We here report on the performance of poly(ethersulfone) membranes modified with 4-hydroxybenzoic acid and gallic acid as substrates, and using laccase as biocatalyst under several modification conditions. The average flux of the base membrane was never reduced more than 20% (mostly below 10% reduction) by modification with 4-hydroxybenzoic acid, and not more than 9% for gallic acid. The mechanical and thermal properties of the membrane were not adversely affected by the modification method. For 4-hydroxybenzoic acid, longer modification times (i.e., hours) and higher substrate concentrations lead to modified membranes with a better protein repellence. The reaction with gallic acid is faster, but less effective in terms of the resulting protein repellence. In conclusion, the laccase-catalyzed modification of poly(ethersulfone) membranes is a mild method with low environmental impact that leads to effective protein repellence while keeping the bulk properties of the base membrane intact. This makes laccase-catalyzed modification an interesting alternative for currently used membrane modification methods. (C) 2011 Elsevier B.V. All rights reserved.