Four different mutants of penicillin G acylase from E. coli (PGA) were site-direct immobilized and rigidification on Eupergit C. The resulting immobilized preparations were more stable against both temperature and organic solvents than those obtained by using a more complex tailor-made disulfide-epoxy supports. The region around the position beta 380 was the most interesting one to achieve the highest PGA stabilization values (this derivative was 150-fold more stable than the corresponding soluble enzyme). Such region was further enriched in 4 additional lysine residues, and the resulting immobilized derivative was 1500-fold more stable than the same protein variant uni-punctually immobilized through position beta 380. This stabilization factor was the highest reported for PGA by immobilization on Eupergit C as commercial epoxy-acrylic immobilization carrier. (C) 2012 Elsevier Ltd. All rights reserved.