Anaerobic digestion (AD) is a bioprocess widely implemented to stabilize organic waste and simultaneously produce methane - rich biogas which can be used to generate energy and heat. However, anaerobic microorganisms responsible for biological conversion of organic material into methane (CH4) are vulnerable to a wide variety of inhibitor y substances or factors which result in decreased production yields and potentially in process failure. Among them, ammonia is regularly mentioned as the primary cause of digester failure. In order to get more insights into AD microbiota inhibition by ammonia, anaerobic batch reactors performances were investigated in triplicates under ten concentrations of Total Ammonia Nitrogen (TAN) concentrations (from 0 up to 50.0 g/L) at 35∘C. Biogas production and composition as well as volatile fatty acids and ammonia concentrations were followed throughout the experiment in all the incubations. Liquid samples were collected regularly. Among them, 48 were selected to be further analyzed with different techniques: Automated Ribosomal Intergenic Spacer Analyses (ARISA) fingerprinting enabled a qualitative evaluation of the microbial dynamics; 16S rRNA gene sequencing was used to identify the key members of the microbiota, and metabolome analyses were performed by GC-MS to compare the degradation pathways in presence of various levels of inhibitor. In a first approach, principal component analyses (PCA) were computed to put forward the differences between the samples according to the ammonia concentration, and to identify the parameters explaining the differences for each methodology. Microbial community dynamics revealed that above a TAN concentration of 10.0 g/L, remarkable modifications within archaeal and bacterial communities occurred. A gradual methanogenic shift between two OTUs from genus Methanosarcina was observed 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. Similar thresholds of inhibition were highlighted based on the analysis of metabolomics data. Some molecules seem to be very specific to incubation with a high ammonia level, as benzoic acid. On the contrary, amount of hydrophenylcinnamic acid is more important in incubation with low ammonia level. As the results of individual analysis seemed highly correlated, further analyses are currently performed to integrate together the results obtained by the analytical methods so as to bring out their complementarities and communalities (Common Components and Specific Weights Analysis; CCSWA).