Immobilized enzymes, advantageous for use in bioreactors, are difficult to decontaminate. Inactivation of microorganisms by high hydrostatic pressure could be a gentle decontamination method, provided the immobilized enzyme is stable enough. Loss in activity of α‐amylase fromBacillus subtiliscovalently bound to sepharose, after 10–30 minutes of pressure treatment at 300, 450 und 600 MPa at 50 and 70 °C and pH 8, and after 10–30 minutes of heat treatment at 50 and 70 °C and pH 8, was distinctly lower than that of equally treated non‐immobilizedB. subtilis α‐amylase with and without sepharose. At 100 MPa reaction was accelerated by 5 %.