Microbial adaptation to high ammonia concentrations during anaerobic digestion of manure-based feedstock: biomethanation and 16S rRNA gene sequencing

BACKGROUND: Microbial consortia resistant to high ammonia concentrations may facilitate biogas production from high ammonia-containing wastes and manures during anaerobic digestion. Microbial communities were gradually enriched via sequential batch cultivations (stepwise exposure) at increasing ammonia concentrations up to the extremely high concentration of 9 g total ammonia nitrogen (TAN) L−1. This study examined the adaptation of anaerobic microbial consortia to high ammonia concentrations by the use of a complex substrate based on manure in order to generate tailor-made inocula for bioaugmentation purposes. RNA analysis was performed to determine the microbial community composition and activity of anaerobic bacteria and methanogens. RESULTS: The enrichment series was successful in terms of methane production at ammonia concentrations as high as 5 g TAN L−1 in comparison with the control concentration of 2 g TAN L−1. Methanosarcina was the core active dominant methanogen genus in all enrichment cultures and its relative activity was sharply increased at 3 g and 9 g TAN L−1. Cellulolytic bacteria activity mostly decreased with ammonia increase. Moreover, syntrophic butyrate and long-chain fatty acid degraders along with hydrogenotrophic methanogens were activated at increased ammonia concentrations. CONCLUSIONS: The results of the study demonstrated an efficient method to enrich ammonia-tolerant microbial consortia for bioaugmentation purposes in biogas reactors with concentrations ≤5 g TAN L−1. RNA analysis revealed high relative abundances of Methanosarcina and hydrogenotrophic methanogens at high concentrations of ammonia. © 2020 Society of Chemical Industry. © 2020 Society of Chemical Industr