Advancing Bioflocculants for Sustainable Harmful Algal Bloom Control: Mechanisms, Applications, and Resource Valorization

Harmful algal blooms (HABs) are a growing global problem that endangers ecosystems and public health and urgently needs to be controlled. The use of microbial bioflocculants for bioflocculation is an emerging technology that rapidly aggregates algal cells through charge neutralization, adsorption bridging, and other mechanisms, all while preventing cell lysis. This method achieves algae removal, effectively mitigating harmful algal blooms and enabling the recovery of potential resources. This Review comprehensively analyzes recent advances in bioflocculant technology, focusing on flocculation mechanisms, influencing factors, and applications in HAB management and algal biomass harvesting. Strategies for enhancing bioflocculant performance, including modification, composite development, and optimization of production using low-cost substrates, are discussed. The valorization of harvested algal biomass through various pathways, such as bioenergy production, fertilizer generation, and high-value compound extraction, is explored, highlighting the potential for a circular bioeconomy approach. Current challenges in bioflocculant development and application are critically examined, including the need for mechanistic understanding, efficiency improvement, and cost reduction. Future research directions emphasize elucidating flocculation mechanisms, developing hyper-productive strains, advancing modification and composite techniques, and innovating algal biomass utilization methods. This Review aims to offer a timely assessment of bioflocculant technology's current status and future prospects for sustainable HAB management and resource recovery. Its ultimate goal is to directly support ongoing initiatives in environmental protection and advance circular economy development.