Hydrolases polymer modifications

Hydrolase-Catalyzed Modification of Polymers. Terminal hydroxy group of poly(e-CL) was reacted with carboxylic acids using hpase CA catalyst to give end-fimctionalized polyesters (181). Lipase MM catalyzed the regioselec-tive transesterification of the terminal ester group of oligo(methyl methacrylate) with allyl alcohol (201). 

This overview briefly surveys the use of enzymatic and wholecell approaches in polymers. Three types of reactions are covered polymer syntheses, polymer modifications, and polymer hydrolyses. Thus far, most of the enz3une-related R D activities involve hydrolases, oxidoreductases, and transferases, with occasional use of lyases and isomerases. Whole-cell methods continue to be valuable in both academic and industrial labs. All these research areas display continued vitality and creativity, as evidenced by the large number of publications. Advances in biotechnology have provided new and improved enzymes and additional tools. Also included in diis overview is the related topic of biomaterials. 

Enzymes are conunonly classified, via a system of Enzyme Commission (EC) numbers, into six divisions oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases (34). In this work, we are concerned with three types of polymer reactions polymer syntheses, polymer modifications, and polymer degradation and hydrolyses. For these reactions, only hydrolases, oxidoreductases, and transferases are being used extensively in polymers and biomaterials. A summary is given in Table 1. 

Due to the extreme variety of xylan structures, it is obvious that many kinds of enzymes are needed for their complete hydrolysis in nature. Xylanases (EC 3.2.1.8.) are the polysaccharide hydrolases responsible for the attack of the polymer backbone itself. The total hydrolysis or modification of heteroxylans requires in addition several different exo-glycosidases and esterases. The present knowledge of these enzymes is reviewed in this paper. 

Very few reports are available for the enzymatic surface modification of synthetic fibers. Peroxidase, lipase, cutinase, nitrilase, nitrile hydratase, amidase, protease, and hydrolase have been reported for the surface modification of synthetic polymers (Table 4.1). 

Apart from natural materials, oxidoreducates have been used to modify synthetic polymers. For example, using peroxidase, poly(4-hydroxystyrene) has been functionalized with aniline while poly(p-phenylene-2,6-benzobisthiazole) has been rendered more hydrophilic [22, 23]. Other authors have demonstrated that phenolics can be covalently bound to amino-functionalized polymers by using laccase resulting in increased fire resistance [13]A large number of scientific reports are available on enzymatic functionalization of poly(alkyleneterephthalate)s. Polyester fibers account for 73% of all synthetic fibers on the market with an annual production of approx. 27 million tons [24]. Similarly, polyamides and polyacrylonitriles have significant market shares. In contrast to natural polymers discussed above, hydrolases have shown higher potential for modification of these synthetic materials than oxidoreducates. 

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