title: The role of cellular polysaccharides in the formation and stability of aerobic granules.
abstract: OBJECTIVE
  This paper attempts to investigate the role of cellular polysaccharides in the formation and stability of aerobic granules.
  
  
  RESULTS
  Three column sequential aerobic sludge blanket reactors (R1, R2 and R3) were operated at a superficial air upflow velocity of 0.3 cm s(-1), 1.2 cm s(-1) and 2.4 cm s(-1), respectively. Aerobic granules appeared at cycle 42 in R2 and R3 with a mean size of 0.37 mm in R2 and 0.35 mm in R3, however, aerobic granulation was not observed in R1. After the formation of aerobic granules, the sludge volume index (SVI) decreased to 55 ml g(-1) in R2 and 46 ml g(-1) in R3. Aerobic granulation was concurrent with a sharp increase of cellular polysaccharides normalized to cellular proteins, which increased from 5.7 to 13.0 mg per mg proteins in R2, and 7.5-13.9 mg per mg protein in R3. The content of polysaccharides in aerobic granules was 2-3 times higher than that in the bioflocci cultivated in R1. The disappearance of aerobic granules in R2 was tightly coupled to a drop in cellular polysaccharides. After the reappearance of bioflocci in R2, the content of cellular polysaccharides were found to be restored to the level observed in R1.
  
  
  CONCLUSIONS
  It appears that the production of cellular polysaccharides could be stimulated by hydrodynamic shear force and contributes to the formation and stability of aerobic granules.
  
  
  CONCLUSIONS
  It is expected that this study would provide useful information for better understanding the mechanisms of aerobic granulation.
authors.affiliation: Environmental Engineering Research Center, School of Civil and Structural Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798.
authors.forename: J H
authors.initials: JH
authors.lastname: Tay
authors.forename: Q S
authors.initials: QS
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000332:Aerobiosis; D001422:Bacterial Adhesion; D018407:Bacterial Physiological Phenomena; D019149:Bioreactors; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*
chemical_list: D011135:Polysaccharides, Bacterial; D012722:Sewage