Microbial community structure
During the intial granulation process 16S rRNA showed that the mixed microbial community was dominated by Clostridium pasteurianum . When the SRT was prolonged to 50 d the microbial community shifted to a community dominated (>50% operational taxonomic unit (OTU) based) by Bifidobacterium scardovii . Additionally,Propionibacterium thoenii and Megasphaera cerevisiae were detected and contributed for 20-30% in total to the community structure based upon 16S rRNA. This community structure remained similar at an SRT of 10-20 d. While decreasing the SRT to 1-2 d a more diverse community structure consisting of 4 species, next to the aforementioned species the 4th observed species wasSaccharibacteria . Once the enrichment matured, again B. scardovii was the dominant microorganism (>65% OTU based).

Discussion