Implementing metatranscriptomics to unveil the mechanism of bioaugmentation adopted in a continuous anaerobic process treating cow manure.

This study aimed to investigate the effect of bioaugmentation on microbial community and function in a continuous anaerobic process treating lignocellulosic cow manure. One reactor (R) received bioaugmentation dosage for a certain period (d100-d170) and stopped afterward (d170-d220), while the same applied to the control (R) except sterilized bioaugmentation dosage was introduced. Samples were taken on day130, 170 and 220 from both reactors for metatranscriptomic analysis. The results underlined the promotive effect of bioaugmentation on indigenous microorganisms regarding hydrolysis and methanogenesis. Bioaugmentation contributed to the enrichment of Clostridium, Cellvibrio, Cellulomonas, Bacillus, Fibrobacter, resulting in enhanced cellulase activity (R: 0.917-1.081; R: 0.551-0.677). Moreover, bioaugmentation brought R the prosperity of uncultured_ Bathyarchaeia, a prominent archaeal group responsible for the improved methyl-coenzyme M reductase activity, thus accelerated methanogenesis. Unique metabolic pathways (autotrophic carbon fixation and methanogenesis) in uncultured_ Bathyarchaeia broadened the horizon of its fundamental role as acetogens and methanogens in anaerobic digestion.