ORIGINAL ARTICLE Enzymatic surface hydrolysis of PET enhances bonding in PVC coating E. ALMANSA 1,2 , S. HEUMANN 1,2 , A. EBERL 1,2 , G. FISCHER-COLBRIE 1 , L. MARTINKOVA 3 , J. MAREK 3 , A. CAVACO-PAULO 4 , & G. M. GUEBITZ 1 1 Department of Environmental Biotechnology, Graz University of Technology, 2 Research Centre Applied Biocatalysis, Graz, Austria, 3 Inotex s.r.o., Czech Republic and 4 Department of Textile Engineering, University of Minho, Portugal Abstract The effect of polyesterase preparations from Thermomyces lanuginosus and Beauveria brongniartii on the hydrophilicity of PET materials was assessed. As a result of polyesterase treatment the hydrophilicity of PET fabrics was increased by up to 8 cm in terms of rising height with increases in surface tension from 6.2 mNm (heat-inactivated control samples) to above 8 mNm. Both enzymes were able to increase the amount of hydroxyl groups on PET from 90 to a maximum of 182 mmol kg 1 , while only the B. brongniartii polyesterase released significant amounts of terephthalic acid from PET. Enzymatic surface hydrolysis of PET increased the bonding strength in PVC coating to 13.40 daN 5cm 1 using 0.5% adhesive compared to 11.5 daN 5cm 1 obtained without enzyme pretreatment and 6% of adhesive. Keywords: Beauveria brongniartii, polyesterase, PVC, PET Introduction PET is the most important polymer used for the production of synthetic textile fibres (Guebitz & Cavaco-Paulo 2008), and also has many other applications ranging from bulk products (plastic bottles) to medical or electronic devices. It has been already reported that enzymes can be used for the hydrolysis and recycling of PET (Mueller 2006). In domestic washing processes of PET based fabrics, polyesterases have shown potential for depil- ling (Yoon et al. 2002). More recently, targeted surface hydrolysis for functionalization of PET fabrics has been reported and PET hydrolysing enzymes were described among cutinases, lipases and esterases. Increased hydrophilicity obtained due to enzymatic surface hydrolysis can improve proper- ties, such as water permeability and wear comfort of PET fabrics. An increased number of hydroxyl and carboxyl groups on the PET surface serve as anchor groups for bonding of molecules that can make finishing processes such as dyeing more efficient (Guebitz & Cavaco-Paulo 2008). Similarly, an increased amount of functional groups on the PET surface could improve coating processes such as in the production of flexible electronic devices (Laskarakis et al. 2008) or with biomaterials in general (Goddard et al. 2007). In coating of PET fabrics with PVC, the bonding strength depends on chemical cross-linking with functional groups on the PET surface. Currently, high amounts of adhesives (up to 10%) are used to obtain a sufficiently high bonding strength suitable for the production of tarpaulins. However, adhesives are both toxic and expensive. In this study, we assessed the potential of two polyesterases, from Thermomyces lanuginosus and Beauveria brongniartii, to insert additional functional groups into PET materials, thereby enhancing bonding strength in PVC coating. Materials and methods Enzymes Beauveria brongniartii was grown on potato dextrose agar (PDA) plates (42 g l 1 ) for 2 days at 308C then stored at 48C. To maintain the viability of the fungus, it was replated every 3 months. The culture medium contained yeast extract (1.5 g l 1 ), glucose (1.0 g l 1 ), MgSO 4 .7H 2 O (4.0 g l 1 ), (NH 4 ) 2 SO 4 (1.0 g l 1 ) KH 2 PO 4 and Na 2 HPO 4 (2.5 g l 1 each) Correspondence: G. M. Guebitz, Department of Environmental Biotechnology, Graz University of Technology, Petersgasse 12, A-8010 Graz, Austria. E-mail: guebitz@tugraz.at Biocatalysis and Biotransformation, SeptemberOctober 2008; 26(5): 365370 ISSN 1024-2422 print/ISSN 1029-2446 online # 2008 Informa UK Ltd DOI: 10.1080/10242420802357613 Downloaded By: [B-on Consortium - 2007] At: 16:03 9 December 2008