Anaerobic digestion of biowaste under extreme ammonia concentration: Identification of key microbial phylotypes

Ammonia inhibition represents a major operational issue for anaerobic digestion (AD). In order to get more insights into AD microbiota resistance, anaerobic batch reactors performances were investigated under a wide range of Total Ammonia Nitrogen (TAN) concentrations up to 50.0 g/L at 35 °C. The half maximal inhibitory concentration (IC₅₀) value was determined to be 19.0 g/L. Microbial community dynamics revealed that above a TAN concentration of 10.0 g/L, remarkable modifications within archaeal and bacterial communities occurred. 16S rRNA gene sequencing analysis showed a gradual methanogenic shift between two OTUs from genus Methanosarcina when TAN concentration increased up to 25.0 g/L. Proportion of potential syntrophic microorganisms such as Methanoculleus and Treponema progressively raised with increasing TAN up to 10.0 and 25.0 g/L respectively, while Syntrophomonas and Ruminococcus groups declined. In 25.0 g/L assays, Caldicoprobacter were dominant. This study highlights the emergence of AD key phylotypes at extreme ammonia concentrations.