In situ enzymatic biofunctionalization of ultrafiltration membranes for enhanced lipase-induced lipid fouling control

Membrane in situ coating design using a filtration unit with lipase and chitosan recirculation, which results in chitosan polyelectrolyte coating and lipase crosslinking for lipid fouling layer hydrolysis. Membrane filtration is widely used in water treatment due to its high separation efficiency. However, membrane fouling remains a major challenge, limiting its global spread. Currently, fouling mitigation relies mainly on membrane cleaning. This study proposes a shift from fouling removal to prevention through enzymatic membrane biofunctionalization. Enzymes are used in cleaning-in-place as effective organic matter catalysts. Immobilizing them on the membrane is suggested to catalyze foulants before a stable fouling layer is formed. For a practical application, this study suggests a shift from membrane modification during the manufacturing process to modification in situ. Lipase from Candida rugosa was immobilized on self-prepared polyethersulfone flat-sheet membranes via crosslinking to a thin chitosan polyelectrolyte layer. Dynamic coating conditions using a filtration unit and the immobilization procedure were optimized, achieving enzymatic activity exceeding 300 U m−2 within 1 h of coating. Oil emulsion filtration experiments revealed a significant reduction in irreversible fouling, meaning that reversible fouling could be easily removed by crossflow rinsing. The nontoxic nature of the coatings indicated a potential suitability as substrates for controlled biofilm-based membrane systems in biological treatment applications. The proposed lipase biofunctionalized membranes show potential for advanced treatment of fatty wastewater through active lipid catalysis.