Interspecies microbial nexus facilitated methanation of polysaccharidic wastes

[Display omitted] •Addition of polysaccharidic wastes in digesters enhanced the methane yield by 75%.•Prevotella, Eubacterium, and Lachnoclostridium were major saccharolytic bacteria.•Dominance of Methanosaeta suggests acetoclastic methanogenesis as prevalent pathway.•Acetoclastic methanogens showed associations with propionate oxidizers. Compositional variations in organic wastes influence microbial abundancy and syntrophy during anaerobic digestion (AD), impacting the normal performance of digesters for methanation. Investigation of the microbial dynamics during AD following augmentation with polysaccharidic wastes (PW) revealed the association of effective digester performance and methane yields with the microbial nexus. Dominance of the acidogenic saccharolytic genera, Prevotella, Eubacterium, and Lachnoclostridium, enhanced the utilization of carbohydrates (54%) in PW-augmented digesters. Spearman’s rs correlation showed dynamic interspecies interactions among acetogenic syntrophs, and that of iron oxidizers/reducers with acetoclastic and hydrogenotrophic methanogens. Propionate oxidizers in Chloroflexi (i.e., Bellilinea, Levilinea, and Longilinea) exhibited positive associations with acetoclastic methanogens. Increase in the population of acetoclastic methanogens (Methanosaeta, 77% and Methanosarcina, 9%) accelerated the methanogenic activity of PW-augmented digesters by 7 times during the exponential phase, increasing the methane yield (75%) compared to the control. Thus, microbial syntrophy facilitated the effective methanation of PW during AD process.