Isolation and characterization of a strain with high microbial attachment in aerobic granular sludge

Aerobic granule is a special microbial aggregate associated with biofilm structure.The formation of aerobic granular sludge is primarily depending on its bacterial community and relevant microbiological properties.In this experiment,a strain with high microbial attachment was isolated from aerobic granular sludge,and the detailed characteristics were examined.Its high attachment ability could reach 2.34(OD600 nm),while other low attachment values were only around 0.06-0.32,which indicated a big variation among the different bacteria.The strain exhibited a very special morphology with many fibric fingers under SEM observation.A distinctive behaviour was to form a spherical particle by themselves,which would be very beneficial for the formation and development of granular sludge.The EPS measurement showed that its PN content was higher than low attachment bacteria,and 3 DEEM confirmed that there were some different components.Based on the 16 S rRNA analysis,it was identified to mostly belong to Stenotrophomonas.Its augmentation to particle sludge cultivation demonstrated that the strain could significantly promote the formation of aerobic granule.Conclusively,it was strongly suggested that it might be used as a good and potential model strain or chassis organism for the aerobic granular sludge formation and development.

The biological effect of metal ions on the granulation of aerobic granular activated sludge

As a special biofilm structure,microbial attachment is believed to play an important role in the granulation of aerobic granular activated sludge（AGAS）.This experiment was to investigate the biological effect of Ca^2＋,Mg^2＋,Cu^2＋,Fe^2＋,Zn^2＋,and K＋which are the most common ions present in biological wastewater treatment systems,on the microbial attachment of AGAS and flocculent activated sludge（FAS）,from which AGAS is always derived,in order to provide a new strategy for the rapid cultivation and stability control of AGAS.The result showed that attachment biomass of AGAS was about 300%higher than that of FAS without the addition of metal ions.Different metal ions had different effects on the process of microbial attachment.FAS and AGAS reacted differently to the metal ions as well,and in fact,AGAS was more sensitive to the metal ions.Specifically,Ca^2＋,Mg^2＋,and K＋could increase the microbial attachment ability of both AGAS and FAS under appropriate concentrations,Cu^2＋,Fe^2＋,and Zn^2＋were also beneficial to the microbial attachment of FAS at low concentrations,but Cu^2＋,Fe^2＋,and Zn^2＋greatly inhibited the attachment process of AGAS even at extremely low concentrations.In addition,the acylated homoserine lactone（AHL）-based quorum sensing system,the content of extracellular polymeric substances and the relative hydrophobicity of the sludges were greatly influenced by metal ions.As all these parameters had close relationships with the microbial attachment process,the microbial attachment may be affected by changes of these parameters.