation of disperse red S-R (DR S-R) by Shewanella oneidensis FJAT-2478. Both free and immobilized PCA significantly increased the decolorization rate within a 50–400 mg/L concentration range for DR S-R, without affecting the final efficiency. Immobilized PCA was slightly less effective than free PCA (4.18-fold at 100 mg/L DR S-R), but was 3.63-fold more effective than the control group without PCA. It also demonstrated excellent reusability, retaining 83% of its initial activity after 10 cycles. Unlike free PCA, which reduced flavin secretion of FJAT-2478 by 36.4%, immobilized PCA increased it by 19.5%, indicating potential differences in their electron transfer modes. This study highlights the potential of immobilized phenazine-based electron shuttles in biologically decolorizing disperse dye wastewater. Graphical Abstract: (Figure presented.)