Research data from NCN project 2025/09/X/ST8/00634

This dataset contains experimental data from acid whey fermentation in a 15 L UASB reactor and from a separate model pertraction experiment. The Excel workbook includes metabolite concentrations measured during 86 days of UASB operation; 16S rRNA gene ASV read counts and taxonomic assignments for inoculum, reactor and acid whey samples; ITS2 ASV read counts and fungal taxonomic assignments for reactor and acid whey samples; and cumulative average fluxes of C2-C6 carboxylic acids during a 23-day model pertraction experiment. The README worksheet explains the sheet structure, sample identifiers and units. The research was funded by the National Science Centre, Poland, under the MINIATURA 9 programme (2025/09/X/ST8/00634).