Influence of co-substrates on structure of microbial aggregates in long-chain fatty acid-fed anaerobic digesters.
OBJECTIVE
The purpose of this study was to investigate the influence of co-substrates, such as glucose and cysteine, on the structure of microbial aggregates in anaerobic digesters treating oleate, a long-chain fatty acid (LCFA).


RESULTS
Transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) were used to examine the structure of microbial aggregates. Fluorescence in situ hybridization (FISH) techniques were also used to characterize and localize the different trophic groups present in the aggregates. Oleate was found to inhibit the methanogenic activity and formation of granular biomass in digesters. The addition of co-substrates, such as glucose and cysteine either singly or in combination, increased the methanogenic activity and formation of granular biomass. Glucose was more effective than cysteine in reducing the inhibition by oleate on the methanogenic bacteria and in enhancing the formation of granules.


CONCLUSIONS
The addition of nutrient substrate, such as glucose and cysteine could decrease the toxicity of LCFA on anaerobic granulation.


CONCLUSIONS
The results suggest that the addition of other substrates might decrease the toxicity of LCFA on the granulation of biomass in anaerobic digesters and enhance methanogenic activity. A combination of TEM, CLSM and FISH techniques provides a better tool for visualizing microbial aggregates and for differentiating and localizing different microbial groups within these aggregates.
Centre for Organic Waste Management, Murdoch University, Perth, WA, Australia. kuang@essun1.murdoch.edu.au
Y
Y
Kuang
M
M
Lepesteur
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P
Pullammanappallil
G E
GE
Ho
D001105:Archaea / Q000254:growth & development* / Q000378:metabolism; D001421:Bacteria, Anaerobic / Q000254:growth & development* / Q000378:metabolism; D019149:Bioreactors; D003545:Cysteine / Q000378:metabolism; D017753:Ecosystem; D019605:Euryarchaeota / Q000254:growth & development* / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D008697:Methane / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D019301:Oleic Acid / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D014865:Waste Disposal, Fluid
D005231:Fatty Acids, Unsaturated; D019301:Oleic Acid; D005947:Glucose; D003545:Cysteine; D008697:Methane; D010100:Oxygen