Chapter 5 focuses on the elaboration of microbial flocculants. First, classify the microbial flocculants, and then delve into their flocculation mechanisms, such as the flocculation mechanism of MBF, as well as the related factors affecting the flocculation effect and the measurement indicators of the flocculation effect. In terms of preparation and production, the key links such as the isolation and screening of MBF-producing bacteria, strain identification, optimization of the fermentation process, extraction and purification of MBF were introduced. Subsequently, the application of microbial flocculants in water environmental protection is explained, covering areas such as raw water purification, sewage treatment, sludge conditioning, and microalgae collection. Finally, let's look forward to its development trends, including the research and development of MBF-producing bacteria with strong applicability, the development of green and low-cost alternative culture media, the improvement of intelligent regulation methods for MBF production, the strengthening of flocculation enhancement in MBF compounding and combination, as well as the promotion of MBF configuration, safety assessment and application research, etc.