Cellulose–Alginate Biohybrid Cryogels for Efficient Methyl Orange Dye Removal

High Resolution Image Download MS PowerPoint Slide The uncontrolled discharge of synthetic dyes into aquatic environments poses severe environmental and public health risks due to their high stability, persistence, and toxicity. Moreover, most existing treatment technologies are inefficient, costly, or unsustainable for recalcitrant dyes, particularly azo dyes, underscoring the need for innovative materials that can enhance remediation performance. In this context, the development of sustainable, polymer-based materials that integrate physical adsorption with biological degradation properties represents a promising strategy. Herein, we report a sustainable biohybrid platform based on the immobilization of Cunninghamella elegans within a cellulose microfibril/sodium alginate cryogel. The bioengineered cryogel scaffold exhibits high porosity, structural stability, and enhanced mass–transfer properties, enabling efficient nutrient diffusion and fungal viability within the polymer matrix. The resulting biohybrid system achieved complete removal of methyl orange (5–20 ppm) from water samples, outperforming free fungal cells and displaying enhanced apparent kinetic constants at elevated dye concentrations. Control experiments confirmed the intrinsic adsorption contribution of the polymeric matrix, while UHPLC–ESI–MS/MS analysis identified the main biotransformation products consistent with fungal reductive amination pathways. Recyclability assays demonstrated sustained removal efficiencies above 90% over multiple cycles, highlighting operational robustness. These findings demonstrate that cellulose/alginate cryogels provide a recyclable, high-performance, and environmentally friendly support for microbial immobilization, offering a promising polymer-based strategy for sustainable dye remediation in water treatment systems.