ABSTRACT
This chapter looks at the role of cell surface hydrophobicity in the formation of aerobic granular sludge in a sequencing batch reactor. For water-soluble protein, the majority of its hydrophilic amino acids presents at the water interface, whereas the more hydrophobic amino acids are located inside the three-dimensional framework of the macromolecule. In contrast with protein that comprises hydrophilic and/or hydrophobic amino acids, polysaccharides are made up of different sugars that are hydrophilic and soluble in water. There are a number of methods available to characterize the cell surface hydrophobicity, including contact angle measurement, bacterial adherence to hydrocarbons, hydrophobic interaction chromatography, salting out aggregation, adhesion to solid surfaces, and binding of fatty acids to bacterial cells. The chapter shows that cell surface hydrophobicity is an essential triggering force of cell-to-cell aggregation that is a crucial initial step towards microbial granulation, and can further strengthen the aggregated microbial structure.
