Abstract: A process is disclosed for preparing aqueous phytase-containing liquids involving culturing microorganisms of the genus Aspergillus or Trichoderma in a medium containing assimilable carbon and nitrogen sources (e.g., glucose and ammonium ions), filtering the medium, and subjecting the resulting filtrate to ultra-filtration to give an aqueous composition having at least 14,000 FTU/g. This aqueous liquid optimally can be used to prepare granulates that can be incorporated in animal feedstuffs.