Effect of membranes with various hydrophobic/hydrophilic properties on lipase immobilized activity and stability Guan-Jie Chen, 1 Chia-Hung Kuo, 2 Chih-I Chen, 3 Chung-Cheng Yu, 1 Chwen-Jen Shieh, 2 and Yung-Chuan Liu 1, ⁎ Department of Chemical Engineering, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung, 402, Taiwan, 1 Biotechnology Center, National Chung Hsing University, 250 Kuo-kuang Road, Taichung, 402, Taiwan, 2 and Department of Chemical Engineering, Hsiuping Institute of Technology, 11 Gongye Road, Dali District, Taichung, 412, Taiwan 3 Received 22 July 2011; accepted 30 September 2011 Available online 8 November 2011 In this study, three membranes: regenerated cellulose (RC), glass fiber (GF) and polyvinylidene fluoride (PVDF), were grafted with 1,4-diaminobutane (DA) and activated with glutaraldehyde (GA) for lipase covalent immobilization. The efficiencies of lipases immobilized on these membranes with different hydrophobic/hydrophilic properties were compared. The lipase immobilized on hydrophobic PVDF-DA-GA membrane exhibited more than an 11-fold increase in activity compared to its immobilization on a hydrophilic RC-DA-GA membrane. The relationship between surface hydrophobicity and immobilized efficiencies was investigated using hydrophobic/hydrophilic GF membranes which were prepared by grafting a different ratio of n-butylamine/1,4-diaminobutane (BA/DA). The immobilized lipase activity on the GF membrane increased with the increased BA/DA ratio. This means that lipase activity was exhibited more on the hydrophobic surface. Moreover, the modified PVDF-DA membrane was grafted with GA, epichlorohydrin (EPI) and cyanuric chloride (CC), respectively. The lipase immobilized on the PVDF-DA-EPI membrane displayed the highest specific activity compared to other membranes. This immobilized lipase exhibited more significant stability on pH, thermal, reuse, and storage than did the free enzyme. The results exhibited that the EPI modified PVDF is a promising support for lipase immobilization. © 2011, The Society for Biotechnology, Japan. All rights reserved. [Key words: Lipase; Covalent immobilization; Polyvinylidene fluoride; Hydrophobicity; Surface modification] Lipases (triacylglycerol ester hydrolase, EC 3.1.1.3) are versatile biocatalysts in biological systems capable of catalyzing the hydrolysis of triacylglycerol to glycerol and fatty acids (1) and the reverse synthesis reaction to esters (2). To date, lipases have attracted considerable research interest because of their wide applications, including detergent formulation, oils/fats degradation, pharmaceuti- cals synthesis, biodiesel, and cosmetics production (3). For industrial applications, the immobilization process for lipase always requires improvement of its lifetime and stabilities, reduction of its operation costs and simplification of the purification process (4). A variety of support materials have been used for lipase covalent immobilization. These include: chitosan beads (5), poly(acrylonitrile-co- maleic acid) (6), polyacrylonitrile (7), poly(acrylonitrile-co-2-hydro- xyethyl methacrylate) (8), chitosan/polyvinyl alcohol (9), and poly(acylonitrile-co-acrylic acid) (10). These supporting materials change the microenvironments and enhance the enzyme activity (11-13). For example, Shakeri et al. (14) reported that the specific activity of transesterification reaction by Rhizopus oryzae lipase immobilized on C18- silica-based mesocellular foam was 73 times higher than that of the free enzyme. Palla et al. (15) observed a hyperactivation of lipase from Rhizomucor miehei (about 3-fold) after immobilization on the aliphatic chain of modified chitosan. The membrane-type operation has many advantages, such as no intraparticle diffusion, low-pressure drop, easy operation and mainte- nance, simpler scale-up, etc., over the traditional packed bed reactors (16- 18). Generally, PVDF, RC and GF membranes are commonly employed in microfiltration and ultrafiltration due to their excellent chemical resistance, well-controlled porosity and good thermal property. These membranes have been used as support for various enzymes’ immobili- zation (19-21). However, few reports have been concerned with lipase immobilization on these membrane matrices (12,22,23). Therefore, it was necessary to systematically investigate lipase immobilization on mem- branes with various hydrophobic/hydrophilic (H/H) properties. In this study, three different membranes: RC, GF and PVDF, with different H/H properties were employed for lipase covalent immobili- zation. The effect of H/H surfaces of membranes on the immobilized lipase activity was tested. The immobilized efficiency on GF membranes Journal of Bioscience and Bioengineering VOL. 113 No. 2, 166 – 172, 2012 www.elsevier.com/locate/jbiosc ⁎ Corresponding author. Tel.: + 886 4 22853769; fax: + 886 4 22854734. E-mail address: ycliu@dragon.nchu.edu.tw (Y.-C. Liu). Abbreviations: Al/Am, alkyl/amine tail ratio; BA, n-butylamine; CC, cyanuric chloride; DA, 1,4-diaminobutane; EPI, epichlorohydrin; GA, glutaraldehyde; GF, glass fiber; H/H, hydrophobic/hydrophilic; I/F, immobilization/free; PVDF, polyvinylidene fluoride; RC, regenerated cellulose. 1389-1723/$ - see front matter © 2011, The Society for Biotechnology, Japan. All rights reserved. doi:10.1016/j.jbiosc.2011.09.023