Isolation of acetic, propionic and butyric acid-forming bacteria from biogas plants.

•Data about bacteria involved in formation of acetic, propionic and butyric acid in BGP.•New and known species of acid-forming bacteria were isolated from BGPs.•Physiological features of the isolates are described.•The role of the isolates in the degradation process is discussed.•Design of specific primer sets for quantification of acid-forming bacteria in BGPs