Structure of a cellulose degrading bacterial community during anaerobic digestion

Abstract

It is widely accepted that cellulose is the rate-limiting substrate in the anaerobic digestion of organic solid wastes and that cellulose solubilisation is largely mediated by surface attached bacteria. However, little is known about the identity or the ecophysiology of cellulolytic microorganisms from landfills and anaerobic digesters. The aim of this study was to investigate an enriched cellulolytic microbial community from an anaerobic batch reactor. Chemical oxygen demand balancing was used to calculate the cellulose solubilisation rate and the degree of cellulose solubilisation. Fluorescence in situ hybridisation (FISH) was used to assess the relative abundance and physical location of three groups of bacteria belonging to the Clostridium lineage of the Firmicutes that have been implicated as the dominant cellulose degraders in this system. Quantitation of the relative abundance using FISH showed that there were changes in the microbial community structure throughout the digestion. However, comparison of these results to the process data reveals that these changes had no impact on the cellulose solubilisation in the reactor. The rate of cellulose solubilisation was approximately stable for much of the digestion despite changes in the cellulolytic population. The solubilisation rate appears to be most strongly affected by the rate of surface area colonisation and the biofilm architecture with the accepted model of first order kinetics due to surface area limitation applying only when the cellulose particles are fully covered with a thin layer of cells.

Straw- and slurry-associated prokaryotic communities differ during co-fermentation of straw and swine manure

“…However, few studies have uncovered the tightly substrate-attached microbiota and their correlations with fermentation performance. The dynamics of substrate-attached Clostridium observed by fluorescence in situ hybridization indicated its dominant role in substrate solubilization in anaerobic digesters (O'Sullivan et al 2005;Syutsubo et al 2005). In the co-fermentation system, spatial distribution of microbiota with different function may aid microbial communities for substrate competition and responses to the changes in physicochemical conditions during fermentation process.…”

Microbial community structure in anaerobic co-digestion of grass silage and cow manure in a laboratory continuously stirred tank reactor

“…Therefore, information on the microbial ecology and mechanisms of hydrolysis during anaerobic digestion is of importance in seeking to increase the rate of hydrolysis and the overall efficiency of the anaerobic digestion process. A number of bacteria well known for their cellulolytic capabilities, and mostly belonging to the order Clostridiales, have been studied (Burrell et al 2004;Chachkhiani et al 2004;Lynd et al 2002;O'Sullivan et al 2005). However, the investigation of microbial community structure taking part in the anaerobic co-digestion of crops and animal manure continue to be lacking.…”

Extremophiles in biofuel synthesis

“…The third and final step is known as methanogenesis, performed by slow-growing, fastidious archaea, yielding up to 70% CH 4 and CO 2 , NH 3 and H 2 S as by-products [4]. The exact microbial communities involved in each of the three steps is variably dependent on the process (mesophilic or thermophilic) as well as the type of substrate and fermenter employed [51][52][53][54]. In large-scale industrial biogas plants, the two-stage process is gaining preference, separated into hydrolysis and methanogenesis/ acetogenesis, which allows for the optimization of each process individually (pH and temperature).…”