design: The metagenomic library was prepared from liquid samples collected from biomethahantion bioreactors in Leipzig, Germany. The DNA was extracted from the pellet using a NucleoSpin Soil kit (ACHERY-NAGEL GmbH & Co., KG, Germany) using buffer SL2 and enhancer solution as indicated in the manufacturer's protocol, and the libraries were prepared using NEBNext Ultra II FS sample prep kit according to NEB workflow. The metagenomic library represents the genetic material of the microbial communities in the bioreactor and timepoint, providing insights into their functional potential and taxonomic composition. Samples were sequenced using Illumina NextSeq 500, generating a minimum of twenty-five million paired-end reads per sample.