Low-fouling ultrafiltration membranes have been prepared by simultaneous photograft copolymerization of poly(ethylene glycol) methacrylate (PEGMA) onto a polyethersulfone (PES) membrane with a nominal cut-off of 50 kg/mol. A comprehensive characterization was performed by flux measurement and sieving curve analysis, FTIR-ATR spectroscopy, contact angle and zeta potential measurement. The effects of UV irradiation and monomer concentration on membrane characteristics as well as membrane performance were also described. Model solutions of sugarcane juice polysaccharides and the protein BSA were used to examine the membrane performance. The results showed that UV irradiation time was the most important parameter with monomer concentration as another parameter to adjust the degree of functionalization. All modified membranes showed more resistance to fouling and higher rejection than unmodified membrane for both model solutions. A reduction of permeability due to pore constriction or even blocking by grafted polyPEGMA was also observed. Surface functionalization of PES UF membranes using relatively high monomer concentration (40 g/L) at medium irradiation times (1.5-3 min) was recommended as the best condition with respect to flux, rejection and fouling. This study provides valuable information for the development of low-fouling ultratiltration membranes especially for sugarcane juice clarification. (c) 2006 Elsevier B.V. All rights reserved.