Desalination 200 (2006) 507–508 Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved. Utilisation of a membrane bioreactor for pectin hydrolysis by Aspergillus niger polygalacturonase Katalin Bélafi-Bakó a *, Matild Eszterle b , Katalin Kiss a , Nándor Nemestóthy a , Sándor Kovács a , László Gubicza a a Research Institute of Chemical and Process Engineering, University of Veszprém, Egyetem u. 10., 8200 Veszprém email: bako@mukki.richem.hu b Research Institute of Hungarian Sugar Industry, Tolnai L. u. 25., 1084 Budapest, Hungary Received 22 October 2005; accepted 4 March 2006 1. Introduction In the fruit-processing industry it is very important to use pectolytic enzymes [1,2] to increase yields, improve liquefaction and clarifi- cation. Complete hydrolysis of pectin results in D-galacturonic acid (monomer of pectin mole- cules) which is an important acidifying agent in food industry. Polygalacturonase enzymes belong to the group of depolymerising hydrolytic pecti- nases, and they are able to hydrolyse pectin and/ or pectic acid. Kulbe et al. have assumed that PG enzyme was inhibited by its monomer [3], therefore membrane bioreactors seem a promis- ing reactor type to realise the enzymatic reaction, since membrane can retain the large molecules, while small inhibitory compounds easily pass through it [4,5]. Membrane bioreactors have already been successfully applied for enzymatic polysaccharide hydrolysis in our laboratory [6–8]. Now the aim was to use a flat sheet type mem- brane bioreactor to study enzymatic hydrolysis of pectin. 2. Experimental Pectin substrate (low esterification degree, LM-5CS) was received as a gift from Polding Ltd. (Budapest, Hungary). Polygalacturonase enzyme (PG) from Aspergillus niger was pur- chased from Sigma (USA), its activity was 1.7 U/mg. To study the kinetics of the reaction, shaking flask experiments were carried out in a New Brunswick Scientific (USA) shaking incubator. Citrate buffer was used (pH = 4.1) to prepare the substrate solutions with various concentrations, and the operational conditions of the experi- ments were 50 o C and 150 rpm. To determine the product inhibition, galacturonic acid (product) was added initially to some of the substrate solutions. Experiments were conducted in a membrane bioreactor, as well. Diluted substrate solution (citrate buffer, pH 4.1) containing the enzyme was circulated from a stirred thermostated vessel through a flat sheet membrane module (thermostated). The material of the ultrafiltra- tion membrane was regenerated cellulose, cut off 30 kDa. *Corresponding author. doi:10.1016/j.desal.2006.03.414