Ultrafiltration has been investigated for the concentration of diluted biopolymer solutions. Trials were realized with membranes of different molecular weight cut off (MWCO) and configuration modules. Results indicates that hollow fiber module gives the best results with the membrane of 6 kilodalton (W). Arabinoxylan solutions were concentrated with a ratio of 2.4 and a final permeate flux of 14.5 L/h.m(2). Rhamnogalacturonan solutions were concentrated with a ratio of 5 and a final permeate flux of 25 L/h.m(2).