Prokaryotic population dynamics and interactions in an AnSBBR using tequila vinasses as substrate in co-digestion with acid hydrolysates of Agave tequilana var. azul bagasse for hydrogen production

Aims The purpose of this study was to characterize the prokaryotic community and putative microbial interactions between H-2-producing bacteria (HPB) and non-HPB using two anaerobic sequencing batch biofilm reactors (AnSBBRs) fed with tequila vinasses in co-digestion with acid hydrolysates of Agave tequilana var. azul bagasse (ATAB). Methods and Results Two AnSBBRs were operated for H-2 production to correlate changes in physicochemical and biological variables by principal component analysis (PCA). Results indicated that H-2 yield was supported by Ethanoligenens harbinense and Clostridium tyrobutyricum through the PFOR pathway. However, only E. harbinense was able to compete for sugars against non-HPB. Competitive exclusion associated with competition for sugars, depletion of essential trace elements, bacteriocin production and resistance to inhibitory compounds could be carried out by non-HPB, increasing their relative abundances during the dark fermentation (DF) process. Conclusions The global scenario obtained by PCA correlated the decrease in H-2 production with the lactate:acetate molar ratio in the influent. At the beginning of co-digestion, this ratio had the minimum value considered for a net gain of ATP. This fact could cause the reduction of the relative abundance of C. tyrobutyricum. Significance and Impact of the Study This is the first study that demonstrated the feasibility of H-2 production by Clostridiales from acid hydrolysates of ATAB in co-digestion with tequila vinasses.