Micro-nanobubble technology in microalgae cultivation: a comprehensive overview

Microalgae cultivation is currently constrained by two major techno-economic bottlenecks: poor gas-liquid mass transfer and high harvesting costs. This review examines micro-nanobubble (MNB) technology as a strategic solution to address these barriers. Owing to characteristics such as high internal pressure, prolonged residence time, and colloidal stability, MNBs significantly enhance the volumetric mass transfer coefficient ( ) while minimizing hydrodynamic shear stress. Case studies demonstrate that MNBs not only increase biomass productivity but also facilitate efficient flotation-based harvesting with low energy consumption (below 0.5 kWh·kg⁻¹ of dry biomass), while simultaneously improving nutrient removal in wastewater. Despite remaining challenges in scaling up, this technology offers a promising pathway for integration into circular economy models, driving the commercialization of microalgae for biofuels and high-value products.