Fluorescent Probe Enable Visual Quantification the Quantitative Relationship of Surface Hydrophobic Properties of Microthrix Parvicella.

To achieve visualized, dynamic quantitative monitoring of Microthrix parvicella surface hydrophobicity during activated sludge filamentous bulking and to overcome the limitations of traditional methods in accurately characterizing filamentous bacteria hydrophobicity, seven fluorescent probes with distinct polarities were designed and synthesized based on the specific binding mechanism between lipid substrates and lipase. Results showed probe dipole moment and binding energy are key factors affecting staining efficiency. Probes with small dipole moments (< 10 Debye) and high binding energies (<-9.0 kcal/mol) stably bind to nonpolar regions of the cell membrane and lipase, maintaining staining ability but exhibiting low sensitivity to hydrophobicity changes. Probes with large dipole moments (> 20 Debye) and low binding energies (>-9.0 kcal/mol) were sensitive but lost staining ability rapidly as hydrophobicity decreased. Moderate-parameter probes exhibit a balance between stability and sensitivity, with fluorescence intensity consistent with M. parvicella growth cycle and Sludge Volume Index (SVI), thereby accurately reflecting hydrophobicity fluctuations during bulking.