Abstract
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 (Rb) received bioaugmentation dosage for a certain period (d100-d170) and stopped afterward (d170-d220), while the same applied to the control (Rc) 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 (Rb: 0.917–1.081; Rc: 0.551–0.677). Moreover, bioaugmentation brought Rb 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.
Highlights
Anaerobic digestion (AD) acts as a viable technology to extract the residual value of agricultural wastes generated by farm sectors
Proteins related to carbohydrate metabolism, amino acid metabolism, energy metabolism, and cofactors and vitamin metabolism were predominant. The predominance of these metabolisms was due to the characteristic of cow manure (CM) since carbohydrate and crude proteins are significant components in CM
Extensive modification of indigenous microbial guilds was observed when bioaugmentation was conducted in a continuous process treating CM
Summary
Anaerobic digestion (AD) acts as a viable technology to extract the residual value of agricultural wastes (i.e., crop residues and manure) generated by farm sectors Within these criteria, researchers have exploited many attempts to improve the degradation of lignocellulosic components within agricultural wastes due to their recalcitrance in hydrolysis in AD. To mimic the real application strategies in industrial AD installation, one should seek loneterm continuous/semi-continuous experiments to justify the feasibility of injected bioaugmentation dosage Under such circumstances, the introduced pure culture competes with the indigenous microbes to metabolize organic matter of CM and face the wash-out stress induced by the daily fed-and-withdraw mode adopted in most running AD plants. Such improvement could partially sustain, reflected by an 11% higher daily methane yield in the bioaugmented reactor compared with the control when bioaugmentation stopped (Table 1)
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