MEMBRANE SURFACE MODIFICATION BY PLASMA POLYMERIZATION OF ETHYLENEDIAMINE FOR FRACTINATION OF SACCHARIDES Haci Ali Gulec 1 , Arzu Topacli 2 , Cafer Topacli 2 , Yasin Sen 3 , Nedim Albayrak 1 , Mehmet Mutlu 3 1 Department of Food Engineering, Yuzuncu Yil University, 65080 Van, Turkey. 2 Department of Physical Engineering, Hacettepe University, 06800 Ankara, Turkey 3 Department of Food Engineering, Hacettepe University, 06800 Ankara, Turkey ABSTRACT: Cellulose acetate ultrafiltration membranes (CAs) were modified by plasma polymerization (PP) of ethylenediamine (EDA) to prepare extremely hydrophilic nanofiltration membranes. Low-Frequency (LF) and Radio-Frequency (RF) excitations were used for this purpose. The contact angle results showed that the grafted amino groups caused great increase on the polar nature of the CAs studied. The best treatment results were obtained at 120 W and 10 min. for LF-modified CAs and 80 W and 30 min. for RF- modified CAs. A complete and permanent hydrophilic modification of a CA is achieved by LF plasma treatment while polymer layer deposited by RF plasma was not as stable as expected. Therefore, only LF-modified CAs were characterized in details by Fourier Transform InfraRed (FTIR) spectroscopy with Horizontal Attenuated Total Reflection (HATR) attachment and Scanning Electron Microscopy (SEM). This study illustrates the importance of selecting the right plasma system and parameters for cellulose acetate ultrafiltration membranes to become extremely hydrophilic for better separation properties. KEYWORDS: membrane, separation, oligosaccharide production, plasma polymerization, bioreactor systems 1. Introduction Galactooligosaccharide (GOS) formation is a kinetically controlled transgalactosylation reaction of β-galactosidase enzyme [1]. The same enzyme also catalyzes the hydrolysis of lactose to glucose and galactose, which not only reduces the GOS yield but also inhibits the enzyme reaction. Therefore, it is desirable to remove glucose and galactose from the reaction medium to promote the GOS yield and formation rate and to provide high product purity [2]. It was anticipated that by continuously removing these monosachharides (MSs) from the reaction media via membrane seperation without lactose removal, both GOS formation rate and yield from lactose can be enhanced. In this scope, it is crucial to design a novel membrane to separate MSs from enzymatic reaction mixture selectively since commercially avaliable membranes were not efficient for removal MSs from di- and OSs [3]. Plasma modification has become an alternative technique to wet-chemical surface modifying treatments due to its many important advantages such as uniformity and reproducibility, short reaction time and environmental safety [4]. Plasma polymerization has been extensively studied to modify the surface of polymeric membranes for enhancement of permeability, selectivity and fouling resistance [5]. In this study, it was attempted to modify commercial cellulose acetate (CA) asymmetric membranes via RF- and LF-type low-pressure PP coating of EDA in order to enhance its pore size and separation properties via activating its surface. We choosed commercially available cellulosic membrane with asymmetric pore distribution as a substrate material because it is frequently used for UF [6] and reverse osmosis (RO) [7] processes in food industry. Firstly, PP conditions – plasma system, plasma power, and exposure time– were optimized by measuring the surface free energy (SFE) and chemical resistance of plasma polymer coatings. Chemical resistance of polymeric EDA layer deposited on membrane surface was tested by evaluation of interfacial free energy between membrane and deionized water before and after membrane/aqueous solution interaction. The chemical resistances of EDA layers deposited by LF- and RF-plasma systems were compared. After optimization procedure, only LF-modified CAs supplying more stable polymer films were characterized by FTIR-HATR spectrometer and more detailed chemical analysis were performed.