Desalination 148 (2002) 187–191 Presented at the International Congress on Membranes and Membrane Processes (ICOM), Toulouse, France, July 7–12, 2002. 0011-9164/02/$– See front matter © 2002 Elsevier Science B.V. All rights reserved *Corresponding author. Biopolymer purification by ultrafiltration J. Jorda, P. Marechal, L. Rigal, P.-Y. Pontalier* Laboratoire de chimie Agro-industrielle (LCA-CATAR), 118, route de Narbonne, F31077 Toulouse cedex 4, France Tel. +33 (5) 62885719; Fax +33 (5) 62885730; emails: jjorda@ensct.fr, pmarechal@ensct.fr, lrigal@ensct.fr, pont@ensct.fr Received 8 February 2002; accepted 11 March 2002 Abstract 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 (kD). 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 . Keywords: Ultrafiltration; Biopolymer; Concentration; Polarization; Fouling; Viscosity 1. Introduction The technological properties (emulsifier, thickener, gelling, film forming, coating agent) of biopolymers make them attractive for many industrial applications [1]. Among these polymers arabinoxylans and rhamnogalacturonan are polymers extracted from crops products. Extraction stage has to disrupt cell walls, using mechanic and chemical forces, which therefore leads to complex solutions. Purification of such solutions is rather difficult with many steps combining, depending on the polymer, centri- fugation, filtration and alcoholic precipitation [2– 3]. Precipitation is very expensive because extrac- tion lead to very dilute solutions and precipitation needs several volume of alcohol for one volume of solution. Ultrafiltration could be included for purification and concentration before spray drying [2,4]. Ultrafiltration is a very attractive technique for the concentration of sensitive solution because it can be used at room temperature. The MWCO of the membrane are usually about 10–20 kDa [5], even some authors used 300 kDa [6] or 3 kDa membranes [4]. Optimal conditions are not easily