A Multienzyme Magnetic Nanocatalyst for Efficient, Sustainable Hydrolysis of Wastewater-Grown Microalgae Consortia

The rigid cell walls of microalgal consortia (Scenedesmus and Tribonema) hinder the efficient release of intracellular bioproducts and present a significant challenge for sustainable biomass utilization. To address this challenge, a novel multienzyme magnetic nanocatalyst (ME-MNC) was synthesized to enhance enzymatic hydrolysis. It comprised cellulase, α-amylase, amyloglucosidase, and alcalase immobilized on amino-functionalized iron oxide nanoparticles. Optimization using Central Composite Design identified optimal parameters: 103.82 mM glutaraldehyde, 178.79 min cross-linking time, and 7.08 h immobilization time. The catalytic system demonstrated enzyme activity recoveries of 64.66% (cellulase), 67.02% (α-amylase), 43.40% (amyloglucosidase), and 81.14% (alcalase). Structural and physicochemical characterizations, including X-ray diffraction, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and thermogravimetric analysis, confirmed successful synthesis and enzyme immobilization. Under optimal conditions, the ME-MNC achieved 81.7% sugar recovery, exceeding the yield of the free enzyme mixtures (69.5%), and maintained stable performance across pH 6-8 and temperatures of 50-60 °C. After five reuse cycles, the catalyst retained 81% sugar recovery and 96% protein recovery, underscoring its efficiency and reusability. This reusable catalyst offers a sustainable and scalable strategy for microalgal biomass conversion, enabling efficient sugar recovery for biobased chemical production, with additional potential applications in biofuel production and other microalgae-based industries.