Composition and functional profiling of the microbiota in the casts of Eisenia fetida during vermicomposting of brewers’ spent grains

Vermicomposting is a cost-effective biotechnology for the management of organic wastes that relies on the activity of earthworms and their associated microbiota. Here, the microbiotas of the earthworm Eisenia fetida fed with brewers’ spent grains (FBSG), cow manure (FCM) and a mix of brewers’ spent grains/cow manure (FMIX), were identified by high-throughput DNA sequencing (16S rRNA). Bacterial community variance was correlated with the pH and the organic carbon content of the rearing substrates. FBSG microbiota was enriched in Paenibacillaceae, Enterobacteriaceae, Chitinophagaceae and Comamonadaceae. In addition, FBSG microbiota had a predicted higher abundance of genes involved in cellulose degradation as well as in the nitrogen cycle and showed higher utilization of ammonia and nitrate. Results obtained will allow to optimize the vermicomposting of brewers’ spent grains and to evaluate the effect of vermicompost addition on nutrient dynamics in soil.