| Abstract |
Developing efficient, sustainable microalgae harvesting methods is vital to enable microalgae as renewable feedstock for food and functional nutrients. Conventional techniques face barriers in efficiency, cost, scalability, and compatibility with food processing. While extensive reviews exist on individual harvesting mechanisms, this critical review uniquely focuses on emerging, gentler technologies compatible with food-grade microalgae production, including bioflocculation, electrolytic coagulation, ultrasonic aggregation, magnetic separation and phototaxis. Novel hybrid approaches combining these mechanisms are also discussed. Focus is placed on potential advantages in separation performance, energy input, scalability and compatibility with food-grade production. Considerations for continued development like materials optimization, large-scale operation, process monitoring, and technoeconomic analysis are outlined. Bioflocculation using microbes or algal biopolymers can achieve high, selective recovery without chemicals. Electroflocculation electrolytically generates coagulants, enabling rapid, controlled destabilization and aggregation. Ultrasound/hydrodynamic cavitation disrupts cells to release coagulating organics. Magnetic nanoparticles give excellent, scalable separation under low magnetic field gradients. Phototaxis exploits directional swimming of motile species towards light. Hybrid systems integrate advantages of individual mechanisms. Continuous separation systems like electrolytic coagulation combined with flotation minimize processing steps but require holistic optimization. By avoiding toxic chemicals and reducing energy input, advanced bio-based and low-energy harvesting technologies can enhance the sustainability of microalgae production for food ingredients. This review emphasizes green technologies and their integration potential, stimulating innovation towards eco-friendly microalgae harvesting, while aligning process development with sustainable design principles. |
