Influence of inoculum on process parameters and microbial communities during anaerobic digestion of cattle manure: Insights from metabarcoding analysis

Linking the variety of microbial ecology attributes to system functioning is critical to improve operational strategies and to support microbial pathways, in order to conceive efficient and reliable anaerobic digestion process. In the present study, we conducted a direct comparison between two digesters regarding the process parameters and microbial community dynamics between two digesters: one containing only the substrate (cattle manure) (Digester S), and the other (Digester F) enriched with an inoculum. This study aimed to investigate taxonomic and functional changes in the digester microbiome using a 16S rRNA sequencing approach. Results exhibit that the bacterial richness, diversity, and regularity were higher in Digester F. This later showed also a higher biogas yields (BY) and the process performance indicators compared to Digester S. The BY obtained in digester F was 2.17 times higher than that obtained in digester S. Furthermore, significant correlations were obtained between biogas yields (BY) and microbial communities with Firmicutes/Bacillota (Clostridium, Enterococcus, Streptococcus, Ruminococcaceae, Mogibacterium, and Turicibacter), Actinobacteria (Corynebacterium), and Bacteroidetes (Bacteroides, Paludibacter) in the AD systems. Conversely, in Digester S, biogas yield (BY) was highly significant and positively correlated with the abundance of Actinobacteria (Rhodococcus) and Proteobacteria (Moraxella, Oxalobacter). Moreover, the inoculum in digester F resulted in the enrichment of main bacterial functions involved in biogas production. This study provides results that justify the changes in the structure of the microbial community and the functional strategy used by the most representative micro-organisms in the consortia that carried out this process.