Trace element and temperature effects on microbial communities and links to biogas digester performance at high XXXX levels.

@entity71275 @entity3265 @entity598 @entity3794 @entity577 @entity41130 @entity3655 @entity68
BACKGROUND: High levels of @entity3265 and the presence of @entity41130 have major impacts on microbial communities and are known to cause operating problems in anaerobic degradation of protein-rich material. Operating strategies that can improve process performance in such conditions have been reported. The microbiological impacts of these are not fully understood, but their determination could help identify important factors for balanced, efficient operation. This study investigated the correlations between microbial community structure, operating parameters and digester performance in high- @entity3265 conditions. METHOD: Continuous anaerobic co-digestion of household waste and albumin was carried out in laboratory-scale digesters at high @entity3265 concentrations (0.5-0.9  g @entity3655 /L). The digesters operated for 320  days at 37 or 42    C, with or without addition of a trace element mixture including @entity68 (TE). Abundance and composition of syntrophic acetate-oxidising bacteria (SAOB) and of methanogenic and acetogenic communities were investigated throughout the study using 16S rRNA and functional gene-based molecular methods. RESULTS: Syntrophic @entity598 oxidation dominated @entity577 formation in all digesters, where a substantial enhancement in digester performance and influence on microbial community by addition of TE was shown dependent on temperature. At 37    C, TE addition supported dominance and strain @entity3794 of @entity71275 and altered the acetogenic community, whereas the same supplementation at 42    C had a low impact on microbial community structure. Both with and without TE addition operation at 42    C instead of 37    C had low impact on digester performance, but considerably restricted acetogenic and methanogenic community structure, evenness and @entity3794 . The abundance of known SAOB was higher in digesters without TE addition and in digesters operating at 42    C. No synergistic effect on digester performance or microbial community structure was observed on combining increased temperature with TE addition. CONCLUSIONS: Our identification of prominent populations related to enhanced performance within methanogenic (high dominance and @entity3794 of @entity71275 ) and acetogenic communities are valuable for continued research and engineering to improve @entity577 production in high- @entity3265 conditions. We also show that a temperature increase of only 5    C within the mesophilic range results in an extreme dominance of one or a few species within these communities, independent of TE addition. Furthermore, functional stable operation was possible despite low microbial temporal dynamics, evenness and @entity3794 at the higher temperature.
