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Cell surface hydrophobicity and mycolic acid composition of Rhodococcus strains isolated from activated sludge foam
H M Stratton1, P R Brooks, P C Griffiths
1School of Environmental Sciences, Griffith University, Brisbane, Queensland 4111, Australia.
Summary
Bacterial hydrophobicity does not consistently correlate with foaming in activated sludge. Cell surface charge, rather than hydrophobicity or mycolic acid composition, may be key to foam stabilization in Rhodococcus strains.
Area of Science:
- Environmental microbiology
- Wastewater treatment technologies
Background:
- Foaming in activated sludge plants is a persistent operational issue.
- Bacteria in activated sludge foam are often presumed to be hydrophobic, with this trait linked to foam formation.
Purpose of the Study:
- To investigate the relationship between cell surface hydrophobicity (CSH) and foaming ability in Rhodococcus strains from activated sludge foam.
- To explore the role of mycolic acid composition and cell surface charge in bacterial foaming.
Main Methods:
- Isolation of three Rhodococcus spp. from activated sludge foam.
- Determination of CSH using microbial adherence to hydrocarbons.
- Analysis of mycolic acid chain length and unsaturation.
- Testing the efficacy of zeolite and bentonite in preventing foaming.
Main Results:
- No consistent correlation was found between CSH and foaming ability in the isolated Rhodococcus strains.
- Mycolic acid composition (chain length, unsaturation) did not correlate with CSH or foaming.
- Zeolite and bentonite effectively inhibited foaming in a pure culture of Rhodococcus sp.
Conclusions:
- Bacterial hydrophobicity and mycolic acid composition are not primary drivers of foaming in these Rhodococcus strains.
- Cell surface charge appears to be a significant factor in foam stabilization within activated sludge systems.