Production and characterization of efficient bioflocculant in high-turbidity drinking water treatment: Identification of flocculation-related genes

Bioflocculants are eco-friendly water treatment agents produced by bioflocculant-producing strains that are valuable in drinking water turbidity removal. The major challenges in the application of bioflocculants include low flocculation efficiency, high production costs, and unclear flocculation-related genes. In this study, Pseudomonas sp. ZC-41 a highly efficient bioflocculant-producing strain, was isolated from activated sludge to produce polysaccharide-based bioflocculant MBF-ZC with 94.12% flocculation efficiency under more economical culture conditions, which can solve the problem of low flocculation efficiency. Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed MBF-ZC contained hydroxyl, carboxyl, and amine groups, crucial for flocculation via adsorption bridging effects as the main flocculation mechanism. The 2393 differentially expressed genes (DEGs) in the transcriptome of strain ZC-41 were classified into five co-expression modules, and the turquoise module was associated with flocculation efficiency and bioflocculant yield. Nineteen flocculation-related genes were identified by combining functional pathways related to sugars. In addition, response surface methodology was optimized to achieve the efficiency of 93.57% for turbidity removal from high-turbidity water by bioflocculant. The results not only provide a solid theoretical foundation to solve the challenges of bioflocculants, but also enrich strategies for high-turbidity drinking water treatment.