The invention disclose a method for purifying microbial protease, comprising:(i) providing an aqueous liquid sample containing a microbial protease, and a separation medium comprising a base matrix and a plurality of attached ligands that are capable of binding to microbial protease;(ii) contacting separation medium with the sample under conditions permitting binding of microbial protease to the separation medium; and (iii) desorbing microbial protease from the separation medium, wherein the base matrix is hydrophilic and the plurality of ligands are hydrocarbon groups in which all carbon atoms are sp3-hybridised.