Coexistence of sulfate-reducing and methane-producing populations in upflow anaerobic sludge bed reactor treating lignocellulosic effluent with material balance

Microbial shift and predominance profile of a mesophilic upflow anaerobic sludge bed (UASB) reactor treating lignocellulose-rich wastewater [i.e., paper industry effluent with 665 mg SO₄⁻²/L and COD/SO₄ = 2–8] was investigated using next-generation sequencing (NGS) technology in accordance with a mass balance determination on sulfur and organic compounds. Since paper producing industries generate wastewaters with high organic and sulfate concentrations, coexistence of microbial-especially of sulfur-reducing and methane-producing-communities and their interactions have been also searched out considering the impact on biogas yield (~ 0.16 L CH₄/g COD_removed) and sulfate reduction (up to 82%). Analysis of the microbiomes by Illumina sequencing showed that Desulfovibrio spp. were the detected sulfate-reducing bacteria (SRB) coexisting with methane-producing archaea (MPA). Despite no evident inhibition of relatively high sulfate on biogas generation, predominance of Euryarchaeota decreased by nearly half and taxonomic classification revealed a shift of microbial population from aceticlastic (Methanosaeta) to hydrogenotrophic (Methanolinea) methanogens as operation continued probably due to their general tendency to dominate in stressed condition. Bacteroidetes, Firmicutes, and Proteobacteria (involving major SRB genera in the delta subclass) phyla had the highest ratios of relative abundances demonstrating the crucial role of their coexistence during the removal of the pollutants in lignocellulosic wastewaters. Graphical abstract: [Figure not available: see fulltext.]