16S rRNA gene based analysis of the microbial diversity and hydrogen production in three mixed anaerobic cultures

To explore of role of microbial diversity and its functionality in commercial bioreactors, three anaerobic microbial communities from Ontario, Canada were characterized using 16S rRNA gene-based, clone library sequencing and terminal restriction fragment length polymorphism (T-RFLP) and compared with the hydrogen (H₂) and methane yields. The T-RFLP method showed more operational taxonomic units than the clone library sequence analysis; however, the two methods showed similar dominant species and relative diversity while Spearman's Rank correlation coefficient (r) values ranged from 0.82 to 0.91. The Chao 1 and Shannon-Wiener indices revealed that the cultures samples have highly diverse microbial communities. Comparatively, cultures from a municipal wastewater treatment plant (CA) showed more diversity than those from facilities treating effluents from a baby food processor and a brewery. Even though culture CA has the highest microbial diversity, low H₂ and methane production yield was attributed to the presence of sulphate reducers, propionate producers and a low percentage of methanogens. This study confirms that the selection of the source of mixed anaerobic cultures plays an important role in H₂ and methane production.